000
FXUS63 KMQT 062335
AFDMQT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MARQUETTE MI
735 PM EDT SAT SEP 6 2008

UPDATED FOR THE 00Z TAF ISSUANCE

.SYNOPSIS (ISSUED AT 439 PM EDT)...
12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW LARGE SCALE UPR
TROF CENTERED OVER CNTRL NAMERICA BTWN RDGS OFF THE W AND E COASTS.
SHRTWV RESPONSIBLE FOR SHRA LAST NGT/THIS MRNG IS HEADING NEWD INTO
ONTARIO THIS AFTN...AND SUBSIDENCE IN THE WAKE OF THIS SYS HAS
CONTRIBUTED TO THE DVLPMNT OF A MID LVL INVRN ARND H75 AS SHOWN ON
12Z MPX RAOB/15Z TAMDAR SDNG FM RHI THAT IS LIKELY SPREADING NEWD
INTO THE FA BECAUSE THE 12Z RAOB FM GRB SHOWED INVRN BASE AT H65.
DESPITE PLENTY OF LINGERING LLVL MSTR AS SHOWN ON RECENT TAMDAR
SDNGS...THE STRENGTHENING/LOWERING INVRN AS HINTED AS WELL ON RUC
FCST SDNGS HAS CAUSED MOST OF THE SHRA TO DSPT BY 16Z. THE ONLY
EXCEPTIONS ARE OVER THE ERN ZNS...WHERE BACKEDGE OF LINGERING DEEPER
MSTR HAS NOT QUITE PASSED...AND OVER THE W CLOSER TO A WEAKER MID
LVL INVRN AS SHOWN ON THE 12Z INL RAOB. THE W IS ALSO CLOSER TO A
WEAK SFC LO PRESENT JUST W OF CMX AT 15Z. ALTHOUGH THE LOWERING
INVRN HAS TENDED TO DIMINISH THE SHRA...THE TRAPPED LLVL MSTR BLO
THE INVRN BASE HAS RESULTED IN QUITE A BIT OF LO CLD. WHERE SKIES
HAD CLRD EARLIER OVER THE SCNTRL...DAYTIME HTG RESULTED IN THE
DVLPMNT OF MORE LO CLD. THE BACK EDGE OF THIS LO CLD EXTENDS W INTO
CNTRL MN AND S INTO SCNTRL WI. THE 12Z BIS/ABR RAOBS DEPICT A DRIER
SFC-H8 LYR WHERE THERE IS AN ABSENCE OF LO CLD NEAR SFC HI PRES RDG
AXIS. HOWEVER...THERE WAS SOME FOG THIS MRNG IN THAT AREA. ANOTHER
FAIRLY STRONG SHRTWV ROTATING THRU THE MEAN TROF IN THE PLAINS IS
DIGGING THRU SASKATCHEWAN EARLY THIS AFTN. ANOTHER SHRTWV ROUNDING
THE BASE OF THE UPR TROF IS NOTED OVER IA.

&&

.SHORT TERM (TNGT/SUN) (ISSUED AT 439 PM EDT)...

MAIN FCST CONCERNS DURING THIS TIME ARE CLD AND SHRA TRENDS/FOG CHCS
TNGT... THEN TIMING/COVG OF PCPN ON SUN ASSOCIATED WITH SHRTWV NOW
DROPPING THRU SASKATCHEWAN.

FOR TNGT...SHRTWV NOW OVER IA IS PROGGED TO MOVE ENE JUST S OF THE
FA...SO NO CONCERNS ABOUT PCPN ASSOCIATED WITH IT EVEN THOUGH SOME
HI CLD ON ITS NRN FRINGES MAY IMPACT MAINLY THE SCNTRL AND E THRU
MUCH OF THE NGT. OTRW...LARGER SCALE H85-5 QVECTOR DVGC IS FCST TO
DOMINATE THRU THE NGT...WITH SFC HI PRES RDG NOW TO THE W EXPECTED
TO NOSE INTO THE FA OVERNGT. DESPITE THESE EXPECTATIONS...NAM
PERSISTS IN SHOWING LGT QPF OVER THE NCTRL AND E. LOCAL HI RES
MODELS ALSO DEPICT SOME ISOLD SHRA IMPACTING MAINLY THE NCNTRL AND
ERN ZNS DESPITE THE SUSPECTED LARGER SCALE TRENDS. THE GFS SHOWS LTL
IN THE WAY OF QPF. GIVEN THIS DISPARITY IN FCSTS...OPTED TO MAINTAIN
SOME LO CHC POPS OVER THE NRN TIER BEFORE LOSS OF DIURNAL HTG CAUSES
GOING SHRA TO WEAKEN IN ABSENCE OF SGNFT DYNAMIC FORCING. THE SHRA
WL PERSIST LONGEST OVER THE E CLOSER TO DEPARTING LO CENTER MOVING
INTO ERN LK SUP/MORE RESILIENT CYC FLOW. SINCE FOG WAS OBSVD
UPSTREAM LAST NGT CLOSE TO THIS RDG AXIS...WL ADD MENTION OF SOME
FOG LATE TNGT UNDER THE UPR DRYING OVER THE INTERIOR W/SCNTRL CLOSER
TO HI CENTER PASSING TO THE S. SHARPER PRES GRADIENT/WNW FLOW OVER
THE N WL MINIMIZE FOG POTENTIAL...BUT SUSTAIN LO CLD. LOWEST MIN
TEMPS OVER THE INTERIOR NEAR THE WI BORDER WHERE LO LVL WINDS ARE
MOST LIKELY TO DECOUPLE.

ON SUN...SHRTWV OVER SASKATCHEWAN THIS AFTN IS PROGGED TO REACH NRN
MN BY 00Z MON. SFC COLD FNT ASSOCIATED WITH THIS FEATURE WILL REACH
THE CNTRL ZNS LATE IN THE DAY. EXPECT THE DAY TO START ON THE DRY
SIDE WITH FCST SDNGS SHOWING A DRY ATMOSPHERE...BUT APRCH OF SHRTWV/
FNT IN THE AFTN WL INCREASE PCPN CHCS. NEGATIVES FOR PCPN INCLUDE
ABUNDANT DRY AIR...SFC DWPTS THIS AFTN AHEAD OF THE FNT IN THE
DAKOTAS ARE IN THE LOW 40S...AND RELATIVELY WEAK H85 CNVGC ALG THE
BNDRY AS WELL AS ABSENCE OF ANY LARGER SCALE JET FORCING/UPR DVGC.
DESPITE THE NEGATIVES...INTRODUCED CHC TS GIVEN OBSVD LTG STRIKES
UPSTREAM AHD OF THE FNT...GFS/NAM FCST H7-5 LAPSE RATES APRCHG
7C/KM...AND FVRBL PEAK HTG TIME OF DAY FOR ARRIVAL OF BNDRY.
MODIFIED GFS FCST SDNG FOR SFC T/TD OF 70/40 YIELDS A MODEST SBCAPE
UP TO 500 J/KG...BUT STEEP LLVL LAPSE RATES/UNIDIRECTIONAL WLY FLOW
MAY RESULT IN GUSTY WINDS UNDER THE HEAVIER SHRA.

.LONG TERM (SUN NIGHT THRU SAT) (ISSUED AT 439 PM EDT)...

SUN NIGHT...SHORTWAVE BRINGING PCPN TO THE FCST AREA SUN WILL MOVE E
OF THE FCST AREA BY 12Z MON. WILL THUS DIMINISH POPS FROM W TO E
OVERNIGHT SUN NIGHT. THUNDER POTENTIAL WILL ALSO END WITH BOUNDARY
LAYER COOLING. ON MON...IF THERE ARE ANY LINGERING -SHRA OVER THE
E...THEY WILL END IN THE MORNING. ATTENTION THEN TURNS TO NEXT
SHORTWAVE DROPPING INTO THE PLAINS MON AND THEN LIFTING NE INTO THE
GREAT LAKES MON NIGHT. NAM/GFS (ESPECIALLY GFS) ARE STRONGER AND
MORE NRLY WITH ASSOCIATED SFC LOW LIFTING INTO THE GREAT LAEKS. 12Z
UKMET/ECWMF OFFER A MORE SUPPRESSED WEAKER SFC LOW WHILE THE GLOBAL
CANADIAN SHOWS VERY LITTLE SFC REFLECTION AT ALL. AT THIS POINT...
WILL LEAN TOWARD THE MORE CONSISTENT ECMWF SOLUTION WHICH IS
STRONGLY SUPPORTED BY THE UKMET. WEAK GLOBAL CANADIAN SOLUTION ALSO
SUGGESTS LEANING AWAY FROM THE GFS/NAM AT THIS TIME. IMPRESSIVE
UPPER DIVERGENCE IN RIGHT ENTRANCE OF 300MB JET WILL YIELD A
SIGNIFICANT STRIPE OF PCPN LIFTING INTO THE GREAT LAKES N OF SFC LOW
TRACK. HOWEVER...IN FAVORING THE FLATTER ECMWF/UKMET SOLUTION...BULK
OF THAT RAIN WILL PASS BY TO THE SE OF THE FCST AREA MON NIGHT.
SHOULD A MORE NRLY SOLUTION PAN OUT...A MUCH NEEDED WIDESPREAD
RAINFALL WOULD DEVELOP OVER THE FCST AREA. GRIDS WILL BE STRUCTURED
TO SHOW HIGHEST POPS SE (STILL JUST CHC CATEGORY) WITH DRY WEATHER
NW MON AFTN/NIGHT.

WED THRU SAT...MEDIUM RANGE MODELS (ECMWF/UKMET/CANADIAN/GFS) ARE IN
GOOD AGREEMENT ON THE OVERALL PATTERN OVER NAMERICA DURING THIS TIME
FRAME. ALL FEATURE A PROGRESSIVE REGIME ACROSS THE NRN CONUS TO THE
S OF THE POLAR VORTEX CENTERING ITSELF OVER NCNTRL CANADA. THERE IS
ONE MAIN SHORTWAVE TROF OF INTEREST THAT WILL SWING ACROSS THE NRN
CONUS...AND MEDIUM RANGE MODELS HAVE BEEN AND CONTINUE TO BE IN
QUITE GOOD AGREEMENT ON TIMING THE TROF. GIVEN AGREEMENT ON THE
OVERALL PATTERN AND INDIVIDUAL FEATURES...CONFIDENCE DURING THE
WED-SAT PERIOD IS ABOVE NORMAL. SFC HIGH PRES OVER THE WRN GREAT
LAKES TUE NIGHT WILL SLIP QUICKLY TO THE E. WITH HIGH PRES OVER THE
FCST AREA FOR AT LEAST THE EARLY PART OF TUE NIGHT...WILL GO AT OR
BLO THE LOW END OF MOS GUIDANCE FOR MINS...ESPECIALLY OVER THE E.
MAY SEE SOME PATCHY FROST INTERIOR CNTRL AND E. ON WED...SFC LOW
PRES TROF WILL EMERGE OVER THE WRN PLAINS IN RESPONSE TO THE
APPROACHING SHORTWAVE TROF. WAA PATTERN WILL DEVELOP WED...THOUGH IT
APPEARS THE BEST WAA WILL STILL REMAIN W AND SW OF THE FCST AREA
THRU THE DAY. IN ADDITION...LOW-LEVEL FLOW REMAINS SOMEWHAT
ANTICYCLONIC...ESPECIALLY AS DEPICTED IN THE ECWMF. FOR THESE
REASONS...CONSIDERED REMOVING POPS FROM ALL BUT WRN LAKE SUPERIOR.
FOR NOW...WILL TRIM POPS BACK FROM THE INHERITED FCST TO INCLUDE
JUST THE FAR WRN FCST AREA WED AFTN. SHRA/TSRA WILL THEN PROGRESS E
ACROSS THE FCST AREA WED NIGHT/THU. WITH 12HR HEIGHT FALLS NEARING
100M AND A NICE RIBBON OF DEEP MOISTURE...THIS SYSTEM OFFERS THE
POTENTIAL FOR WIDESPREAD MUCH NEEDED PCPN THOUGH QUICK MOVEMENT WILL
WORK TO LIMIT AMOUNTS. FOR NOW...DID NOT GO ANY HIGHER THAN THE HIGH
CHC RANGE AS MODEL TIMING CHANGES OF 12HRS OR MORE ARE CERTAINLY
POSSIBLE 4-6 DAYS OUT INTO MODEL RUNS. EVENTUALLY...HIGH POPS SHOULD
BE REQUIRED ONCE TIMING IS CERTAIN. ALTHOUGH SOME -SHRA/SPRINKLES
MAY LINGER INTO FRI MORNING IN BACKSIDE CYCLONIC FLOW...WILL DRY
FCST OUT FOR FRI/SAT IN THE WAKE OF SYSTEM. AS FOR TEMPS...READINGS
THRU THE PERIOD SHOULD NOT STRAY TOO FAR FROM NORMAL FOR EARLY/MID
SEPT.

&&

.AVIATION (FOR THE 00Z TAF ISSUANCE)...

MVFR CEILINGS WILL LIKELY REDEVELOP TEMPORARILY AT CMX AS WESTERLY
UPSLOPE WINDS TAKE HOLD OVERNIGHT. EXPECTE IMPROVING CONDITIONS AT
SAW AS LIGHT SHOWERS EXIT.  HOWEVER...WILL NEED TO MONITOR THE THE
POSSIBILITY OF FOG AT SAW.

&&

.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...

EXPECT LOW PRESSURE OVER WESTERN UPPER MICHIGAN TO DRIFT INTO
EASTERN LAKE SUPERIOR OVERNIGHT. IN ITS WAKE...A WEAK 30.0 INCH
RIDGE OF HIGH PRESSURE WILL CROSS LAKE SUPERIOR LATE TONIGHT INTO
SUNDAY MORNING. WINDS OVER THE LAKE WILL BE LIGHT DURING THIS
PERIOD. A 29.9 INCH LOW PRESSURE OVER NORTHWEST ONTARIO EARLY SUNDAY
MORNING WILL MOVE OVER JAMES BAY LATE SUNDAY NIGHT...DRAGGING A COLD
FRONT ACROSS LAKE SUPERIOR. NORTHWEST WINDS BEHIND THIS FRONT WILL
INCREASE TO 30 KNOTS OVER THE EAST HALF OF LAKE SUPERIOR. A LOW WILL
FORM OVER NORTHERN ILLINOIS MONDAY EVENING AND DEEPEN TO AS IT MOVES
INTO WESTERN QUEBEC ON TUESDAY. LOOK FOR HIGH PRESSURE TO BUILD OVER
THE CENTRAL PLAINS AND MINNESOTA TUESDAY AFTERNOON AND MOVE TO THE
EASTERN GREAT LAKES WEDNESDAY EVENING. A LOW PRESSURE TROUGH...
EXTENDING FROM WESTERN ONTARIO TO THE CENTRAL PLAINS WEDNESDAY
EVENING...WILL CROSS LAKE SUPERIOR THURSDAY.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

SYNOPSIS/SHORT TERM...KC
LONG TERM...ROLFSON
AVIATION...KF
MARINE...KC

000
FXUS63 KDTX 062304
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
704 PM EDT SAT SEP 6 2008


.AVIATION...

A SURFACE RIDGE AND DRY AIR WILL MAINTAIN VFR CONDITIONS AND
LIGHT WINDS THROUGH THE REMAINDER OF THE EVENING. AN AREA OF LIGHT
RAIN CURRENTLY ACROSS NORTHERN MISSOURI IS ASSOCIATED WITH AN
ELEVATED FRONTAL BOUNDARY. THIS SYSTEM WILL TRACK ACROSS SOUTHERN
MICHIGAN BETWEEN 06Z AND 15Z. LINGERING LOW LEVEL DRY AIR SHOULD
INITIALLY INHIBIT MUCH PRECIP FROM REACHING THE SURFACE.
HOWEVER...PERSISTENT LARGE SCALE FORCING SHOULD ALLOW RAIN TO
DEVELOP AT OR SHORTLY AFTER 09Z. MODEL SOUNDINGS INDICATE THAT
MOISTENING OF THE LOW LEVELS WILL RESULT IN MVFR CIGS AND VSBY IN
LIGHT RAIN AROUND 12Z...PERSISTING TO 15Z. CONDITIONS WILL QUICKLY
IMPROVE AFTER 15Z AS LARGE SCALE SUBSIDENCE BUILDS ACROSS SE MI IN
THE WAKE OF THIS SYSTEM.

&&

.PREV DISCUSSION...ISSUED 353 PM EDT SAT SEP 6 2008

SHORT TERM...THROUGH TONIGHT

FOR THE VERY NEAR TERM...A WEAK SURFACE TROUGH CONTINUES TO GENERATE
A FEW SHOWERS OVER NORTHERN AND CENTRAL MICHIGAN. THE TAIL END OF
THIS ACTIVITY IS EXPECTED TO AFFECT THE TRI-CITIES AND THUMB REGION
LATE THIS AFTERNOON AND EARLY EVENING...BRINGING ONLY A THREAT FOR
ISOLATED SHOWERS. MODELS HAVE BEEN VERY CONSISTENT WITH WEAKENING
THE LOW-LEVEL THERMAL TROUGH ASSOCIATED WITH THIS FEATURE AS IT
CROSSES THE STATE...AND WILL THEREFORE KEEP CHANCES FOR RAIN OUT OF
THE THUMB THIS EVENING.

SIGNIFICANT CHANGE WAS MADE TO THE OVERNIGHT FORECAST AS THE STRONG
SHORTWAVE TROUGH CURRENTLY OVER CENTRAL NEBRASKA IS NOW FORECAST TO
LIFT NORTHEAST AND THROUGH LOWER MICHIGAN LATE TONIGHT AND EARLY
TOMORROW. SO FAR IN THE CENTRAL PLAINS TODAY...THIS SHORTWAVE HAS
BEEN GENERATING SHOWERS AHEAD OF AND JUST SOUTH OF IT AS THE
DISTURBANCE RIDES ALONG AN H850-700 BAROCLINIC ZONE WHICH STRETCHES
FROM KANSAS/NEBRASKA UP INTO THE SOUTHERN GREAT LAKES. ALTHOUGH ONLY
A MODEST INCREASE IN MOISTURE IS EXPECTED LATE TONIGHT...LIFT WILL
BE ENHANCED BY SOME LEFT EXIT REGION DYNAMICS...AND HELP TO MAKE
THE BEST OF AVAILABLE MOISTURE. EXPECT TO SEE PRECIPITATION FROM
THIS SYSTEM SPREAD INTO SOUTHEAST MICHIGAN VERY LATE TONIGHT AND
CONTINUE TO FUNNEL IN THROUGH THE OVERNIGHT HOURS. WITH THE EXPECTED
INCREASE IN CLOUD COVER AND PRECIPITATION...HAD TO BUMP FORECAST
MINS UP A FEW DEGREES...BUT READINGS ARE STILL EXPECTED TO BE IN THE
50S.

LONG TERM...SUNDAY THROUGH NEXT SATURDAY

MOISTURE LADEN AIRMASS WILL LINGER ACROSS THE FORECAST AREA SUNDAY
MORNING.  THE COMBINATION OF ADEQUATE MOISTURE TRANSPORT AND
MID-LEVEL /850-600MB/ FGEN WILL SUPPORT CONTINUED SHOWER
DEVELOPMENT.  BOTH THE GFS AND NAM ARE ADVERTISING SOME WEAK
ELEVATED INSTABILITY...ENOUGH TO SUPPORT A MENTIONABLE CHANCE FOR
THUNDER AS THE STRONGEST DYNAMICS SWING THROUGH.  MID-LEVEL HEIGHTS
WILL BUILD QUICKLY...SUPPORTING DEEP LAYER SUBSIDENCE LATER IN THE
DAY.   THIS SHOULD HELP SCOUR THE CLOUDS OUT SUBSTANTIALLY...IN
SPITE OF SOME SIGNS OF RESIDUAL MOISTURE BELOW 700MB.  THEREFORE...
EXPECT TEMPS TO RECOVER INTO THE LOW-MID 70S.

NWP SOLUTIONS ARE TRENDING TOWARD CONTRACTING THE WAVELENGTH OF THE
NEXT SHORTWAVE AS IT APPROACHES THE LAKES REGION LATE MONDAY -
RESULTING IN MORE AMPLIFICATION. THE NCEP PROGS ARE CERTAINLY
FAVORING GREATER DEVELOPMENT - THE GFS BEING THE STRONGEST -
COMPARED TO THE IMPORTED SOLUTIONS. HOWEVER...THE NEW ECMWF IS ALSO
TRENDING STRONGER - THOUGH STILL TEMPERED COMPARED TO THE GFS/NAM
DEPICTIONS.  FURTHERMORE...THE VAST MAJORITY OF THE 12Z GEFS MEMBERS
ARE FAVORING A SOLUTION THAT IS MUCH MORE AMPLIFIED.  EXPECT THE
STRONGER SOLUTION TO RESULT IN A SLIGHTLY SLOWER PROGRESSION OF THE
KEY PLAYERS. THEREFORE...WILL RETARD THE ONSET OF PRECIP CHANCES TO
LATE ON MONDAY...WITH THE BEST OPPORTUNITY MONDAY NIGHT LINGERING
INTO TUESDAY MORNING. GREATER DEVELOPMENT OF THE WAVE ALSO OPENS THE
DOOR TO ADVECT AN AIRMASS WITH MORE INSTABILITY INTO THE FORECAST
AREA AS WELL - THUS WILL INTRODUCE THUNDER TO THE FORECAST.

THE LARGE SCALE FLOW REGIME WILL REMAIN QUITE PROGRESSIVE THROUGH
THE REMAINDER OF THE WEEK...WHICH WILL KEEP HIGHS QUITE SEASONABLE.
THE NEXT DISCERNIBLE SHORTWAVE IS EXPECTED TO AFFECT THE REGION
THURSDAY AND FRIDAY.

MARINE...

SOUTHWESTERLY WINDS WILL BE ON THE INCREASE SUNDAY AS A SURFACE
TROUGH MOVES THROUGH THE REGION.  THIS WILL SET THE STAGE FOR HIGHER
WAVES ON SAGINAW BAY - BUT NOT EXPECTING CONDITIONS TO DETERIORATE
TO ADVISORY CRITERIA.  A LOW PRESSURE IS PROJECTED TO TRAVERSE THE
LAKES REGION ON TUESDAY AND IS EXPECTED TO STRENGTHEN DURING THAT
TIME.  AS A RESULT NORTHWESTERLY GALE FORCE WINDS ARE POSSIBLE
TUESDAY AND TUESDAY NIGHT ACROSS LAKE HURON AS THE LOW DEPARTS THE
REGION.  WINDS AND WAVES SHOULD SUBSIDE RATHER QUICKLY BY LATE
WEDNESDAY AS HIGH PRESSURE BUILDS BACK INTO THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....SC
SHORT TERM...HLO
LONG TERM....MANN
MARINE.......MANN


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

000
FXUS63 KMQT 062040
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
439 PM EDT SAT SEP 6 2008

.SYNOPSIS...
12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW LARGE SCALE UPR
TROF CENTERED OVER CNTRL NAMERICA BTWN RDGS OFF THE W AND E COASTS.
SHRTWV RESPONSIBLE FOR SHRA LAST NGT/THIS MRNG IS HEADING NEWD INTO
ONTARIO THIS AFTN...AND SUBSIDENCE IN THE WAKE OF THIS SYS HAS
CONTRIBUTED TO THE DVLPMNT OF A MID LVL INVRN ARND H75 AS SHOWN ON
12Z MPX RAOB/15Z TAMDAR SDNG FM RHI THAT IS LIKELY SPREADING NEWD
INTO THE FA BECAUSE THE 12Z RAOB FM GRB SHOWED INVRN BASE AT H65.
DESPITE PLENTY OF LINGERING LLVL MSTR AS SHOWN ON RECENT TAMDAR
SDNGS...THE STRENGTHENING/LOWERING INVRN AS HINTED AS WELL ON RUC
FCST SDNGS HAS CAUSED MOST OF THE SHRA TO DSPT BY 16Z. THE ONLY
EXCEPTIONS ARE OVER THE ERN ZNS...WHERE BACKEDGE OF LINGERING DEEPER
MSTR HAS NOT QUITE PASSED...AND OVER THE W CLOSER TO A WEAKER MID
LVL INVRN AS SHOWN ON THE 12Z INL RAOB. THE W IS ALSO CLOSER TO A
WEAK SFC LO PRESENT JUST W OF CMX AT 15Z. ALTHOUGH THE LOWERING
INVRN HAS TENDED TO DIMINISH THE SHRA...THE TRAPPED LLVL MSTR BLO
THE INVRN BASE HAS RESULTED IN QUITE A BIT OF LO CLD. WHERE SKIES
HAD CLRD EARLIER OVER THE SCNTRL...DAYTIME HTG RESULTED IN THE
DVLPMNT OF MORE LO CLD. THE BACK EDGE OF THIS LO CLD EXTENDS W INTO
CNTRL MN AND S INTO SCNTRL WI. THE 12Z BIS/ABR RAOBS DEPICT A DRIER
SFC-H8 LYR WHERE THERE IS AN ABSENCE OF LO CLD NEAR SFC HI PRES RDG
AXIS. HOWEVER...THERE WAS SOME FOG THIS MRNG IN THAT AREA. ANOTHER
FAIRLY STRONG SHRTWV ROTATING THRU THE MEAN TROF IN THE PLAINS IS
DIGGING THRU SASKATCHEWAN EARLY THIS AFTN. ANOTHER SHRTWV ROUNDING
THE BASE OF THE UPR TROF IS NOTED OVER IA.

&&

.SHORT TERM (TNGT/SUN)...

MAIN FCST CONCERNS DURING THIS TIME ARE CLD AND SHRA TRENDS/FOG CHCS
TNGT... THEN TIMING/COVG OF PCPN ON SUN ASSOCIATED WITH SHRTWV NOW
DROPPING THRU SASKATCHEWAN.

FOR TNGT...SHRTWV NOW OVER IA IS PROGGED TO MOVE ENE JUST S OF THE
FA...SO NO CONCERNS ABOUT PCPN ASSOCIATED WITH IT EVEN THOUGH SOME
HI CLD ON ITS NRN FRINGES MAY IMPACT MAINLY THE SCNTRL AND E THRU
MUCH OF THE NGT. OTRW...LARGER SCALE H85-5 QVECTOR DVGC IS FCST TO
DOMINATE THRU THE NGT...WITH SFC HI PRES RDG NOW TO THE W EXPECTED
TO NOSE INTO THE FA OVERNGT. DESPITE THESE EXPECTATIONS...NAM
PERSISTS IN SHOWING LGT QPF OVER THE NCTRL AND E. LOCAL HI RES
MODELS ALSO DEPICT SOME ISOLD SHRA IMPACTING MAINLY THE NCNTRL AND
ERN ZNS DESPITE THE SUSPECTED LARGER SCALE TRENDS. THE GFS SHOWS LTL
IN THE WAY OF QPF. GIVEN THIS DISPARITY IN FCSTS...OPTED TO MAINTAIN
SOME LO CHC POPS OVER THE NRN TIER BEFORE LOSS OF DIURNAL HTG CAUSES
GOING SHRA TO WEAKEN IN ABSENCE OF SGNFT DYNAMIC FORCING. THE SHRA
WL PERSIST LONGEST OVER THE E CLOSER TO DEPARTING LO CENTER MOVING
INTO ERN LK SUP/MORE RESILIENT CYC FLOW. SINCE FOG WAS OBSVD
UPSTREAM LAST NGT CLOSE TO THIS RDG AXIS...WL ADD MENTION OF SOME
FOG LATE TNGT UNDER THE UPR DRYING OVER THE INTERIOR W/SCNTRL CLOSER
TO HI CENTER PASSING TO THE S. SHARPER PRES GRADIENT/WNW FLOW OVER
THE N WL MINIMIZE FOG POTENTIAL...BUT SUSTAIN LO CLD. LOWEST MIN
TEMPS OVER THE INTERIOR NEAR THE WI BORDER WHERE LO LVL WINDS ARE
MOST LIKELY TO DECOUPLE.

ON SUN...SHRTWV OVER SASKATCHEWAN THIS AFTN IS PROGGED TO REACH NRN
MN BY 00Z MON. SFC COLD FNT ASSOCIATED WITH THIS FEATURE WILL REACH
THE CNTRL ZNS LATE IN THE DAY. EXPECT THE DAY TO START ON THE DRY
SIDE WITH FCST SDNGS SHOWING A DRY ATMOSPHERE...BUT APRCH OF SHRTWV/
FNT IN THE AFTN WL INCREASE PCPN CHCS. NEGATIVES FOR PCPN INCLUDE
ABUNDANT DRY AIR...SFC DWPTS THIS AFTN AHEAD OF THE FNT IN THE
DAKOTAS ARE IN THE LOW 40S...AND RELATIVELY WEAK H85 CNVGC ALG THE
BNDRY AS WELL AS ABSENCE OF ANY LARGER SCALE JET FORCING/UPR DVGC.
DESPITE THE NEGATIVES...INTRODUCED CHC TS GIVEN OBSVD LTG STRIKES
UPSTREAM AHD OF THE FNT...GFS/NAM FCST H7-5 LAPSE RATES APRCHG
7C/KM...AND FVRBL PEAK HTG TIME OF DAY FOR ARRIVAL OF BNDRY.
MODIFIED GFS FCST SDNG FOR SFC T/TD OF 70/40 YIELDS A MODEST SBCAPE
UP TO 500 J/KG...BUT STEEP LLVL LAPSE RATES/UNIDIRECTIONAL WLY FLOW
MAY RESULT IN GUSTY WINDS UNDER THE HEAVIER SHRA.

.LONG TERM (SUN NIGHT THRU SAT)...

SUN NIGHT...SHORTWAVE BRINGING PCPN TO THE FCST AREA SUN WILL MOVE E
OF THE FCST AREA BY 12Z MON. WILL THUS DIMINISH POPS FROM W TO E
OVERNIGHT SUN NIGHT. THUNDER POTENTIAL WILL ALSO END WITH BOUNDARY
LAYER COOLING. ON MON...IF THERE ARE ANY LINGERING -SHRA OVER THE
E...THEY WILL END IN THE MORNING. ATTENTION THEN TURNS TO NEXT
SHORTWAVE DROPPING INTO THE PLAINS MON AND THEN LIFTING NE INTO THE
GREAT LAKES MON NIGHT. NAM/GFS (ESPECIALLY GFS) ARE STRONGER AND
MORE NRLY WITH ASSOCIATED SFC LOW LIFTING INTO THE GREAT LAEKS. 12Z
UKMET/ECWMF OFFER A MORE SUPPRESSED WEAKER SFC LOW WHILE THE GLOBAL
CANADIAN SHOWS VERY LITTLE SFC REFLECTION AT ALL. AT THIS POINT...
WILL LEAN TOWARD THE MORE CONSISTENT ECMWF SOLUTION WHICH IS
STRONGLY SUPPORTED BY THE UKMET. WEAK GLOBAL CANADIAN SOLUTION ALSO
SUGGESTS LEANING AWAY FROM THE GFS/NAM AT THIS TIME. IMPRESSIVE
UPPER DIVERGENCE IN RIGHT ENTRANCE OF 300MB JET WILL YIELD A
SIGNIFICANT STRIPE OF PCPN LIFTING INTO THE GREAT LAKES N OF SFC LOW
TRACK. HOWEVER...IN FAVORING THE FLATTER ECMWF/UKMET SOLUTION...BULK
OF THAT RAIN WILL PASS BY TO THE SE OF THE FCST AREA MON NIGHT.
SHOULD A MORE NRLY SOLUTION PAN OUT...A MUCH NEEDED WIDESPREAD
RAINFALL WOULD DEVELOP OVER THE FCST AREA. GRIDS WILL BE STRUCTURED
TO SHOW HIGHEST POPS SE (STILL JUST CHC CATEGORY) WITH DRY WEATHER
NW MON AFTN/NIGHT.

WED THRU SAT...MEDIUM RANGE MODELS (ECMWF/UKMET/CANADIAN/GFS) ARE IN
GOOD AGREEMENT ON THE OVERALL PATTERN OVER NAMERICA DURING THIS TIME
FRAME. ALL FEATURE A PROGRESSIVE REGIME ACROSS THE NRN CONUS TO THE
S OF THE POLAR VORTEX CENTERING ITSELF OVER NCNTRL CANADA. THERE IS
ONE MAIN SHORTWAVE TROF OF INTEREST THAT WILL SWING ACROSS THE NRN
CONUS...AND MEDIUM RANGE MODELS HAVE BEEN AND CONTINUE TO BE IN
QUITE GOOD AGREEMENT ON TIMING THE TROF. GIVEN AGREEMENT ON THE
OVERALL PATTERN AND INDIVIDUAL FEATURES...CONFIDENCE DURING THE
WED-SAT PERIOD IS ABOVE NORMAL. SFC HIGH PRES OVER THE WRN GREAT
LAKES TUE NIGHT WILL SLIP QUICKLY TO THE E. WITH HIGH PRES OVER THE
FCST AREA FOR AT LEAST THE EARLY PART OF TUE NIGHT...WILL GO AT OR
BLO THE LOW END OF MOS GUIDANCE FOR MINS...ESPECIALLY OVER THE E.
MAY SEE SOME PATCHY FROST INTERIOR CNTRL AND E. ON WED...SFC LOW
PRES TROF WILL EMERGE OVER THE WRN PLAINS IN RESPONSE TO THE
APPROACHING SHORTWAVE TROF. WAA PATTERN WILL DEVELOP WED...THOUGH IT
APPEARS THE BEST WAA WILL STILL REMAIN W AND SW OF THE FCST AREA
THRU THE DAY. IN ADDITION...LOW-LEVEL FLOW REMAINS SOMEWHAT
ANTICYCLONIC...ESPECIALLY AS DEPICTED IN THE ECWMF. FOR THESE
REASONS...CONSIDERED REMOVING POPS FROM ALL BUT WRN LAKE SUPERIOR.
FOR NOW...WILL TRIM POPS BACK FROM THE INHERITED FCST TO INCLUDE
JUST THE FAR WRN FCST AREA WED AFTN. SHRA/TSRA WILL THEN PROGRESS E
ACROSS THE FCST AREA WED NIGHT/THU. WITH 12HR HEIGHT FALLS NEARING
100M AND A NICE RIBBON OF DEEP MOISTURE...THIS SYSTEM OFFERS THE
POTENTIAL FOR WIDESPREAD MUCH NEEDED PCPN THOUGH QUICK MOVEMENT WILL
WORK TO LIMIT AMOUNTS. FOR NOW...DID NOT GO ANY HIGHER THAN THE HIGH
CHC RANGE AS MODEL TIMING CHANGES OF 12HRS OR MORE ARE CERTAINLY
POSSIBLE 4-6 DAYS OUT INTO MODEL RUNS. EVENTUALLY...HIGH POPS SHOULD
BE REQUIRED ONCE TIMING IS CERTAIN. ALTHOUGH SOME -SHRA/SPRINKLES
MAY LINGER INTO FRI MORNING IN BACKSIDE CYCLONIC FLOW...WILL DRY
FCST OUT FOR FRI/SAT IN THE WAKE OF SYSTEM. AS FOR TEMPS...READINGS
THRU THE PERIOD SHOULD NOT STRAY TOO FAR FROM NORMAL FOR EARLY/MID
SEPT.

&&

.AVIATION (FOR THE 18Z TAF ISSUANCE)...

EXPECT MVFR CIGS TO PERSIST AT LEAST OCCASIONALLY AT BOTH SITES THE
REST OF THIS AFTN WITH LINGERING LLVL MSTR SHOWN ON RECENT TAMDAR
SDNGS/SMALL SFC DWPT DEPRESSIONS IN THE PRESENCE OF DIURNAL HTG. BUT
THE TREND SHOULD BE FOR A GRDL IMPROVEMENT WITH THIS SFC HTG LIFTING
THE CIG BASE. MVFR CIGS WL LIKELY REDVLP AT CMX TNGT WITH EXPECTED
UPSLOPE WLY FLOW AND DIURNAL COOLING BEFORE THE ARRIVAL OF DRIER AIR
NOW IN WRN MN TENDS TO BREAK UP ANY LO CLD. SAW WL BE MORE SHELTERED
FM THIS FLOW...SO RADIATION FOG IS A POSSIBILITY THERE. THEN VFR
CONDITIONS WL BE THE RULE AFT ANY MRNG FOG BURNS OFF AT SAW ON SUN
THRU 18Z.

&&

.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...

EXPECT LOW PRESSURE OVER WESTERN UPPER MICHIGAN TO DRIFT INTO
EASTERN LAKE SUPERIOR OVERNIGHT. IN ITS WAKE...A WEAK 30.0 INCH
RIDGE OF HIGH PRESSURE WILL CROSS LAKE SUPERIOR LATE TONIGHT INTO
SUNDAY MORNING. WINDS OVER THE LAKE WILL BE LIGHT DURING THIS
PERIOD. A 29.9 INCH LOW PRESSURE OVER NORTHWEST ONTARIO EARLY SUNDAY
MORNING WILL MOVE OVER JAMES BAY LATE SUNDAY NIGHT...DRAGGING A COLD
FRONT ACROSS LAKE SUPERIOR. NORTHWEST WINDS BEHIND THIS FRONT WILL
INCREASE TO 30 KNOTS OVER THE EAST HALF OF LAKE SUPERIOR. A LOW WILL
FORM OVER NORTHERN ILLINOIS MONDAY EVENING AND DEEPEN TO AS IT MOVES
INTO WESTERN QUEBEC ON TUESDAY. LOOK FOR HIGH PRESSURE TO BUILD OVER
THE CENTRAL PLAINS AND MINNESOTA TUESDAY AFTERNOON AND MOVE TO THE
EASTERN GREAT LAKES WEDNESDAY EVENING. A LOW PRESSURE TROUGH...
EXTENDING FROM WESTERN ONTARIO TO THE CENTRAL PLAINS WEDNESDAY
EVENING...WILL CROSS LAKE SUPERIOR THURSDAY.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

SYNOPSIS/SHORT TERM...KC
LONG TERM...ROLFSON
AVIATION...KC
MARINE...KC

000
FXUS63 KGRR 062017
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
400 PM EDT SAT SEP 6 2008

LATEST UPDATE...ALL SECTIONS BUT AVIATION...

.SYNOPSIS...(400 PM EDT SAT SEP 6 2008)
AN UPPER LEVEL DISTURBANCE OVER THE CENTRAL PLAINS WILL MOVE
NORTHEAST AND CROSS SOUTHERN LOWER MICHIGAN LATE TONIGHT. THIS
FEATURE WILL BRING AN INCREASED CHANCE OF RAIN AFTER MIDNIGHT AND
EARLY SUNDAY MORNING... PARTICULARLY SOUTH OF INTERSTATE 96.

A FRONTAL BOUNDARY WILL APPROACH FROM THE WEST SUNDAY NIGHT THEN
STALL FROM SOUTHERN LOWER MICHIGAN TO THE CENTRAL PLAINS ON MONDAY.
A LOW PRESSURE SYSTEM WILL FORM AND INTENSIFY ALONG THIS FRONT
MONDAY NIGHT... BRINGING ANOTHER INCREASED CHANCE OF RAIN TO
SOUTHERN AND CENTRAL LOWER MICHIGAN.

&&

.SHORT TERM...(1150 AM EDT SAT SEP 6 2008)
(TONIGHT THROUGH MONDAY NIGHT)
RECENT MODEL RUNS HAVE BEEN CONVERGING ON A SOLUTION OF A HIGHER
PROBABILITY OF RAIN SHOWERS LATE TONIGHT AND SUNDAY MORNING OVER THE
SRN CWFA. THIS IS IN RESPONSE TO STRONG UPR LEVEL DIVERGENCE AND MID
LEVEL FGEN WITHIN A COUPLED JET STRUCTURE ALOFT. THIS RAIN APPEARS
TO MOVE OUT OF THE AREA BY 18Z SUNDAY WITH DRY WEATHER LIKELY
THEREAFTER.

THE NEXT BIG WEATHER MAKER APPEARS TO TAKE AIM ON THE AREA MONDAY
AFTERNOON AND NIGHT. A FRONTAL BOUNDARY WILL BE SITUATED FROM LOWER
MICHIGAN INTO THE CENTRAL PLAINS DURING THIS TIME AND WILL SHARPEN
AS H5 TROUGH DIGS UPSTREAM. MODELS ARE NOT IN GREAT AGREEMENT ON THE
TIMING... TRACK... AND STRENGTH OF SFC WAVE MOVING NE ALONG THE
FRONT. ATTM PREFER THE ECMWF SOLN WHICH HAS BEEN VERY CONSISTENT.

TEMPS/CLOUDS/POPS ARE VERY TRICKY ON MONDAY SINCE SHARPENING FRONTAL
BOUNDARY WILL PROBABLY BE RIGHT OVER THE CWFA. THIS MAY LEAD TO COOL
AND SHOWERY CONDITIONS IN THE NRN CWFA AND MUCH WARMER AND DRY
CONDITIONS IN THE SOUTH. WILL HAVE POPS RANGING FROM 30 PCT IN THE
SE CWFA TO 50 PCT IN THE NW MONDAY... INCREASING TO LIKELY /60 PCT/
OVER THE ENTIRE CWFA MONDAY NIGHT. COULD BE ANOTHER GOOD SOAKING
RAIN ALTHOUGH NOT NEARLY THE QPF AMOUNTS WE SAW FROM GUSTAV.

&&

.LONG TERM...(400 PM EDT SAT SEP 6 2008)
TUESDAY THROUGH SATURDAY)
COOLER AIR WILL BE MOVING INTO THE CWA AS THE EXTENDED PERIOD BEGINS
TUESDAY. SHOWERS WILL END OVER THE ERN CWA TUESDAY MORNING...THEN
WE/LL HAVE A COUPLE OF DRY DAYS BEFORE THE SFC HIGH MOVES EAST AND
ANOTHER LOW HEADS TOWARD LOWER MICHIGAN. THE SOUTH FLOW AHEAD OF IT
WILL BOOST TEMPS BACK INTO THE MID 70S. WE/LL KEEP TSRA/SHRA IN THE
GRIDS THURSDAY AND FRIDAY AS THE FRONT MOVES THROUGH AND THEN THE
IMPRESSIVE CLOSED LOW FOLLOWS. INSTABILITY DOESN/T LOOK ALL THAT
IMPRESSIVE...BUT SOME OF THE JUICE FOR CONVECTIVE DEVELOPMENT WILL
BE MADE UP BY THE STRONG MOISTURE CONVERGENCE ALONG THE FRONT.  DRY
WX EXPECTED SATURDAY.

&&

.MARINE...(400 PM EDT SAT SEP 6 2008)
WINDS/WAVES SHOULD STAY BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH
MONDAY. MONDAY NIGHT AND TUESDAY MAY TURN VERY ROUGH ON LAKE
MICHIGAN DEPENDING ON INTENSITY... TIMING... AND TRACK OF
DEVELOPING/DEEPENING LOW PRESSURE SYSTEM ALONG THE STALL FRONTAL
BOUNDARY.

&&

.AVIATION...(131 PM EDT SAT SEP 6 2008)
SHOWERS WILL DIMINISH ACROSS THE NRN CWA THIS AFTERNOON. MUCH OF THE
CWA WILL SEE SCT CU THIS AFTERNOON. AN UPPER LOW WILL MOVE ACROSS
THE REGION LATE TONIGHT AND EARLY SUNDAY. THIS MAY GENERATE SHOWERS
ACROSS THE CWA. TAF SITES SHOULD REMAIN VFR.

&&

.HYDROLOGY...(400 PM EDT SAT SEP 6 2008)
QPF AMOUNTS TONIGHT ARE PROGGED TO BE A QUARTER INCH OR LESS... WITH
MAX AMOUNTS EXPECTED TO BE SOUTH OF A LINE FROM SOUTH HAVEN TO
LANSING. THIS WILL HAVE LITTLE OR NO IMPACT ON HYDRO. THE SYSTEM ON
MONDAY NIGHT LOOKS TO HAVE THE POTENTIAL OF PRODUCING WIDESPREAD
AMOUNTS OF AROUND ONE HALF INCH... WITH LOCAL AMOUNTS OF UP TO ONE
INCH POSSIBLE.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.

&&

$$

SYNOPSIS:     MEADE
SHORT TERM:   MEADE
LONG TERM:    93
MARINE:       MEADE
AVIATION:     93
HYDROLOGY:    MEADE

000
FXUS63 KDTX 061953
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
353 PM EDT SAT SEP 6 2008

.SHORT TERM...THROUGH TONIGHT

FOR THE VERY NEAR TERM...A WEAK SURFACE TROUGH CONTINUES TO GENERATE
A FEW SHOWERS OVER NORTHERN AND CENTRAL MICHIGAN. THE TAIL END OF
THIS ACTIVITY IS EXPECTED TO AFFECT THE TRI-CITIES AND THUMB REGION
LATE THIS AFTERNOON AND EARLY EVENING...BRINGING ONLY A THREAT FOR
ISOLATED SHOWERS. MODELS HAVE BEEN VERY CONSISTENT WITH WEAKENING
THE LOW-LEVEL THERMAL TROUGH ASSOCIATED WITH THIS FEATURE AS IT
CROSSES THE STATE...AND WILL THEREFORE KEEP CHANCES FOR RAIN OUT OF
THE THUMB THIS EVENING.

SIGNIFICANT CHANGE WAS MADE TO THE OVERNIGHT FORECAST AS THE STRONG
SHORTWAVE TROUGH CURRENTLY OVER CENTRAL NEBRASKA IS NOW FORECAST TO
LIFT NORTHEAST AND THROUGH LOWER MICHIGAN LATE TONIGHT AND EARLY
TOMORROW. SO FAR IN THE CENTRAL PLAINS TODAY...THIS SHORTWAVE HAS
BEEN GENERATING SHOWERS AHEAD OF AND JUST SOUTH OF IT AS THE
DISTURBANCE RIDES ALONG AN H850-700 BAROCLINIC ZONE WHICH STRETCHES
FROM KANSAS/NEBRASKA UP INTO THE SOUTHERN GREAT LAKES. ALTHOUGH ONLY
A MODEST INCREASE IN MOISTURE IS EXPECTED LATE TONIGHT...LIFT WILL
BE ENHANCED BY SOME LEFT EXIT REGION DYNAMICS...AND HELP TO MAKE
THE BEST OF AVAILABLE MOISTURE. EXPECT TO SEE PRECIPITATION FROM
THIS SYSTEM SPREAD INTO SOUTHEAST MICHIGAN VERY LATE TONIGHT AND
CONTINUE TO FUNNEL IN THROUGH THE OVERNIGHT HOURS. WITH THE EXPECTED
INCREASE IN CLOUD COVER AND PRECIPITATION...HAD TO BUMP FORECAST
MINS UP A FEW DEGREES...BUT READINGS ARE STILL EXPECTED TO BE IN THE
50S.

&&

.LONG TERM...SUNDAY THROUGH NEXT SATURDAY

MOISTURE LADEN AIRMASS WILL LINGER ACROSS THE FORECAST AREA SUNDAY
MORNING.  THE COMBINATION OF ADEQUATE MOISTURE TRANSPORT AND
MID-LEVEL /850-600MB/ FGEN WILL SUPPORT CONTINUED SHOWER
DEVELOPMENT.  BOTH THE GFS AND NAM ARE ADVERTISING SOME WEAK
ELEVATED INSTABILITY...ENOUGH TO SUPPORT A MENTIONABLE CHANCE FOR
THUNDER AS THE STRONGEST DYNAMICS SWING THROUGH.  MID-LEVEL HEIGHTS
WILL BUILD QUICKLY...SUPPORTING DEEP LAYER SUBSIDENCE LATER IN THE
DAY.   THIS SHOULD HELP SCOUR THE CLOUDS OUT SUBSTANTIALLY...IN
SPITE OF SOME SIGNS OF RESIDUAL MOISTURE BELOW 700MB.  THEREFORE...
EXPECT TEMPS TO RECOVER INTO THE LOW-MID 70S.

NWP SOLUTIONS ARE TRENDING TOWARD CONTRACTING THE WAVELENGTH OF THE
NEXT SHORTWAVE AS IT APPROACHES THE LAKES REGION LATE MONDAY -
RESULTING IN MORE AMPLIFICATION. THE NCEP PROGS ARE CERTAINLY
FAVORING GREATER DEVELOPMENT - THE GFS BEING THE STRONGEST -
COMPARED TO THE IMPORTED SOLUTIONS. HOWEVER...THE NEW ECMWF IS ALSO
TRENDING STRONGER - THOUGH STILL TEMPERED COMPARED TO THE GFS/NAM
DEPICTIONS.  FURTHERMORE...THE VAST MAJORITY OF THE 12Z GEFS MEMBERS
ARE FAVORING A SOLUTION THAT IS MUCH MORE AMPLIFIED.  EXPECT THE
STRONGER SOLUTION TO RESULT IN A SLIGHTLY SLOWER PROGRESSION OF THE
KEY PLAYERS. THEREFORE...WILL RETARD THE ONSET OF PRECIP CHANCES TO
LATE ON MONDAY...WITH THE BEST OPPORTUNITY MONDAY NIGHT LINGERING
INTO TUESDAY MORNING. GREATER DEVELOPMENT OF THE WAVE ALSO OPENS THE
DOOR TO ADVECT AN AIRMASS WITH MORE INSTABILITY INTO THE FORECAST
AREA AS WELL - THUS WILL INTRODUCE THUNDER TO THE FORECAST.

THE LARGE SCALE FLOW REGIME WILL REMAIN QUITE PROGRESSIVE THROUGH
THE REMAINDER OF THE WEEK...WHICH WILL KEEP HIGHS QUITE SEASONABLE.
THE NEXT DISCERNIBLE SHORTWAVE IS EXPECTED TO AFFECT THE REGION
THURSDAY AND FRIDAY.

&&

.MARINE...

SOUTHWESTERLY WINDS WILL BE ON THE INCREASE SUNDAY AS A SURFACE
TROUGH MOVES THROUGH THE REGION.  THIS WILL SET THE STAGE FOR HIGHER
WAVES ON SAGINAW BAY - BUT NOT EXPECTING CONDITIONS TO DETERIORATE
TO ADVISORY CRITERIA.  A LOW PRESSURE IS PROJECTED TO TRAVERSE THE
LAKES REGION ON TUESDAY AND IS EXPECTED TO STRENGTHEN DURING THAT
TIME.  AS A RESULT NORTHWESTERLY GALE FORCE WINDS ARE POSSIBLE
TUESDAY AND TUESDAY NIGHT ACROSS LAKE HURON AS THE LOW DEPARTS THE
REGION.  WINDS AND WAVES SHOULD SUBSIDE RATHER QUICKLY BY LATE
WEDNESDAY AS HIGH PRESSURE BUILDS BACK INTO THE REGION.

&&

.PREV DISCUSSION...ISSUED 150 PM EDT SAT SEP 6 2008

AVIATION...

OVERNIGHT FORECAST HAS CHANGED SIGNIFICANTLY AS AN UPPER LEVEL
DISTURBANCE NOW KICKING OFF AN EXPANSIVE AREA OF SHOWERS OVER THE
CENTRAL PLAINS IS NOW EXPECTED TO TRACK UP INTO SOUTHERN LOWER
MICHIGAN LATE TONIGHT AND TOMORROW MORNING. CHANCES FOR RAIN ARE
NOW PRETTY GOOD...AND HAVE ADDED SHRA AND LOWERED CEILINGS/VIS AT ALL
TAF SITES STARTING EARLY TOMORROW MORNING. RADAR IMAGERY FROM THE
PLAINS SUGGESTS OUR FORECAST MODELS ARE A LITTLE OVERDONE WITH THE
COVERAGE AND RAINFALL AMOUNTS...AND WILL LEAN TOWARDS A LESS
AGRESSIVE FORECAST FOR CEILINGS AND VISIBILITIES. FORECAST COULD
NEED TO BE RAMPED UP WITH LATER ISSUANCES HOWEVER. CURRENT
FORECAST CALLS FOR MVFR CONDITIONS TOWARDS DAYBREAK THROUGH EARLY
AFTERNOON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...HLO
LONG TERM....MANN
MARINE.......MANN
AVIATION.....HLO


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

000
FXUS63 KAPX 061950
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
350 PM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 348 PM/

A WEAK LOW PRESSURE SYSTEM WILL MOVE OVER LAKE SUPERIOR
TONIGHT BEFORE EXITING INTO ONTARIO TOMORROW. THIS FEATURE
WILL GENERATE A FEW LIGHT RAIN SHOWERS...OVER NORTHERN MICHIGAN
THROUGH TONIGHT.

A SECOND STORM SYSTEM...MOVING OVER CENTRAL CANADA AND THE
UPPER MIDWEST...WILL SWING OVER THE GREAT LAKES SUNDAY NIGHT.
THIS SYSTEM IS EXPECTED TO GENERATE ANOTHER ROUND OF SHOWERS...
OVER THE NORTHERN LAKES SUNDAY NIGHT AND MONDAY.

&&

.SHORT TERM.../ISSUED AT 348 PM/...THIS EVENING AND TONIGHT

LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW WEAK LOW
PRESSURE CENTERED NEAR MQT WITH AN EQUALLY AS WEAK SURFACE
TROUGH/CONVERGENCE AXIS BISECTING THE FORECAST AREA FROM NORTH TO
SOUTH.  WITHIN A LOOSE LOW LEVEL THETAE AXIS AHEAD OF THE
TROUGH...DIURNAL HEATING HAS CONTRIBUTED TO SPOTTY SHOWER
ACTIVITY...MOST PREVALENT ACROSS EASTERN UPPER AND THE FAR NORTHERN
LOWER LAKE HURON SHORELINE.  THE WARM WATERS OF THE NORTHERN GREAT
LAKES HAVE GIVEN A BOOST TO THESE SHOWERS AS DELTA T/S ARE AROUND
11C.  WITH THE LOCAL CONVERGENCE ALONG THE TROUGH AND OVER-WATER
INSTABILITY...A COUPLE WATERSPOUTS HAVE BEEN SIGHTED NEAR THE
STRAITS AND NORTHERN LAKE HURON SHORELINE.  AN ADDITIONAL TROUGH
EXTENDS WEST FROM THE SURFACE LOW TOWARDS NORTHERN WISCONSIN...WHICH
IS ALSO SUPPORTING SHOWER ACTIVITY.  FARTHER SOUTHWEST...A FAIRLY
POTENT WAVE IS MOVING ACROSS NEBRASKA/IOWA WHICH HAS EYES ON THE
SOUTHERN GREAT LAKES.  PRECIP CHANCES ARE THE MAIN FORECAST CONCERNS
TONIGHT.

TONIGHT...WEAK SURFACE LOW OVER THE NORTH-CENTRAL U.P. WILL SHIFT NE
ACROSS LAKE SUPERIOR.  LOOSELY DEFINED LOW LEVEL THETAE AXIS
EMANATING FROM THIS LOW WILL EXIT INTO LAKE HURON BY
MID-EVENING...ENDING ANY SPOTTY SHOWER AND WATERSPOUT THREAT ACROSS
NORTHERN LOWER FOR A PERIOD.  THINGS NOT QUITE AS CLEAR ACROSS
EASTERN UPPER WHERE LOW LEVEL CONVERGENCE IS A LITTLE BETTER AS A
RESULT OF THE SURFACE LOW NEARBY.  THERE MAY VERY WELL BE A BREAK IN
THE ACTION ACROSS EASTERN UPPER DURING THE EVENING AS WELL...AS
MID-LEVEL DRY AIR AND ISENTROPIC DESCENT ARRIVE FOR A LITTLE WHILE.
NAM/GFS BOTH POINT TOWARDS A SECONDARY TROUGH DROPPING SE ACROSS
NORTHERN LAKE MICHIGAN AND EASTERN UPPER AFTER MIDNIGHT.  IF THIS
MORNING WAS ANY INDICATION...INSTABILITY GENERATED BY DELTA T/S
AROUND 11C OVER NORTHERN LAKE MICHIGAN MAY PROVIDE A BOOST TO ANY
SHOWERS THAT DO DEVELOP ALONG THE TROUGH.  OTHERWISE...DECENT
LOOKING SHORTWAVE OVER NEBRASKA WILL MOVE INTO THE SOUTHERN GREAT
LAKES BY MORNING.  MID AND HIGH CLOUDS WILL SPREAD ACROSS NORTHERN
MICHIGAN AHEAD OF THIS SYSTEM DURING THE EVENING AND OVERNIGHT.
DEEPEST MOISTURE FROM THIS SYSTEM WILL REMAIN TO THE SOUTH BUT
PROBABLY CLOSE ENOUGH TO WARRANT AN ISOLATED SHOWER ALONG AND SOUTH
OF M-55 VERY LATE.  LOWS IN THE MID 40S TO LOW 50S.

MPC

&&

.LONG TERM.../ISSUED AT 348 PM/...TONIGHT AND BEYOND

INTERESTINGLY...TURN THE SWITCH TO METEOROLOGICAL FALL
AND THE WEATHER PATTERN SEEMS TO FOLLOW SUIT...FEATURING A MUCH MORE
ACTIVE NORTHERN STREAM FLOW OVER THE NORTHERN CONUS. THIS PATTERN IS
EXPECTED TO CONTINUE FOR THE FORESEEABLE FUTURE...FEATURING BROAD
NORTHERN CONUS AND WESTERN LAKES MID LEVEL TROUGHINESS...WHICH WILL
BE RIDDLED WITH RELATIVELY FAST MOVING...HARD TO TIME SHORTWAVES.
ALTHOUGH MUCH UNCERTAINTY PLAGUES THE EXTENDED...SOME USEFUL
INFORMATION CAN BE ASCERTAINED...NAMELY A CONTINUATION OF THE
RELATIVELY WET PATTERN AND MAINTENANCE OF THE COOL EARLY SEPTEMBER
TEMPERATURES.

ALTHOUGH FORECAST CONFIDENCE REGARDING SPECIFIC SHORTWAVE TIMING
DECREASES NEARLY EXPONENTIALLY FARTHER OUT IN THE EXTENDED...
CONFIDENCE SOMEWHAT HIGHER (ALTHOUGH STILL NOT AS HIGH AS ONE WOULD
LIKE) THROUGH MONDAY NIGHT AS NOAM WATER VAPOR ANALYSIS CONFIRMS
LATEST MODEL GUIDANCE THAT TRIFECTA OF DECENT SHORTWAVES WILL AFFECT
THE GREAT LAKES...ONE EXITING STAGE RIGHT DURING SUNDAY MORNING...
WITH PROGRESSIVELY STRONGER ONES CUTTING THROUGH THE REGION SUNDAY
NIGHT AND MONDAY NIGHT. ALTHOUGH MOISTURE PROFILES NOT OVERWHELMING
THROUGH THIS PERIOD...DYNAMICS SHOULD MORE THAN COMPENSATE...
BRINGING PERIODIC RAIN CHANCES...ESPECIALLY DURING PASSAGE OF
AFOREMENTIONED WAVES. STILL LOOKING LIKE BETTER DYNAMICS WITH
SUNDAYS WAVE WILL PASS SOUTH OF THE REGION...AND HAVE CONTINUED TO
FOCUS BETTER POTENTIAL IN OUR SOUTHERN ZONES (STILL LOW CHANCE AT
BEST). INTERESTINGLY...FARTHER NORTH...PASSAGE OF SUBTLE SURFACE
TROUGH OVER LAKE MICHIGAN DURING THE MORNING...AUGMENTED WITH
POSSIBLE LAND BREEZE CONVERGENCE AXIS...MOISTURE FLUX FROM THE
RELATIVELY WARM LAKE WATERS (DELTA T/S ON THE ORDER OF 11C TO
12C)...AND MID LEVEL WEAK SHEAR AXIS MAY BE ENOUGH TO KICK OFF A
SCATTERED LINE OF SHOWERS OVER THE WATER TOWARDS MORNING...WHICH
PROPAGATE INLAND AS SYNOPTIC WIND REGIME OVERWHELMS THE LAND BREEZE.
A SIMILAR SCENARIO UNFOLDED THIS PAST MORNING...WITH CLEAR EVIDENCE
OF ADDED LAKE MICHIGAN SUPPORT AS SHOWERS ADVANCED FROM WISCONSIN.
OTHERWISE...HAVE REMOVED POPS FOR THE AFTERNOON HOURS WITH SOME
SEMBLANCE OF LOW AMPLITUDE RIDGE AXIS PIVOTING INTO THE AREA. NEXT
WAVE SLATED TO DROP SOUTHEAST SUNDAY NIGHT...THIS TIME WITH BETTER
DYNAMICS PASSING OVER EASTERN UPPER MICHIGAN AND POINTS NORTH. MUCH
LIKE SUNDAY...JUST NOT OVERLY SOLD ON SHOWER POTENTIAL WITH LIMITED
MOISTURE PROFILES AND BETTER MID LEVEL SUPPORT ESSENTIALLY PASSING
NORTH OF THE AREA. WILL TAPER CHANCE POPS FROM NORTH TO SOUTH...WITH
SOME WEST/EAST TIMING. WILL KEEP SLIGHT CHANCE THUNDER MENTION WITH
900MB LIFTED PARCELS YIELDING NEARLY 400 J/KG MEAN LAYER CAPE.

PROBABLY THE MOST INTERESTING WEATHER OF THE EXTENDED BEGINS LATE
MONDAY NIGHT...CONTINUING THROUGH TUESDAY MORNING...AS STRONG
SHORTWAVE MAKES THE TURN TO THE EAST NORTHEAST OVER THE CENTRAL
PLAINS...WITH SIGHTS SET ON THE GREAT LAKES REGION. LATEST NAM-WRF
AND GFS GUIDANCE HAVE REALLY AMPLIFIED THIS SYSTEM...DROPPING
SURFACE PRESSURE TO SUB 1000MB AS IT PASSES THROUGH NORTHERN
MICHIGAN. OTHER GUIDANCE REMAINS MUCH LESS AGGRESSIVE...AND HENCE
FARTHER SOUTHEAST WITH THE SURFACE LOW (IN FACT...12Z GEM HAS
ESSENTIALLY NO SURFACE REFLECTION). IF AMERICAN GUIDANCE IS TO BE
BELIEVED...RAIN...LOCALLY HEAVY (OVER AN INCH WITH QPF FIELDS) WILL
QUICKLY OVERSPREAD THE AREA LATE MONDAY AFTERNOON...CONTINUING
THROUGH MONDAY NIGHT. LOOKING AT MID LEVEL HEIGHT FIELDS...IT
APPEARS BOTH THE NAM-WRF AND GFS ARE UNREALISTICALLY AGGRESSIVE
WITH DOWNSTREAM RIDGE RESPONSE (TOO QUICKLY BUILDING HEIGHTS) AFTER
PASSAGES OF LATE WEEKEND SHORTWAVES. THIS ALLOWS UPSTREAM SHORTWAVE
TO OVER-AMPLIFY AND PUSH FARTHER NORTHEAST. IN LIGHT OF THE
ABOVE...WILL SIDE WITH THE MORE CONSERVATIVE GUIDANCE...FEATURING
LIKELY POPS OVER THE SOUTH HALF OF THE AREA AND MUCH LESS RAINFALL.
HAVE LINGERED LIGHT SHOWER MENTION INTO TUESDAY MORNING AS SYSTEM
PULLS OFF TO THE EAST AND WEAK NORTHWEST FLOW LAKE EFFECT RAIN
SHOWERS POSSIBLY DEVELOP AS 850MB TEMPERATURES DROP TO THE SINGLE
DIGITS.

LOOKING FARTHER OUT...AS MENTIONED...QUESTIONS ABOUND LATER IN THE
FORECAST PERIOD. IN GENERAL...STILL LIKE THE IDEA OF A DRY MIDWEEK
PERIOD AS SURFACE AND MID LEVEL RIDGE AXES CREST THE REGION. BEYOND
THIS...MODELS HINTING AT ANOTHER FAIRLY STRONG SHORTWAVE PASSING
THROUGH LATE IN THE WEEK...BRINGING ANOTHER CHANCE OF SHOWERS.
HOWEVER...WITH HURRICANE IKE NOW SLATED TO PASS INTO THE GULF OF
MEXICO (PER LATEST NHC GUIDANCE)...WOULD EXPECT THIS FEATURE TO AT
LEAST TRY TO FLEX ITS MUSCLE ON OVERALL CONUS FLOW REGIME...POSSIBLY
PLAYING SOME HAVOC ON AMPLITUDE AND TIMING OF THE NORTHERN STREAM
SHORTWAVE. GIVEN UNCERTAINTIES...FELT IT WOULD BE A FORECAST
INJUSTICE TO TRY ANY SORT OF TIMING...AND HAVE TOOK THE SIMPLE
APPROACH OF MAINTAINING FORECAST CONTINUITY WITH POP AND WEATHER
GRIDS AND RUNNING WITH HPC GUIDANCE ALL OTHERS.

TEMPERATURES THROUGH THE EXTENDED WILL REMAIN NEAR TO SLIGHTLY BELOW
SEASONAL NORMALS...WITH HIGHS IN THE 60S TO LOW 70S AND OVERNIGHT
LOWS GENERALLY IN THE 40S AND 50S.

MSB


&&

.MARINE.../ISSUED AT 348 PM/

SHOWERS AND ISOLATED WATERSPOUTS CONTINUE TO FORM ALONG A
SURFACE CONVERGENCE AXIS...AND HAVE BEEN GETTING A BOOST FROM THE
WARM LAKE WATERS OF THE NORTHERN GREAT LAKES.  SHOWER...ALONG WITH
THE THREAT OF WATERSPOUTS...WILL BE POSSIBLE ALONG THIS AXIS ACROSS
NE LOWER AND FAR EASTERN UPPER UNTIL THIS AXIS MOVES OVER THE OPEN
WATERS OF LAKE HURON THIS EVENING.  OTHERWISE...NO OTHER MARINE
HAZARDS ARE EXPECTED SINCE WINDS WILL REMAIN LIGHT TONIGHT.

MPC

&&

.AVIATION.../ISSUED AT 100 PM/...VALID FOR 18Z TAFS

CHALLENGING FORECAST OVER THE NEXT 24 HOURS.  WEAK
SURFACE LOW OVER CENTRAL UPPER MICHIGAN WILL TRACK NE OVER LAKE
SUPERIOR WITH ITS TRAILING COOL FRONT/SURFACE TROUGH CROSSING
NORTHERN LOWER THROUGH THE AFTERNOON.  SHOWERS WILL REMAIN SPOTTY
WITH LIMITED CHANCES OF IMPACT ON THE TAF SITES.  SECONDARY SURFACE
TROUGH WILL PASS ACROSS THE AREA EARLY TOMORROW MORNING.  HARD TO
SAY IF ANY LOW CLOUDS/FOG WILL ACCOMPANY THIS TROUGH.  CERTAINLY IS
POSSIBLE...JUDGING BY WHAT OCCURRED UPSTREAM THIS MORNING.  BEST
CHANCES WOULD APPEAR TO BE AT PLN AND WILL TREND TOWARDS LOWER VSBYS
AND CIGS...BUT WILL REFRAIN FROM GOING LOCK/STOCK/AND BARREL DUE TO
POOR MODEL GUIDANCE. SO...WILL KEEP VFR GOING THROUGH THE TAF PERIOD
EXCEPT AT PLN.

MPC

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KDTX 061750
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
150 PM EDT SAT SEP 6 2008


.AVIATION...

OVERNIGHT FORECAST HAS CHANGED SIGNIFICANTLY AS AN UPPER LEVEL
DISTURBANCE NOW KICKING OFF AN EXPANSIVE AREA OF SHOWERS OVER THE
CENTRAL PLAINS IS NOW EXPECTED TO TRACK UP INTO SOUTHERN LOWER
MICHIGAN LATE TONIGHT AND TOMORROW MORNING. CHANCES FOR RAIN ARE
NOW PRETTY GOOD...AND HAVE ADDED SHRA AND LOWERED CEILINGS/VIS AT ALL
TAF SITES STARTING EARLY TOMORROW MORNING. RADAR IMAGERY FROM THE
PLAINS SUGGESTS OUR FORECAST MODELS ARE A LITTLE OVERDONE WITH THE
COVERAGE AND RAINFALL AMOUNTS...AND WILL LEAN TOWARDS A LESS
AGRESSIVE FORECAST FOR CEILINGS AND VISIBILITIES. FORECAST COULD
NEED TO BE RAMPED UP WITH LATER ISSUANCES HOWEVER. CURRENT
FORECAST CALLS FOR MVFR CONDITIONS TOWARDS DAYBREAK THROUGH EARLY
AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 330 AM EDT SAT SEP 6 2008

SHORT TERM...TODAY

BROAD UPPER LEVEL TROUGHING NOW ENCOMPASSING MUCH OF THE CENTRAL
CONUS WILL ALLOW SEVERAL WEAKER SHORTWAVES TO TRANSLATE
EAST-NORTHEAST WITHIN THE MEAN FLOW OVER THE COMING DAYS.  LATEST
WATER VAPOR IMAGERY SHOWS THE FIRST OF THESE IMPULSES SHEARING
NORTHEAST INTO SOUTHWEST WI...WHILE A SECOND WAVE PUSHES TOWARD
WESTERN IA.   MEANWHILE...BROAD AREA OF HIGH PRESSURE CENTERED OVER
THE CENTRAL PLAINS BEGINNING TO EXTEND NORTHEAST INTO SOUTHEAST
LOWER MI.  STUBBORN LOW STRATUS HANGING ON LOCALLY BENEATH A STRONG
INVERSION...ALTHOUGH SATELLITE TRENDS INDICATING A FEW MORE BREAKS
DEVELOPING WITHIN THIS DECK ESPECIALLY WEST OF I-75.

WEAK HIGH PRESSURE WILL REMAIN THE PREDOMINANT LARGE SCALE FEATURE
ACROSS SOUTHEAST LOWER MI TODAY.  ALTHOUGH THE MODEL MOISTURE FIELDS
ARE SHOWING SOME DIFFICULTY IN HANDLING THE CURRENT STRATUS
DECK...WOULD EXPECT EVENTUAL SCATTERING/LIFTING OF ANY LINGERING
STRATUS BY LATE MORNING AS THE LOW LEVEL THERMAL TROUGH PUSHES
EAST.  WEAK SHORTWAVE SHEARING NORTHEAST FROM IOWA TO CENTRAL LOWER
MI MAY BRING SOME ADDITIONAL MID LEVEL CLOUDINESS BY LATE
AFTERNOON.   ALTHOUGH THERE REMAINS A LACK OF GOOD FORCING OR
MOISTURE ADVECTION ASSOCIATED WITH THIS SYSTEM...CANNOT RULE OUT A
LIGHT SHOWER/ SPRINKLES ACROSS MIDLAND/BAY COUNTIES AS A WEAK SFC
TROUGH LIFTS THROUGH.

AIRMASS WILL MODERATE SLIGHTLY FROM YESTERDAY...AIDED BY A FAIR
AMOUNT OF INSOLATION.  THIS WILL MAINTAIN HIGHS AROUND NORMAL IN THE
LOW/MID 70S.

LONG TERM...

NEAR NORMAL TEMPERATURES LOOK TO GIVE WAY TO BELOW NORMAL TEMPS
BY MIDWEEK...ALONG WITH AN INCREASING CHANCE OF RAIN THROUGH
MONDAY NIGHT.

RATHER AMPLIFIED UPPER LEVEL TROUGH OVER THE ROCKIES/CENTRAL CONUS
WILL TRANSITION TO A BIT MORE ZONAL FLOW OVER THE NORTHERN
CONUS...BEFORE SHARPENING TROUGH AXIS TRACKS THROUGH THE GREAT LAKES
REGION BY MID WEEK. SEVERAL CHANCES FOR RAIN WITH NUMEROUS
SHORTWAVES TRAVELING WITHIN THE JET STREAM. BEST CHANCE OF RAIN
APPEARS TO BE LATE MONDAY/MONDAY NIGHT...WITH VERY TIGHT BAROCLINIC
ZONE SETTING UP OVER THE SOUTHERN GREAT LAKES AND RAPID CYCLOGENESIS
TAKING PLACE...PER 00Z GFS/EUROPEAN/CANADIAN GLOBAL...WITH GOOD
ISENTROPIC ASCENT PROGGED. SIGNIFICANT LOW LEVEL COLD ADVECTION IN
THE LOWS WAKE TUESDAY MORNING...AS 850 MB TEMPS FORECASTED TO FALL
INTO THE MID SINGLE NUMBERS...LIKELY HOLDING MAX TEMPS IN THE UPPER
60S TO AROUND 70 DEGREES. THIS SHOULD SET UP A VERY COOL NIGHT
TUESDAY NIGHT AS HIGH PRESSURE BUILDS INTO SOUTHEAST
MICHIGAN...ALLOWING TEMPS TO DROP INTO THE 40S. OTHERWISE...LOOKING
FOR NEAR NORMAL TEMPS (IN LINE WITH MAV GUIDANCE) DURING THE NEXT
COUPLE OF DAYS.

MARINE...

HIGH PRESSURE NOSING NORTHEAST INTO THE CENTRAL GREAT LAKES ALLOWING
WINDS TO WEAKEN OVERNIGHT...LEADING TO A REDUCTION IN WAVE HEIGHTS.
THUS...THE REMAINING SMALL CRAFT ADVISORIES WILL BE DROPPED EARLY
THIS MORNING.  OTHERWISE...FAVORABLE BOATING CONDITIONS WILL EXIST
THROUGH THE DURATION OF THE WEEKEND AS HIGH PRESSURE EXPANDS EAST
ACROSS THE REGION.  ANOTHER LOW PRESSURE SYSTEM WILL BRING THE NEXT
COLD FRONT THROUGH THE REGION ON MONDAY...POTENTIALLY CREATING MORE
UNSTABLE CONDITIONS BY MONDAY NIGHT AND TUESDAY AS MUCH COOLER AIR
FILTERS ACROSS THE WARMER LAKE WATERS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....HLO
SHORT TERM...MR
LONG TERM....SF
MARINE.......MR


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

000
FXUS63 KGRR 061730
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
131 PM EDT SAT SEP 6 2008

LATEST UPDATE...AVIATION...

.SYNOPSIS...(330 AM EDT SAT SEP 6 2008)
AN UPPER LEVEL TROUGH ACROSS THE MID SECTION OF THE NATION WILL
RESULT IN A SOMEWHAT UNSETTLED WEATHER PATTERN THROUGH EARLY NEXT
WEEK. SEVERAL UPPER LEVEL DISTURBANCES WILL LEAD TO SEVERAL CHANCES
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. HOWEVER DRY
CONDITIONS WILL PREVAIL THE MAJORITY OF THE TIME THIS WEEKEND AND
OUR BEST CHANCE FOR PRECIPITATION SHOULD HOLD OFF UNTIL LATE MONDAY.

&&

.SHORT TERM...(1150 AM EDT SAT SEP 6 2008)
(TODAY THROUGH MONDAY AFTERNOON)
HAD TO EXPAND POPS SLIGHTLY FARTHER SOUTH IN AN EARLIER AMENDMENT TO
ACCOUNT FOR THE SHOWERS CURRENTLY MOVING INTO THE GRAND HAVEN AND
FERRYSBURG AREAS. POPS ARE NOW IN THE GRIDS NORTH OF A LINE FROM
ROUGHLY SOUTH HAVEN TO GRAND RAPIDS TO ALMA.

WEAK N-S ORIENTED SFC TROUGH OVER LAKE MICH (LIKELY ENHANCED BY
MORNING LAND BREEZE) HAS BEEN GENERATING A FEW ISOLATED SHOWERS THIS
MORNING BETWEEN GRAND HAVEN AND LUDINGTON. AS THIS FEATURE PUSHES TO
THE EAST... A MORE UNIFORM WEST SOUTHWEST WIND FLOW SHOULD DEVELOP
OVER THE LAKE. THIS OUGHT TO END THE SHOWER THREAT AT THE LAKESHORE
BY 18Z AND THE BETTER SFC CONVERGENCE SHOULD BE FOCUSED INLAND AFTER
18Z.


PVA ACROSS OUR ENTIRE CWFA LOOKS FAIRLY IMPRESSIVE TONIGHT.
THEREFORE WE WILL CONTINUE TO MENTION A SLIGHT CHC FOR SHOWERS
ACROSS OUR CWFA... ESPECIALLY AFTER REVIEWING 00Z GFS GUIDANCE.

GIVEN THE UPPER LEVEL PATTERN SUNDAY INTO EARLY NEXT WEEK... WE WILL
NEED TO CONTINUE TO CARRY POPS THROUGH MONDAY AFTERNOON. IT STILL
APPEARS THAT POPS WILL INCREASE GRADUALLY... PARTICULARLY LATE
MONDAY AS THE PRIMARY SHORTWAVE MOVES IN. HOWEVER TIMING SHORTWAVES
IN THIS TYPE PATTERN IS TRICKY... AND POPS WILL REMAIN NECESSARY
SUNDAY THROUGH MONDAY.

IT SHOULD BE STRESSED THAT DRY CONDITIONS WILL PREVAIL THE MAJORITY
OF THE TIME THIS WEEKEND. OUR BEST CHC FOR RAIN SHOULD HOLD OFF
UNTIL LATE MONDAY.

&&

.LONG TERM...(330 AM EDT SAT SEP 6 2008)
(MONDAY NIGHT THROUGH FRIDAY)

NO SIGNIFICANT CHANGES TO THE EXTENDED PERIOD. THERE IS GENERALLY
GOOD MODEL AGREEMENT ON EVOLUTION OF A SHORTWAVE TROUGH EARLY IN THE
WEEK. WILL KEEP CHANCE POPS MONDAY NIGHT WITH DEEPER MOISTURE AND
PRECIP DEPARTING TO THE EAST BY 12Z TUESDAY. SFC HIGH BUILDS IN WITH
FAIR WEATHER FOR TUESDAY AND WEDNESDAY. DROPPED POPS FOR WEDNESDAY
NIGHT AS IT APPEARS RETURN MOISTURE AND OVERRUNNING SHOWERS WILL NOT
ARRIVE UNTIL AFTER 12Z THURSDAY. LOOKS LIKE A WIDESPREAD RAIN EVENT
FOR THURSDAY OR FRIDAY AS SHORTWAVE TROUGH AND SFC LOW ARRIVE WITH
TRAILING COLD FRONT PUSHING THROUGH BY THE END OF THE EXTENDED
PERIOD.

&&

.MARINE...(1150 AM EDT SAT SEP 6 2008)
THE POSSIBILITY OF WATERSPOUTS WAS DISCUSSED THIS MORNING AS THE
CUMULUS OVER THE LAKE ON VIS SATELLITE HAD A SIMILAR APPEARANCE TO
THE EVENT ABOUT A MONTH AGO. HOWEVER LIMITING FACTORS ARE THAT LK MI
SFC WATERS TEMPS ARE IN THE MID 40S TO MID 50S IN THE VICINITY OF
THE SHOWERS AND THE DEPTH OF THE CONVECTIVE LAYER IS RELATIVELY
SHALLOW.

&&

.AVIATION...(131 PM EDT SAT SEP 6 2008)
SHOWERS WILL DIMINISH ACROSS THE NRN CWA THIS AFTERNOON. MUCH OF THE
CWA WILL SEE SCT CU THIS AFTERNOON. AN UPPER LOW WILL MOVE ACROSS
THE REGION LATE TONIGHT AND EARLY SUNDAY. THIS MAY GENERATE SHOWERS
ACROSS THE CWA. TAF SITES SHOULD REMAIN VFR.

&&

.HYDROLOGY...(330 AM EDT SAT SEP 6 2008)
RAINFALL AMOUNTS THIS WEEKEND WILL AVERAGE BELOW ONE HALF INCH AND
RAIN WILL BE SCATTERED IN COVERAGE. THIS SHOULD HAVE LITTLE TO NO
IMPACT ON THE CURRENT HYDRO SITUATION.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.

&&

$$

SYNOPSIS:     LAURENS
SHORT TERM:   LAURENS/MEADE
LONG TERM:    OSTUNO
MARINE:       MEADE
AVIATION:     93
HYDROLOGY:    LAURENS

000
FXUS63 KMQT 061730 AAB
AFDMQT

AREA FORECAST DISCUSSION...UPDATED FOR 18Z TAF ISSUANCE
NATIONAL WEATHER SERVICE MARQUETTE MI
130 PM EDT SAT SEP 6 2008

UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE

.DISCUSSION...
UPPER AIR PATTERN CONSISTS OF A 500 MB RIDGE OFF THE EAST COAST AND
WEST COASTS AND A LONGWAVE TROUGH ACROSS THE CENTRAL U.S. WITH
NUMEROUS SHORTWAVES EMBEDDED IN THE TROUGH. ON SHORTWAVE IS ACROSS
NORTHERN WI AND THIS HAS KICKED OFF SOME SHOWERS. THIS SHORTWAVE
MOVES THROUGH THIS MORNING AND THE TROUGH STAYS ACROSS THE AREA
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK.

NAM TAKING 850-500 MB Q-VECTOR CONVERGENCE AND SOME MOISTURE AND
MOVES THEM OUT TONIGHT BEFORE RETURNING THEM BOTH SUN EVENING AND
RETURNING BOTH AGAIN MON NIGHT. GFS SHOWS ABOUT THE SAME THING AND
WILL USE A BLEND OF THE ECMWF/GFS AND NAM FOR THIS FORECAST. LOOKS
UNSETTLED FOR A WHILE AND THERE WILL BE CHANCES OF RAIN THROUGH MOST
OF THIS WEEKEND...HOWEVER A WIDESPREAD AND HEAVY RAINFALL DOES NOT
LOOK LIKELY AT THIS TIME. OVERALL...DID NOT MAKE TOO MANY CHANGES TO
THE GOING FORECAST. DID REMOVE THUNDER THOUGH FROM THE FORECAST AS
INSTABILITY IS MARGINAL ENOUGH FOR IT AT THIS TIME. TEMPERATURES
LOOKED GOOD AND MADE VERY FEW CHANGES. ABUNDANT AND DEEP MOISTURE DO
NOT LOOK LIKELY EITHER...SO KEPT CHANCE POPS IN THERE.

&&

.AVIATION (FOR THE 18Z TAF ISSUANCE)...

EXPECT MVFR CIGS TO PERSIST AT LEAST OCCASIONALLY AT BOTH SITES THE
REST OF THIS AFTN WITH LINGERING LLVL MSTR SHOWN ON RECENT TAMDAR
SDNGS/SMALL SFC DWPT DEPRESSIONS IN THE PRESENCE OF DIURNAL HTG. BUT
THE TREND SHOULD BE FOR A GRDL IMPROVEMENT WITH THIS SFC HTG LIFTING
THE CIG BASE. MVFR CIGS WL LIKELY REDVLP AT CMX TNGT WITH EXPECTED
UPSLOPE WLY FLOW AND DIURNAL COOLING BEFORE THE ARRIVAL OF DRIER AIR
NOW IN WRN MN TENDS TO BREAK UP ANY LO CLD. SAW WL BE MORE SHELTERED
FM THIS FLOW...SO RADIATION FOG IS A POSSIBILITY THERE. THEN VFR
CONDITIONS WL BE THE RULE AFT ANY MRNG FOG BURNS OFF AT SAW ON SUN
THRU 18Z.

&&

.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...

LOW PRESSURE OVER NW WI WILL BE MOVING ACROSS LAKE SUPERIOR TODAY
AND TONIGHT. WINDS UP TO 20 KT ARE POSSIBLE TODAY...MAINLY AROUND
THE LOW OVER WEST AND CENTRAL LAKE SUPERIOR. HOWEVER...THERE COULD
BE A PERIOD TONIGHT OVER SOUTHERN LAKE SUPERIOR OF UP TO 25 KT WEST
WINDS ON THE SOUTH SIDE OF THE LOW. WINDS WILL DIMINISH BELOW 20 KT
FOR SUN AS THE NEXT TROUGH APPROACHES FROM THE NW. IN THE WAKE OF
THIS TROUGH FOR SUN NIGHT INTO MON MORNING...COLD AIR IS EXPECTED TO
FLOW IN...RESULTING IN A PERIOD OF NW 15 TO 25 KT...POSSIBLY EVEN 30
KT WINDS. THE STRONGEST WINDS SHOULD OCCUR ON NORTH CENTRAL AND
EASTERN LAKE SUPERIOR MON MORNING. EXPECT WINDS TO DIMINISH MON AFTN
WITH WIND SPEED BELOW 20 KT FOR AFTER MIDNIGHT MON NIGHT INTO TUE AS
A RIDGE OF HIGH PRESSURE MOVES ACROSS. SOUTHERLY WINDS WILL ATTEMPT
TO PICK UP TUE NIGHT AS THE RIDGE HEADS OFF TO THE EAST...BUT
THINKING IS THAT STRONGER WINDS...UP TO 25 KT WILL HOLD OFF UNTIL
WED EVENING. THAT IS WHEN A TROUGH OF LOW PRESSURE APPROACHES FROM
THE PLAINS.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

DISCUSSION...GJM
AVIATION...KC
MARINE...AJ

000
FXUS63 KAPX 061702
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
102 PM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 724 AM/

A WEAK UPPER MIDWEST STORM SYSTEM...WILL MOVE OVER UPPER MICHIGAN
TODAY...BEFORE QUICKLY EXITING INTO ONTARIO THIS EVENING. THIS
FEATURE WILL GENERATE A FEW LIGHT RAIN SHOWERS OVER NORTHERN
MICHIGAN THROUGH THE AFTERNOON. SWR

&&

.SHORT TERM.../ISSUED AT 1037 AM/...THIS AFTERNOON

WEAK SURFACE LOW OVER WESTERN UPPER MICHIGAN IS GETTING
LEFT BEHIND PARENT SHORTWAVE TROUGH LIFTING ACROSS SOUTHERN
ONTARIO.  AREA OF SCATTERED SHOWERS IS MOSTLY CONFINED TO EASTERN
UPPER MICHIGAN WHERE BETTER ISENTROPIC ASCENT ON THE 295-300K
SURFACES IS LOCATED.  FARTHER SOUTH...WEAK COOL FRONT/SURFACE TROUGH
IS EXTENDING OVER NORTHERN LAKE MICHIGAN AND SOUTH ALONG THE EASTERN
SHORE OF LAKE MICHIGAN TO SE WISCONSIN...AND IS KICKING OFF ISOLATED
SHOWERS/SPRINKLES FROM LEELANAU PENINSULA TO LAKE COUNTY.
AFOREMENTIONED WEAK SURFACE LOW WILL SLOWLY SHIFT TO THE NE TOWARDS
LAKE SUPERIOR DURING THE AFTERNOON WHILE ITS COOL FRONT/TROUGH WILL
SHIFT SLOWLY EAST.  EXPECT SCT SHOWER ACTIVITY OVER NORTHERN
PORTIONS OF THE FORECAST AREA TO EXIT/DIMINISH BY MID-AFTERNOON WHEN
AREA OF ISENTROPIC ASCENT LIFTS NE INTO ONTARIO.  THINK WE WILL
CONTINUE TO SEE ISOLATED LIGHT SHOWERS/SPRINKLES POP UP ALONG THE
COOL FRONT AS IT SHIFTS EAST INTO NORTH-CENTRAL AND NE LOWER WITH A
LOOSE LOW LEVEL THETAE AXIS IN PLACE. ADJUSTED POP GRIDS TO REFLECT
THESE TRENDS AS WELL AS SOME CLEARING OVER NW LOWER LATE IN THE
AFTERNOON AS DRIER MID-LEVEL AIR WORKS IN.  OTHERWISE...VERY FEW
CHANGES MADE ELSEWHERE.

MPC

&&

.LONG TERM.../ISSUED AT 330 AM/...TONIGHT ONWARD

MODELS STILL STRUGGLE RESOLVING THE INDIVIDUAL WAVES WITHIN THE
BROADER UPPER TROF OVER THE NORTH CENTRAL US. THEY DO HOWEVER AGREE
ON WHEN THE BEST FORCING FOR PRECIP WILL BE...SUNDAY NIGHT AND AGAIN
MONDAY NIGHT.

TONIGHT...A SOMEWHAT WEAK SHORTWAVE WILL QUICKLY LIFT ENE ACROSS FAR
NORTHERN LOWER MI IN THE EVENING. IN ITS WAKE...THE WEAK SURFACE LOW
IN CENTRAL UPPER MI WILL DRIFT EASTWARD AND EVENTUALLY FILL. THE
BEST CHANCE FOR ANY PRECIP WILL BE IN THE EVENING IN EASTERN
UPPER...ONCE AGAIN WHERE MID LEVEL FORCING AND LOW/MID LEVEL SW
FLOW/ISENTROPIC ASCENT MATCH UP. BOTH OF THESE FALL APART LATE
TONIGHT. WILL HAVE SCT SHOWERS NORTH OF THE BRIDGE IN THE EVENING/
EARLY OVERNIGHT...DIMINISHING TO ISOLATED BY DAWN. EXTREME NORTHERN
LOWER WILL HAVE ISOLATED SHRA EARLY ON...WITH LITTLE PRECIP SOUTH OF
M-68. MOSTLY CLOUDY NORTH...PARTLY CLOUDY SOUTH (WHERE SOME BOG FOG
IS AGAIN POSSIBLE). MIN TEMPS LOW/MID 50S COASTS TO MID 40S IN THE
INTERIOR COOL SPOTS.

SUNDAY...MAIN ACTION SHOULD BE TO OUR SOUTH. A PAIR OF REASONABLY
VIGOROUS SHORTWAVES WILL RACE ENE INTO FAR SOUTHERN LOWER MI. A
ILL-DEFINED E-W SURFACE BOUNDARY WILL RESULT...ALSO WELL DOWNSTATE.
DEEPER MOISTURE WILL EVENTUALLY GET DRAWN NORTHWARD INTO OUR
SOUTHERN ZONES LATE IN THE DAY. WILL HAVE ISOLATED SHOWERS IN THE
MORNING IN THE SOUTH...EXPANDING ACROSS THE AREA IN THE AFTERNOON
WITH CHANCY (30-40) POPS IN THE SOUTH. INSTABILITY IS STILL MEAGER
(UP TO 300J/KG MUCAPE)...AND WILL NOT MENTION THUNDER. MAX TEMPS A
COUPLE DEGREES WARMER THAN TODAY...UPPER 60S TO LOWER 70S.

SUNDAY NIGHT/MONDAY...BEST SHOT OF RAIN FOR THE EVENT THUS FAR LOOKS
TO BE SUNDAY NIGHT...AS VORT RIBBON LIFTS NORTH FROM DOWNSTATE. A
SURFACE COLD FRONT WILL ALSO MOVE THRU THE FORECAST AREA FROM THE
NW. AND NOT QUITE WILLING TO GO WITH LIKELY POPS JUST YET...BUT WILL
BOOST TO 50 ACROSS THE ENTIRE AREA SUNDAY NIGHT. MONDAY MAY SEE A
RELATIVE LULL...WITH MID LEVEL SUBSIDENCE FOR AT LEAST PART OF THE
DAY AS VORT RIBBON PULLS OUT. REDUCED POPS A SMIDGE TO THE 30-40
RANGE. LOW TEMPS MAINLY AROUND 50. COLD ADVECTION MONDAY WILL KEEP
HIGHS MAINLY IN THE 60S.

REST OF THE FORECAST...ONE LAST MID-LEVEL TROF IN THE EPISODE WILL
GO THRU MONDAY NIGHT...WITH A RESULTING INCREASE IN PRECIP CHANCES.
STILL LOOKS LIKE WE DRY OUT MID-WEEK...BEFORE RETURN FLOW GETS GOING
WED NIGHT. TUESDAY WILL BE COOL LIKE MONDAY...WITH SOME RECOVERY IN
TEMPS INTO WED.

JZ

&&

.MARINE.../ISSUED AT 330 AM/

NO MARINE HEADLINES. DISORGANIZED PATTERN WILL KEEP SURFACE WINDS
LIGHT UNTIL SUNDAY NIGHT...AHEAD OF A COLD FRONT APPROACHING FROM
THE NW.

JZ

&&

.AVIATION.../ISSUED AT 100 PM/...VALID FOR 18Z TAFS

CHALLENGING FORECAST OVER THE NEXT 24 HOURS.  WEAK
SURFACE LOW OVER CENTRAL UPPER MICHIGAN WILL TRACK NE OVER LAKE
SUPERIOR WITH ITS TRAILING COOL FRONT/SURFACE TROUGH CROSSING
NORTHERN LOWER THROUGH THE AFTERNOON.  SHOWERS WILL REMAIN SPOTTY
WITH LIMITED CHANCES OF IMPACT ON THE TAF SITES.  SECONDARY SURFACE
TROUGH WILL PASS ACROSS THE AREA EARLY TOMORROW MORNING.  HARD TO
SAY IF ANY LOW CLOUDS/FOG WILL ACCOMPANY THIS TROUGH.  CERTAINLY IS
POSSIBLE...JUDGING BY WHAT OCCURRED UPSTREAM THIS MORNING.  BEST
CHANCES WOULD APPEAR TO BE AT PLN AND WILL TREND TOWARDS LOWER VSBYS
AND CIGS...BUT WILL REFRAIN FROM GOING LOCK/STOCK/AND BARREL DUE TO
POOR MODEL GUIDANCE. SO...WILL KEEP VFR GOING THROUGH THE TAF PERIOD
EXCEPT AT PLN.

MPC

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KGRR 061554
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1150 AM EDT SAT SEP 6 2008

LATEST UPDATE...SHORT TERM AND MARINE...

.SYNOPSIS...(330 AM EDT SAT SEP 6 2008)
AN UPPER LEVEL TROUGH ACROSS THE MID SECTION OF THE NATION WILL
RESULT IN A SOMEWHAT UNSETTLED WEATHER PATTERN THROUGH EARLY NEXT
WEEK. SEVERAL UPPER LEVEL DISTURBANCES WILL LEAD TO SEVERAL CHANCES
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. HOWEVER DRY
CONDITIONS WILL PREVAIL THE MAJORITY OF THE TIME THIS WEEKEND AND
OUR BEST CHANCE FOR PRECIPITATION SHOULD HOLD OFF UNTIL LATE MONDAY.

&&

.SHORT TERM...(1150 AM EDT SAT SEP 6 2008)
(TODAY THROUGH MONDAY AFTERNOON)
HAD TO EXPAND POPS SLIGHTLY FARTHER SOUTH IN AN EARLIER AMENDMENT TO
ACCOUNT FOR THE SHOWERS CURRENTLY MOVING INTO THE GRAND HAVEN AND
FERRYSBURG AREAS. POPS ARE NOW IN THE GRIDS NORTH OF A LINE FROM
ROUGHLY SOUTH HAVEN TO GRAND RAPIDS TO ALMA.

WEAK N-S ORIENTED SFC TROUGH OVER LAKE MICH (LIKELY ENHANCED BY
MORNING LAND BREEZE) HAS BEEN GENERATING A FEW ISOLATED SHOWERS THIS
MORNING BETWEEN GRAND HAVEN AND LUDINGTON. AS THIS FEATURE PUSHES TO
THE EAST... A MORE UNIFORM WEST SOUTHWEST WIND FLOW SHOULD DEVELOP
OVER THE LAKE. THIS OUGHT TO END THE SHOWER THREAT AT THE LAKESHORE
BY 18Z AND THE BETTER SFC CONVERGENCE SHOULD BE FOCUSED INLAND AFTER
18Z.


PVA ACROSS OUR ENTIRE CWFA LOOKS FAIRLY IMPRESSIVE TONIGHT.
THEREFORE WE WILL CONTINUE TO MENTION A SLIGHT CHC FOR SHOWERS
ACROSS OUR CWFA... ESPECIALLY AFTER REVIEWING 00Z GFS GUIDANCE.

GIVEN THE UPPER LEVEL PATTERN SUNDAY INTO EARLY NEXT WEEK... WE WILL
NEED TO CONTINUE TO CARRY POPS THROUGH MONDAY AFTERNOON. IT STILL
APPEARS THAT POPS WILL INCREASE GRADUALLY... PARTICULARLY LATE
MONDAY AS THE PRIMARY SHORTWAVE MOVES IN. HOWEVER TIMING SHORTWAVES
IN THIS TYPE PATTERN IS TRICKY... AND POPS WILL REMAIN NECESSARY
SUNDAY THROUGH MONDAY.

IT SHOULD BE STRESSED THAT DRY CONDITIONS WILL PREVAIL THE MAJORITY
OF THE TIME THIS WEEKEND. OUR BEST CHC FOR RAIN SHOULD HOLD OFF
UNTIL LATE MONDAY.

&&

.LONG TERM...(330 AM EDT SAT SEP 6 2008)
(MONDAY NIGHT THROUGH FRIDAY)

NO SIGNIFICANT CHANGES TO THE EXTENDED PERIOD. THERE IS GENERALLY
GOOD MODEL AGREEMENT ON EVOLUTION OF A SHORTWAVE TROUGH EARLY IN THE
WEEK. WILL KEEP CHANCE POPS MONDAY NIGHT WITH DEEPER MOISTURE AND
PRECIP DEPARTING TO THE EAST BY 12Z TUESDAY. SFC HIGH BUILDS IN WITH
FAIR WEATHER FOR TUESDAY AND WEDNESDAY. DROPPED POPS FOR WEDNESDAY
NIGHT AS IT APPEARS RETURN MOISTURE AND OVERRUNNING SHOWERS WILL NOT
ARRIVE UNTIL AFTER 12Z THURSDAY. LOOKS LIKE A WIDESPREAD RAIN EVENT
FOR THURSDAY OR FRIDAY AS SHORTWAVE TROUGH AND SFC LOW ARRIVE WITH
TRAILING COLD FRONT PUSHING THROUGH BY THE END OF THE EXTENDED
PERIOD.

&&

.MARINE...(1150 AM EDT SAT SEP 6 2008)
THE POSSIBILITY OF WATERSPOUTS WAS DISCUSSED THIS MORNING AS THE
CUMULUS OVER THE LAKE ON VIS SATELLITE HAD A SIMILAR APPEARANCE TO
THE EVENT ABOUT A MONTH AGO. HOWEVER LIMITING FACTORS ARE THAT LK MI
SFC WATERS TEMPS ARE IN THE MID 40S TO MID 50S IN THE VICINITY OF
THE SHOWERS AND THE DEPTH OF THE CONVECTIVE LAYER IS RELATIVELY
SHALLOW.

&&

.AVIATION...(717 AM EDT SAT SEP 6 2008)
SOME FOG AT JXN THIS MORNING SHOULD DISSIPATE BY 14Z...OTHERWISE VFR
EXPECTED TODAY AND TONIGHT AS HIGH PRESSURE BUILDS IN.

&&

.HYDROLOGY...(330 AM EDT SAT SEP 6 2008)
RAINFALL AMOUNTS THIS WEEKEND WILL AVERAGE BELOW ONE HALF INCH AND
RAIN WILL BE SCATTERED IN COVERAGE. THIS SHOULD HAVE LITTLE TO NO
IMPACT ON THE CURRENT HYDRO SITUATION.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.

&&

$$

SYNOPSIS:     LAURENS
SHORT TERM:   LAURENS/MEADE
LONG TERM:    OSTUNO
MARINE:       MEADE
AVIATION:     OSTUNO
HYDROLOGY:    LAURENS

000
FXUS63 KAPX 061439
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1039 AM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 724 AM/

A WEAK UPPER MIDWEST STORM SYSTEM...WILL MOVE OVER UPPER MICHIGAN
TODAY...BEFORE QUICKLY EXITING INTO ONTARIO THIS EVENING. THIS
FEATURE WILL GENERATE A FEW LIGHT RAIN SHOWERS OVER NORTHERN
MICHIGAN THROUGH THE AFTERNOON. SWR

&&

.SHORT TERM.../ISSUED AT 1037 AM/...THIS AFTERNOON

WEAK SURFACE LOW OVER WESTERN UPPER MICHIGAN IS GETTING
LEFT BEHIND PARENT SHORTWAVE TROUGH LIFTING ACROSS SOUTHERN
ONTARIO.  AREA OF SCATTERED SHOWERS IS MOSTLY CONFINED TO EASTERN
UPPER MICHIGAN WHERE BETTER ISENTROPIC ASCENT ON THE 295-300K
SURFACES IS LOCATED.  FARTHER SOUTH...WEAK COOL FRONT/SURFACE TROUGH
IS EXTENDING OVER NORTHERN LAKE MICHIGAN AND SOUTH ALONG THE EASTERN
SHORE OF LAKE MICHIGAN TO SE WISCONSIN...AND IS KICKING OFF ISOLATED
SHOWERS/SPRINKLES FROM LEELANAU PENINSULA TO LAKE COUNTY.
AFOREMENTIONED WEAK SURFACE LOW WILL SLOWLY SHIFT TO THE NE TOWARDS
LAKE SUPERIOR DURING THE AFTERNOON WHILE ITS COOL FRONT/TROUGH WILL
SHIFT SLOWLY EAST.  EXPECT SCT SHOWER ACTIVITY OVER NORTHERN
PORTIONS OF THE FORECAST AREA TO EXIT/DIMINISH BY MID-AFTERNOON WHEN
AREA OF ISENTROPIC ASCENT LIFTS NE INTO ONTARIO.  THINK WE WILL
CONTINUE TO SEE ISOLATED LIGHT SHOWERS/SPRINKLES POP UP ALONG THE
COOL FRONT AS IT SHIFTS EAST INTO NORTH-CENTRAL AND NE LOWER WITH A
LOOSE LOW LEVEL THETAE AXIS IN PLACE. ADJUSTED POP GRIDS TO REFLECT
THESE TRENDS AS WELL AS SOME CLEARING OVER NW LOWER LATE IN THE
AFTERNOON AS DRIER MID-LEVEL AIR WORKS IN.  OTHERWISE...VERY FEW
CHANGES MADE ELSEWHERE.

MPC

&&

.LONG TERM.../ISSUED AT 330 AM/...TONIGHT ONWARD

MODELS STILL STRUGGLE RESOLVING THE INDIVIDUAL WAVES WITHIN THE
BROADER UPPER TROF OVER THE NORTH CENTRAL US. THEY DO HOWEVER AGREE
ON WHEN THE BEST FORCING FOR PRECIP WILL BE...SUNDAY NIGHT AND AGAIN
MONDAY NIGHT.

TONIGHT...A SOMEWHAT WEAK SHORTWAVE WILL QUICKLY LIFT ENE ACROSS FAR
NORTHERN LOWER MI IN THE EVENING. IN ITS WAKE...THE WEAK SURFACE LOW
IN CENTRAL UPPER MI WILL DRIFT EASTWARD AND EVENTUALLY FILL. THE
BEST CHANCE FOR ANY PRECIP WILL BE IN THE EVENING IN EASTERN
UPPER...ONCE AGAIN WHERE MID LEVEL FORCING AND LOW/MID LEVEL SW
FLOW/ISENTROPIC ASCENT MATCH UP. BOTH OF THESE FALL APART LATE
TONIGHT. WILL HAVE SCT SHOWERS NORTH OF THE BRIDGE IN THE EVENING/
EARLY OVERNIGHT...DIMINISHING TO ISOLATED BY DAWN. EXTREME NORTHERN
LOWER WILL HAVE ISOLATED SHRA EARLY ON...WITH LITTLE PRECIP SOUTH OF
M-68. MOSTLY CLOUDY NORTH...PARTLY CLOUDY SOUTH (WHERE SOME BOG FOG
IS AGAIN POSSIBLE). MIN TEMPS LOW/MID 50S COASTS TO MID 40S IN THE
INTERIOR COOL SPOTS.

SUNDAY...MAIN ACTION SHOULD BE TO OUR SOUTH. A PAIR OF REASONABLY
VIGOROUS SHORTWAVES WILL RACE ENE INTO FAR SOUTHERN LOWER MI. A
ILL-DEFINED E-W SURFACE BOUNDARY WILL RESULT...ALSO WELL DOWNSTATE.
DEEPER MOISTURE WILL EVENTUALLY GET DRAWN NORTHWARD INTO OUR
SOUTHERN ZONES LATE IN THE DAY. WILL HAVE ISOLATED SHOWERS IN THE
MORNING IN THE SOUTH...EXPANDING ACROSS THE AREA IN THE AFTERNOON
WITH CHANCY (30-40) POPS IN THE SOUTH. INSTABILITY IS STILL MEAGER
(UP TO 300J/KG MUCAPE)...AND WILL NOT MENTION THUNDER. MAX TEMPS A
COUPLE DEGREES WARMER THAN TODAY...UPPER 60S TO LOWER 70S.

SUNDAY NIGHT/MONDAY...BEST SHOT OF RAIN FOR THE EVENT THUS FAR LOOKS
TO BE SUNDAY NIGHT...AS VORT RIBBON LIFTS NORTH FROM DOWNSTATE. A
SURFACE COLD FRONT WILL ALSO MOVE THRU THE FORECAST AREA FROM THE
NW. AND NOT QUITE WILLING TO GO WITH LIKELY POPS JUST YET...BUT WILL
BOOST TO 50 ACROSS THE ENTIRE AREA SUNDAY NIGHT. MONDAY MAY SEE A
RELATIVE LULL...WITH MID LEVEL SUBSIDENCE FOR AT LEAST PART OF THE
DAY AS VORT RIBBON PULLS OUT. REDUCED POPS A SMIDGE TO THE 30-40
RANGE. LOW TEMPS MAINLY AROUND 50. COLD ADVECTION MONDAY WILL KEEP
HIGHS MAINLY IN THE 60S.

REST OF THE FORECAST...ONE LAST MID-LEVEL TROF IN THE EPISODE WILL
GO THRU MONDAY NIGHT...WITH A RESULTING INCREASE IN PRECIP CHANCES.
STILL LOOKS LIKE WE DRY OUT MID-WEEK...BEFORE RETURN FLOW GETS GOING
WED NIGHT. TUESDAY WILL BE COOL LIKE MONDAY...WITH SOME RECOVERY IN
TEMPS INTO WED.

JZ

&&

.MARINE.../ISSUED AT 330 AM/

NO MARINE HEADLINES. DISORGANIZED PATTERN WILL KEEP SURFACE WINDS
LIGHT UNTIL SUNDAY NIGHT...AHEAD OF A COLD FRONT APPROACHING FROM
THE NW.

JZ

&&

.AVIATION.../ISSUED AT 724 AM /

MAINLY VFR. SHOWERS THAT DEVELOPED OVER LAKE MICHIGAN DURING THE
NIGHT HAVE WEAKENED...BUT COULD STILL BRING SPRINKLES OR LIGHT RAIN
TO TVC/PLN FOR A COUPLE OF HOURS. LOW PRESSURE IN WESTERN UPPER MI
WILL MOVE SLOWLY EASTWARD ACROSS UPPER MI THRU THE PERIOD. A WEAK
UPPER DISTURBANCE MAY BRING SOME SHOWERS NEAR PLN THIS AFTERNOON/
EARLY EVENING. NOT OUT OF THE QUESTION FOR SOME LIGHT FOG TONIGHT...
THOUGH THE BEST CHANCE WILL IN INLAND FROM ALL TAF SITES.

JZ

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KMQT 061143 AAA
AFDMQT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MARQUETTE MI
743 AM EDT SAT SEP 6 2008

UPDATED AVIATION DISCUSSION FOR 12Z TAF ISSUANCE

.DISCUSSION...
UPPER AIR PATTERN CONSISTS OF A 500 MB RIDGE OFF THE EAST COAST AND
WEST COASTS AND A LONGWAVE TROUGH ACROSS THE CENTRAL U.S. WITH
NUMEROUS SHORTWAVES EMBEDDED IN THE TROUGH. ON SHORTWAVE IS ACROSS
NORTHERN WI AND THIS HAS KICKED OFF SOME SHOWERS. THIS SHORTWAVE
MOVES THROUGH THIS MORNING AND THE TROUGH STAYS ACROSS THE AREA
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK.

NAM TAKING 850-500 MB Q-VECTOR CONVERGENCE AND SOME MOISTURE AND
MOVES THEM OUT TONIGHT BEFORE RETURNING THEM BOTH SUN EVENING AND
RETURNING BOTH AGAIN MON NIGHT. GFS SHOWS ABOUT THE SAME THING AND
WILL USE A BLEND OF THE ECMWF/GFS AND NAM FOR THIS FORECAST. LOOKS
UNSETTLED FOR A WHILE AND THERE WILL BE CHANCES OF RAIN THROUGH MOST
OF THIS WEEKEND...HOWEVER A WIDESPREAD AND HEAVY RAINFALL DOES NOT
LOOK LIKELY AT THIS TIME. OVERALL...DID NOT MAKE TOO MANY CHANGES TO
THE GOING FORECAST. DID REMOVE THUNDER THOUGH FROM THE FORECAST AS
INSTABILITY IS MARGINAL ENOUGH FOR IT AT THIS TIME. TEMPERATURES
LOOKED GOOD AND MADE VERY FEW CHANGES. ABUNDANT AND DEEP MOISTURE DO
NOT LOOK LIKELY EITHER...SO KEPT CHANCE POPS IN THERE.

&&

.AVIATION (FOR THE 12Z TAF ISSUANCE)...

UPPER LEVEL DISTURBANCE WHICH BROUGHT -SHRA ACROSS BOTH TAF SITES IS
RAPIDLY HEADING OFF TO THE NE. PLENTY OF CLOUDS LINGER IN ITS
WAKE...MOSTLY IN THE MVFR RANGE. SAW JUST WENT UP TO VFR BUT IMAGINE
ONCE THE RAIN STOPS THAT THE CIG MAY DROP BACK TO MVFR. FOR THE REST
OF THE DAY...SOME ISOLD -SHRA MAY AFFECT CMX WITH LINGERING MOISTURE
AND WEAK FORCING AROUND. HOWEVER...GIVEN THE COVERAGE AND THAT ANY
SHOULD NOT RESTRICT VSBY MUCH...HAVE DECLINED TO MENTION THEM IN THE
TAF. CIGS SHOULD GENERALLY STAY MVFR...ESPECIALLY WITH A WEST WIND
PROGGED TO DEVELOP THERE THAT CAN HELP IN UPSLOPING THE LOW LEVEL
MOISTURE. AT SAW...CIGS WILL CLIMB TO VFR IN THE AFTN THANKS TO
DAYTIME HEATING. THIS HEATING COULD DEVELOP SOME -SHRA AS WELL...BUT
SIMILARLY TO CMX...HAVE DECLINED TO MENTION THEM. ANTICYCLONIC FLOW
FROM A RIDGE OF HIGH PRESSURE MOVING IN THIS EVNG...COMBINED WITH
DRY AIR ADVECTION SHOULD ALLOW BOTH TAF SITES TO AT LEAST SCATTER
OUT ANY CLOUDS AROUND BY 00Z...THUS RESULTING IN VFR CONDITIONS.
SHOULD SKIES GO COMPLETELY CLEAR...THERE COULD BE SOME FOG...BUT
CONFIDENCE IS TOO LOW TO MENTION ATTM.

&&

.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...

LOW PRESSURE OVER NW WI WILL BE MOVING ACROSS LAKE SUPERIOR TODAY
AND TONIGHT. WINDS UP TO 20 KT ARE POSSIBLE TODAY...MAINLY AROUND
THE LOW OVER WEST AND CENTRAL LAKE SUPERIOR. HOWEVER...THERE COULD
BE A PERIOD TONIGHT OVER SOUTHERN LAKE SUPERIOR OF UP TO 25 KT WEST
WINDS ON THE SOUTH SIDE OF THE LOW. WINDS WILL DIMINISH BELOW 20 KT
FOR SUN AS THE NEXT TROUGH APPROACHES FROM THE NW. IN THE WAKE OF
THIS TROUGH FOR SUN NIGHT INTO MON MORNING...COLD AIR IS EXPECTED TO
FLOW IN...RESULTING IN A PERIOD OF NW 15 TO 25 KT...POSSIBLY EVEN 30
KT WINDS. THE STRONGEST WINDS SHOULD OCCUR ON NORTH CENTRAL AND
EASTERN LAKE SUPERIOR MON MORNING. EXPECT WINDS TO DIMINISH MON AFTN
WITH WIND SPEED BELOW 20 KT FOR AFTER MIDNIGHT MON NIGHT INTO TUE AS
A RIDGE OF HIGH PRESSURE MOVES ACROSS. SOUTHERLY WINDS WILL ATTEMPT
TO PICK UP TUE NIGHT AS THE RIDGE HEADS OFF TO THE EAST...BUT
THINKING IS THAT STRONGER WINDS...UP TO 25 KT WILL HOLD OFF UNTIL
WED EVENING. THAT IS WHEN A TROUGH OF LOW PRESSURE APPROACHES FROM
THE PLAINS.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

DISCUSSION...GJM
AVIATION...AJ
MARINE...AJ

000
FXUS63 KAPX 061125 RRA
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
724 AM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 724 AM/

A WEAK UPPER MIDWEST STORM SYSTEM...WILL MOVE OVER UPPER MICHIGAN
TODAY...BEFORE QUICKLY EXITING INTO ONTARIO THIS EVENING. THIS
FEATURE WILL GENERATE A FEW LIGHT RAIN SHOWERS OVER NORTHERN
MICHIGAN THROUGH THE AFTERNOON. SWR

&&

.SHORT TERM.../ISSUED AT 330 AM/...TODAY

FAIRLY VIGOROUS SHORTWAVE LIFTING ENE ACROSS WI EARLY THIS MORNING.
A WEAK SURFACE REFLECTION IS FOUND AS A 1013MB LOW OVER WESTERN
UPPER MI. INITIAL MID LEVEL RADAR RETURNS ARE VIRGA. HOWEVER...
CONVERGING LAND BREEZES OVER LAKE MI (WHERE DELTA T/S ARE IN THE
LOWER TEENS) WERE FORCING SOME SHOWERS THERE. TO THE WEST...SURFACE
OBS ARE SHOWING SOME SHOWERS REACHING THE GROUND AS FAR EAST AS THE
WI SHORELINE OF LAKE MI.

THE WEAK SURFACE LOW TO OUR NW IS PROGGED TO GET LEFT BEHIND BY THE
DEPARTING SHORTWAVE...TAKING ALL DAY AND ALL NIGHT TO SLOWLY CROSS
UPPER MI. THIS WILL PRODUCE PERSISTENT SW LOW-TO-MID LEVEL FLOW
TODAY...AND CORRESPONDING WEAK WARM/MOIST ADVECTION. A QUASI WARM
FRONT...NOW DRAPED FROM THE WI/MI BORDER TO CENTRAL LAKE MI...WILL
GRADUALLY WORK EASTWARD INTO NORTHERN MI TODAY. FORCING ALOFT IS
ACTUALLY STRONGEST EARLY THIS MORNING (WHEN WE STILL HAVE SOME DRY
MID-LEVEL AIR TO OVERCOME). BUT SOME SECONDARY FORCING MAY ARRIVE
THIS AFTERNOON...AS ANOTHER WEAKER VORT MAX ARRIVES FROM THE WEST.
THE AFTERNOON WAVE ALSO BRINGS SOMEWHAT STEEPER LAPSE RATES...AROUND
6C/KM FROM 700-500MB IN THE NW HALF OF THE FORECAST AREA. THAT
SAID...ABSOLUTE INSTABILITY IS NEVER ALL THAT IMPRESSIVE...UP TO
200J/KG OF MUCAPE.

THE BEST SUPPORT FOR PRECIP WILL BE IN THE NORTHERN HALF OF THE
FORECAST AREA...WHERE SW 850-700MB FLOW AND ISENTROPIC ASCENT IS
STRONGEST (RELATIVELY SPEAKING). WILL HAVE SCT SHRA NORTH OF
M-32...ISOLATED SOUTH...WITH PRECIP DEVELOPING EASTWARD WITH TIME.
WILL STEER TOWARD THE COOL SIDE OF TEMP GUIDANCE...THANKS TO
CONSIDERABLE CLOUD COVER. MAX TEMPS FROM THE MID 60S TO NEAR 70.

JZ

&&

.LONG TERM.../ISSUED AT 330 AM/...TONIGHT ONWARD

MODELS STILL STRUGGLE RESOLVING THE INDIVIDUAL WAVES WITHIN THE
BROADER UPPER TROF OVER THE NORTH CENTRAL US. THEY DO HOWEVER AGREE
ON WHEN THE BEST FORCING FOR PRECIP WILL BE...SUNDAY NIGHT AND AGAIN
MONDAY NIGHT.

TONIGHT...A SOMEWHAT WEAK SHORTWAVE WILL QUICKLY LIFT ENE ACROSS FAR
NORTHERN LOWER MI IN THE EVENING. IN ITS WAKE...THE WEAK SURFACE LOW
IN CENTRAL UPPER MI WILL DRIFT EASTWARD AND EVENTUALLY FILL. THE
BEST CHANCE FOR ANY PRECIP WILL BE IN THE EVENING IN EASTERN
UPPER...ONCE AGAIN WHERE MID LEVEL FORCING AND LOW/MID LEVEL SW
FLOW/ISENTROPIC ASCENT MATCH UP. BOTH OF THESE FALL APART LATE
TONIGHT. WILL HAVE SCT SHOWERS NORTH OF THE BRIDGE IN THE EVENING/
EARLY OVERNIGHT...DIMINISHING TO ISOLATED BY DAWN. EXTREME NORTHERN
LOWER WILL HAVE ISOLATED SHRA EARLY ON...WITH LITTLE PRECIP SOUTH OF
M-68. MOSTLY CLOUDY NORTH...PARTLY CLOUDY SOUTH (WHERE SOME BOG FOG
IS AGAIN POSSIBLE). MIN TEMPS LOW/MID 50S COASTS TO MID 40S IN THE
INTERIOR COOL SPOTS.

SUNDAY...MAIN ACTION SHOULD BE TO OUR SOUTH. A PAIR OF REASONABLY
VIGOROUS SHORTWAVES WILL RACE ENE INTO FAR SOUTHERN LOWER MI. A
ILL-DEFINED E-W SURFACE BOUNDARY WILL RESULT...ALSO WELL DOWNSTATE.
DEEPER MOISTURE WILL EVENTUALLY GET DRAWN NORTHWARD INTO OUR
SOUTHERN ZONES LATE IN THE DAY. WILL HAVE ISOLATED SHOWERS IN THE
MORNING IN THE SOUTH...EXPANDING ACROSS THE AREA IN THE AFTERNOON
WITH CHANCY (30-40) POPS IN THE SOUTH. INSTABILITY IS STILL MEAGER
(UP TO 300J/KG MUCAPE)...AND WILL NOT MENTION THUNDER. MAX TEMPS A
COUPLE DEGREES WARMER THAN TODAY...UPPER 60S TO LOWER 70S.

SUNDAY NIGHT/MONDAY...BEST SHOT OF RAIN FOR THE EVENT THUS FAR LOOKS
TO BE SUNDAY NIGHT...AS VORT RIBBON LIFTS NORTH FROM DOWNSTATE. A
SURFACE COLD FRONT WILL ALSO MOVE THRU THE FORECAST AREA FROM THE
NW. AND NOT QUITE WILLING TO GO WITH LIKELY POPS JUST YET...BUT WILL
BOOST TO 50 ACROSS THE ENTIRE AREA SUNDAY NIGHT. MONDAY MAY SEE A
RELATIVE LULL...WITH MID LEVEL SUBSIDENCE FOR AT LEAST PART OF THE
DAY AS VORT RIBBON PULLS OUT. REDUCED POPS A SMIDGE TO THE 30-40
RANGE. LOW TEMPS MAINLY AROUND 50. COLD ADVECTION MONDAY WILL KEEP
HIGHS MAINLY IN THE 60S.

REST OF THE FORECAST...ONE LAST MID-LEVEL TROF IN THE EPISODE WILL
GO THRU MONDAY NIGHT...WITH A RESULTING INCREASE IN PRECIP CHANCES.
STILL LOOKS LIKE WE DRY OUT MID-WEEK...BEFORE RETURN FLOW GETS GOING
WED NIGHT. TUESDAY WILL BE COOL LIKE MONDAY...WITH SOME RECOVERY IN
TEMPS INTO WED.

JZ

&&

.MARINE.../ISSUED AT 330 AM/

NO MARINE HEADLINES. DISORGANIZED PATTERN WILL KEEP SURFACE WINDS
LIGHT UNTIL SUNDAY NIGHT...AHEAD OF A COLD FRONT APPROACHING FROM
THE NW.

JZ

&&

.AVIATION.../ISSUED AT 724 AM /

MAINLY VFR. SHOWERS THAT DEVELOPED OVER LAKE MICHIGAN DURING THE
NIGHT HAVE WEAKENED...BUT COULD STILL BRING SPRINKLES OR LIGHT RAIN
TO TVC/PLN FOR A COUPLE OF HOURS. LOW PRESSURE IN WESTERN UPPER MI
WILL MOVE SLOWLY EASTWARD ACROSS UPPER MI THRU THE PERIOD. A WEAK
UPPER DISTURBANCE MAY BRING SOME SHOWERS NEAR PLN THIS AFTERNOON/
EARLY EVENING. NOT OUT OF THE QUESTION FOR SOME LIGHT FOG TONIGHT...
THOUGH THE BEST CHANCE WILL IN INLAND FROM ALL TAF SITES.

JZ

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KAPX 061125
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
330 AM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 724 AM/

A WEAK UPPER MIDWEST STORM SYSTEM...WILL MOVE OVER UPPER MICHIGAN
TODAY...BEFORE QUICKLY EXITING INTO ONTARIO THIS EVENING. THIS
FEATURE WILL GENERATE A FEW LIGHT RAIN SHOWERS OVER NORTHERN
MICHIGAN THROUGH THE AFTERNOON. SWR

&&

.SHORT TERM.../ISSUED AT 330 AM/...TODAY

FAIRLY VIGOROUS SHORTWAVE LIFTING ENE ACROSS WI EARLY THIS MORNING.
A WEAK SURFACE REFLECTION IS FOUND AS A 1013MB LOW OVER WESTERN
UPPER MI. INITIAL MID LEVEL RADAR RETURNS ARE VIRGA. HOWEVER...
CONVERGING LAND BREEZES OVER LAKE MI (WHERE DELTA T/S ARE IN THE
LOWER TEENS) WERE FORCING SOME SHOWERS THERE. TO THE WEST...SURFACE
OBS ARE SHOWING SOME SHOWERS REACHING THE GROUND AS FAR EAST AS THE
WI SHORELINE OF LAKE MI.

THE WEAK SURFACE LOW TO OUR NW IS PROGGED TO GET LEFT BEHIND BY THE
DEPARTING SHORTWAVE...TAKING ALL DAY AND ALL NIGHT TO SLOWLY CROSS
UPPER MI. THIS WILL PRODUCE PERSISTENT SW LOW-TO-MID LEVEL FLOW
TODAY...AND CORRESPONDING WEAK WARM/MOIST ADVECTION. A QUASI WARM
FRONT...NOW DRAPED FROM THE WI/MI BORDER TO CENTRAL LAKE MI...WILL
GRADUALLY WORK EASTWARD INTO NORTHERN MI TODAY. FORCING ALOFT IS
ACTUALLY STRONGEST EARLY THIS MORNING (WHEN WE STILL HAVE SOME DRY
MID-LEVEL AIR TO OVERCOME). BUT SOME SECONDARY FORCING MAY ARRIVE
THIS AFTERNOON...AS ANOTHER WEAKER VORT MAX ARRIVES FROM THE WEST.
THE AFTERNOON WAVE ALSO BRINGS SOMEWHAT STEEPER LAPSE RATES...AROUND
6C/KM FROM 700-500MB IN THE NW HALF OF THE FORECAST AREA. THAT
SAID...ABSOLUTE INSTABILITY IS NEVER ALL THAT IMPRESSIVE...UP TO
200J/KG OF MUCAPE.

THE BEST SUPPORT FOR PRECIP WILL BE IN THE NORTHERN HALF OF THE
FORECAST AREA...WHERE SW 850-700MB FLOW AND ISENTROPIC ASCENT IS
STRONGEST (RELATIVELY SPEAKING). WILL HAVE SCT SHRA NORTH OF
M-32...ISOLATED SOUTH...WITH PRECIP DEVELOPING EASTWARD WITH TIME.
WILL STEER TOWARD THE COOL SIDE OF TEMP GUIDANCE...THANKS TO
CONSIDERABLE CLOUD COVER. MAX TEMPS FROM THE MID 60S TO NEAR 70.

JZ

&&

.LONG TERM.../ISSUED AT 330 AM/...TONIGHT ONWARD

MODELS STILL STRUGGLE RESOLVING THE INDIVIDUAL WAVES WITHIN THE
BROADER UPPER TROF OVER THE NORTH CENTRAL US. THEY DO HOWEVER AGREE
ON WHEN THE BEST FORCING FOR PRECIP WILL BE...SUNDAY NIGHT AND AGAIN
MONDAY NIGHT.

TONIGHT...A SOMEWHAT WEAK SHORTWAVE WILL QUICKLY LIFT ENE ACROSS FAR
NORTHERN LOWER MI IN THE EVENING. IN ITS WAKE...THE WEAK SURFACE LOW
IN CENTRAL UPPER MI WILL DRIFT EASTWARD AND EVENTUALLY FILL. THE
BEST CHANCE FOR ANY PRECIP WILL BE IN THE EVENING IN EASTERN
UPPER...ONCE AGAIN WHERE MID LEVEL FORCING AND LOW/MID LEVEL SW
FLOW/ISENTROPIC ASCENT MATCH UP. BOTH OF THESE FALL APART LATE
TONIGHT. WILL HAVE SCT SHOWERS NORTH OF THE BRIDGE IN THE EVENING/
EARLY OVERNIGHT...DIMINISHING TO ISOLATED BY DAWN. EXTREME NORTHERN
LOWER WILL HAVE ISOLATED SHRA EARLY ON...WITH LITTLE PRECIP SOUTH OF
M-68. MOSTLY CLOUDY NORTH...PARTLY CLOUDY SOUTH (WHERE SOME BOG FOG
IS AGAIN POSSIBLE). MIN TEMPS LOW/MID 50S COASTS TO MID 40S IN THE
INTERIOR COOL SPOTS.

SUNDAY...MAIN ACTION SHOULD BE TO OUR SOUTH. A PAIR OF REASONABLY
VIGOROUS SHORTWAVES WILL RACE ENE INTO FAR SOUTHERN LOWER MI. A
ILL-DEFINED E-W SURFACE BOUNDARY WILL RESULT...ALSO WELL DOWNSTATE.
DEEPER MOISTURE WILL EVENTUALLY GET DRAWN NORTHWARD INTO OUR
SOUTHERN ZONES LATE IN THE DAY. WILL HAVE ISOLATED SHOWERS IN THE
MORNING IN THE SOUTH...EXPANDING ACROSS THE AREA IN THE AFTERNOON
WITH CHANCY (30-40) POPS IN THE SOUTH. INSTABILITY IS STILL MEAGER
(UP TO 300J/KG MUCAPE)...AND WILL NOT MENTION THUNDER. MAX TEMPS A
COUPLE DEGREES WARMER THAN TODAY...UPPER 60S TO LOWER 70S.

SUNDAY NIGHT/MONDAY...BEST SHOT OF RAIN FOR THE EVENT THUS FAR LOOKS
TO BE SUNDAY NIGHT...AS VORT RIBBON LIFTS NORTH FROM DOWNSTATE. A
SURFACE COLD FRONT WILL ALSO MOVE THRU THE FORECAST AREA FROM THE
NW. AND NOT QUITE WILLING TO GO WITH LIKELY POPS JUST YET...BUT WILL
BOOST TO 50 ACROSS THE ENTIRE AREA SUNDAY NIGHT. MONDAY MAY SEE A
RELATIVE LULL...WITH MID LEVEL SUBSIDENCE FOR AT LEAST PART OF THE
DAY AS VORT RIBBON PULLS OUT. REDUCED POPS A SMIDGE TO THE 30-40
RANGE. LOW TEMPS MAINLY AROUND 50. COLD ADVECTION MONDAY WILL KEEP
HIGHS MAINLY IN THE 60S.

REST OF THE FORECAST...ONE LAST MID-LEVEL TROF IN THE EPISODE WILL
GO THRU MONDAY NIGHT...WITH A RESULTING INCREASE IN PRECIP CHANCES.
STILL LOOKS LIKE WE DRY OUT MID-WEEK...BEFORE RETURN FLOW GETS GOING
WED NIGHT. TUESDAY WILL BE COOL LIKE MONDAY...WITH SOME RECOVERY IN
TEMPS INTO WED.

JZ

&&

.MARINE.../ISSUED AT 330 AM/

NO MARINE HEADLINES. DISORGANIZED PATTERN WILL KEEP SURFACE WINDS
LIGHT UNTIL SUNDAY NIGHT...AHEAD OF A COLD FRONT APPROACHING FROM
THE NW.

JZ

&&

.AVIATION.../ISSUED AT 724 AM /

MAINLY VFR. SHOWERS THAT DEVELOPED OVER LAKE MICHIGAN DURING THE
NIGHT HAVE WEAKENED...BUT COULD STILL BRING SPRINKLES OR LIGHT RAIN
TO TVC/PLN FOR A COUPLE OF HOURS. LOW PRESSURE IN WESTERN UPPER MI
WILL MOVE SLOWLY EASTWARD ACROSS UPPER MI THRU THE PERIOD. A WEAK
UPPER DISTURBANCE MAY BRING SOME SHOWERS NEAR PLN THIS AFTERNOON/
EARLY EVENING. NOT OUT OF THE QUESTION FOR SOME LIGHT FOG TONIGHT...
THOUGH THE BEST CHANCE WILL IN INLAND FROM ALL TAF SITES.

JZ

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KGRR 061117
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
717 AM EDT SAT SEP 6 2008

LATEST UPDATE...AVIATION...

.SYNOPSIS...(330 AM EDT SAT SEP 6 2008)
AN UPPER LEVEL TROUGH ACROSS THE MID SECTION OF THE NATION WILL
RESULT IN A SOMEWHAT UNSETTLED WEATHER PATTERN THROUGH EARLY NEXT
WEEK. SEVERAL UPPER LEVEL DISTURBANCES WILL LEAD TO SEVERAL CHANCES
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. HOWEVER DRY
CONDITIONS WILL PREVAIL THE MAJORITY OF THE TIME THIS WEEKEND AND
OUR BEST CHANCE FOR PRECIPITATION SHOULD HOLD OFF UNTIL LATE MONDAY.

&&

.SHORT TERM...(330 AM EDT SAT SEP 6 2008)
(TODAY THROUGH MONDAY AFTERNOON)

A SHORTWAVE CURRENTLY OVER THE CENTRAL PLAINS STATES WILL HEAD TO
THE ENE TODAY. THIS FEATURE COULD TRIGGER DEVELOPMENT OF A FEW
SHOWERS ACROSS OUR NORTHERN CWFA... SO WE MAINTAINED LOW POPS ACROSS
THAT AREA. IN FACT A FEW SHOWERS ARE ALREADY DEVELOPING ATTM JUST
WEST OF LDM.

PVA ACROSS OUR ENTIRE CWFA LOOKS FAIRLY IMPRESSIVE TONIGHT.
THEREFORE WE WILL CONTINUE TO MENTION A SLIGHT CHC FOR SHOWERS
ACROSS OUR CWFA... ESPECIALLY AFTER REVIEWING 00Z GFS GUIDANCE.

GIVEN THE UPPER LEVEL PATTERN SUNDAY INTO EARLY NEXT WEEK... WE WILL
NEED TO CONTINUE TO CARRY POPS THROUGH MONDAY AFTERNOON. IT STILL
APPEARS THAT POPS WILL INCREASE GRADUALLY... PARTICULARLY LATE
MONDAY AS THE PRIMARY SHORTWAVE MOVES IN. HOWEVER TIMING SHORTWAVES
IN THIS TYPE PATTERN IS TRICKY... AND POPS WILL REMAIN NECESSARY
SUNDAY THROUGH MONDAY.

IT SHOULD BE STRESSED THAT DRY CONDITIONS WILL PREVAIL THE MAJORITY
OF THE TIME THIS WEEKEND. OUR BEST CHC FOR RAIN SHOULD HOLD OFF
UNTIL LATE MONDAY.

&&

.LONG TERM...(330 AM EDT SAT SEP 6 2008)
(MONDAY NIGHT THROUGH FRIDAY)

NO SIGNIFICANT CHANGES TO THE EXTENDED PERIOD. THERE IS GENERALLY
GOOD MODEL AGREEMENT ON EVOLUTION OF A SHORTWAVE TROUGH EARLY IN THE
WEEK. WILL KEEP CHANCE POPS MONDAY NIGHT WITH DEEPER MOISTURE AND
PRECIP DEPARTING TO THE EAST BY 12Z TUESDAY. SFC HIGH BUILDS IN WITH
FAIR WEATHER FOR TUESDAY AND WEDNESDAY. DROPPED POPS FOR WEDNESDAY
NIGHT AS IT APPEARS RETURN MOISTURE AND OVERRUNNING SHOWERS WILL NOT
ARRIVE UNTIL AFTER 12Z THURSDAY. LOOKS LIKE A WIDESPREAD RAIN EVENT
FOR THURSDAY OR FRIDAY AS SHORTWAVE TROUGH AND SFC LOW ARRIVE WITH
TRAILING COLD FRONT PUSHING THROUGH BY THE END OF THE EXTENDED
PERIOD.

&&

.MARINE...(330 AM EDT SAT SEP 6 2008)
WAVE ACTION THROUGH THIS WEEKEND SHOULD BE FAIRLY MINIMAL DUE TO A
FAIRLY WEAK WSW GRADIENT. A FEW SHOWERS COULD AFFECT MARINERS NORTH
OF MUSKEGON TODAY AND THEN ACROSS ALL AREAS TONIGHT THROUGH MONDAY
NIGHT.

&&

.AVIATION...(717 AM EDT SAT SEP 6 2008)
SOME FOG AT JXN THIS MORNING SHOULD DISSIPATE BY 14Z...OTHERWISE VFR
EXPECTED TODAY AND TONIGHT AS HIGH PRESSURE BUILDS IN.

&&

.HYDROLOGY...(330 AM EDT SAT SEP 6 2008)
RAINFALL AMOUNTS THIS WEEKEND WILL AVERAGE BELOW ONE HALF INCH AND
RAIN WILL BE SCATTERED IN COVERAGE. THIS SHOULD HAVE LITTLE TO NO
IMPACT ON THE CURRENT HYDRO SITUATION.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.

&&

$$

SYNOPSIS:     LAURENS
SHORT TERM:   LAURENS
LONG TERM:    OSTUNO
MARINE:       LAURENS
AVIATION:     OSTUNO
HYDROLOGY:    LAURENS

000
FXUS63 KDTX 061108
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
708 AM EDT SAT SEP 6 2008

.AVIATION...

A FEW SMALL POCKETS OF MVFR STRATUS WILL QUICKLY LIFT THROUGH MID
MORNING.  OTHERWISE...VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD
AS WEAK HIGH PRESSURE EXTENDS EASTWARD INTO THE REGION.  THE
APPROACH OF A WEAK TROUGH WILL BRING SOME INCREASE IN HIGHER
CLOUDINESS LATE IN THE DAY AND OVERNIGHT.  WINDS WILL REMAIN LIGHT
THROUGH THE PERIOD.

&&

.PREV DISCUSSION...ISSUED 330 AM EDT SAT SEP 6 2008

SHORT TERM...TODAY

BROAD UPPER LEVEL TROUGHING NOW ENCOMPASSING MUCH OF THE CENTRAL
CONUS WILL ALLOW SEVERAL WEAKER SHORTWAVES TO TRANSLATE
EAST-NORTHEAST WITHIN THE MEAN FLOW OVER THE COMING DAYS.  LATEST
WATER VAPOR IMAGERY SHOWS THE FIRST OF THESE IMPULSES SHEARING
NORTHEAST INTO SOUTHWEST WI...WHILE A SECOND WAVE PUSHES TOWARD
WESTERN IA.   MEANWHILE...BROAD AREA OF HIGH PRESSURE CENTERED OVER
THE CENTRAL PLAINS BEGINNING TO EXTEND NORTHEAST INTO SOUTHEAST
LOWER MI.  STUBBORN LOW STRATUS HANGING ON LOCALLY BENEATH A STRONG
INVERSION...ALTHOUGH SATELLITE TRENDS INDICATING A FEW MORE BREAKS
DEVELOPING WITHIN THIS DECK ESPECIALLY WEST OF I-75.

WEAK HIGH PRESSURE WILL REMAIN THE PREDOMINANT LARGE SCALE FEATURE
ACROSS SOUTHEAST LOWER MI TODAY.  ALTHOUGH THE MODEL MOISTURE FIELDS
ARE SHOWING SOME DIFFICULTY IN HANDLING THE CURRENT STRATUS
DECK...WOULD EXPECT EVENTUAL SCATTERING/LIFTING OF ANY LINGERING
STRATUS BY LATE MORNING AS THE LOW LEVEL THERMAL TROUGH PUSHES
EAST.  WEAK SHORTWAVE SHEARING NORTHEAST FROM IOWA TO CENTRAL LOWER
MI MAY BRING SOME ADDITIONAL MID LEVEL CLOUDINESS BY LATE
AFTERNOON.   ALTHOUGH THERE REMAINS A LACK OF GOOD FORCING OR
MOISTURE ADVECTION ASSOCIATED WITH THIS SYSTEM...CANNOT RULE OUT A
LIGHT SHOWER/ SPRINKLES ACROSS MIDLAND/BAY COUNTIES AS A WEAK SFC
TROUGH LIFTS THROUGH.

AIRMASS WILL MODERATE SLIGHTLY FROM YESTERDAY...AIDED BY A FAIR
AMOUNT OF INSOLATION.  THIS WILL MAINTAIN HIGHS AROUND NORMAL IN THE
LOW/MID 70S.

LONG TERM...

NEAR NORMAL TEMPERATURES LOOK TO GIVE WAY TO BELOW NORMAL TEMPS
BY MIDWEEK...ALONG WITH AN INCREASING CHANCE OF RAIN THROUGH
MONDAY NIGHT.

RATHER AMPLIFIED UPPER LEVEL TROUGH OVER THE ROCKIES/CENTRAL CONUS
WILL TRANSITION TO A BIT MORE ZONAL FLOW OVER THE NORTHERN
CONUS...BEFORE SHARPENING TROUGH AXIS TRACKS THROUGH THE GREAT LAKES
REGION BY MID WEEK. SEVERAL CHANCES FOR RAIN WITH NUMEROUS
SHORTWAVES TRAVELING WITHIN THE JET STREAM. BEST CHANCE OF RAIN
APPEARS TO BE LATE MONDAY/MONDAY NIGHT...WITH VERY TIGHT BAROCLINIC
ZONE SETTING UP OVER THE SOUTHERN GREAT LAKES AND RAPID CYCLOGENESIS
TAKING PLACE...PER 00Z GFS/EUROPEAN/CANADIAN GLOBAL...WITH GOOD
ISENTROPIC ASCENT PROGGED. SIGNIFICANT LOW LEVEL COLD ADVECTION IN
THE LOWS WAKE TUESDAY MORNING...AS 850 MB TEMPS FORECASTED TO FALL
INTO THE MID SINGLE NUMBERS...LIKELY HOLDING MAX TEMPS IN THE UPPER
60S TO AROUND 70 DEGREES. THIS SHOULD SET UP A VERY COOL NIGHT
TUESDAY NIGHT AS HIGH PRESSURE BUILDS INTO SOUTHEAST
MICHIGAN...ALLOWING TEMPS TO DROP INTO THE 40S. OTHERWISE...LOOKING
FOR NEAR NORMAL TEMPS (IN LINE WITH MAV GUIDANCE) DURING THE NEXT
COUPLE OF DAYS.

MARINE...

HIGH PRESSURE NOSING NORTHEAST INTO THE CENTRAL GREAT LAKES ALLOWING
WINDS TO WEAKEN OVERNIGHT...LEADING TO A REDUCTION IN WAVE HEIGHTS.
THUS...THE REMAINING SMALL CRAFT ADVISORIES WILL BE DROPPED EARLY
THIS MORNING.  OTHERWISE...FAVORABLE BOATING CONDITIONS WILL EXIST
THROUGH THE DURATION OF THE WEEKEND AS HIGH PRESSURE EXPANDS EAST
ACROSS THE REGION.  ANOTHER LOW PRESSURE SYSTEM WILL BRING THE NEXT
COLD FRONT THROUGH THE REGION ON MONDAY...POTENTIALLY CREATING MORE
UNSTABLE CONDITIONS BY MONDAY NIGHT AND TUESDAY AS MUCH COOLER AIR
FILTERS ACROSS THE WARMER LAKE WATERS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....MR
SHORT TERM...MR
LONG TERM....SF
MARINE.......MR


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

000
FXUS63 KGRR 060736
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 AM EDT SAT SEP 6 2008

LATEST UPDATE...ALL EXCEPT AVIATION...

.SYNOPSIS...(330 AM EDT SAT SEP 6 2008)
AN UPPER LEVEL TROUGH ACROSS THE MID SECTION OF THE NATION WILL
RESULT IN A SOMEWHAT UNSETTLED WEATHER PATTERN THROUGH EARLY NEXT
WEEK. SEVERAL UPPER LEVEL DISTURBANCES WILL LEAD TO SEVERAL CHANCES
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. HOWEVER DRY
CONDITIONS WILL PREVAIL THE MAJORITY OF THE TIME THIS WEEKEND AND
OUR BEST CHANCE FOR PRECIPITATION SHOULD HOLD OFF UNTIL LATE MONDAY.

&&

.SHORT TERM...(330 AM EDT SAT SEP 6 2008)
(TODAY THROUGH MONDAY AFTERNOON)

A SHORTWAVE CURRENTLY OVER THE CENTRAL PLAINS STATES WILL HEAD TO
THE ENE TODAY. THIS FEATURE COULD TRIGGER DEVELOPMENT OF A FEW
SHOWERS ACROSS OUR NORTHERN CWFA... SO WE MAINTAINED LOW POPS ACROSS
THAT AREA. IN FACT A FEW SHOWERS ARE ALREADY DEVELOPING ATTM JUST
WEST OF LDM.

PVA ACROSS OUR ENTIRE CWFA LOOKS FAIRLY IMPRESSIVE TONIGHT.
THEREFORE WE WILL CONTINUE TO MENTION A SLIGHT CHC FOR SHOWERS
ACROSS OUR CWFA... ESPECIALLY AFTER REVIEWING 00Z GFS GUIDANCE.

GIVEN THE UPPER LEVEL PATTERN SUNDAY INTO EARLY NEXT WEEK... WE WILL
NEED TO CONTINUE TO CARRY POPS THROUGH MONDAY AFTERNOON. IT STILL
APPEARS THAT POPS WILL INCREASE GRADUALLY... PARTICULARLY LATE
MONDAY AS THE PRIMARY SHORTWAVE MOVES IN. HOWEVER TIMING SHORTWAVES
IN THIS TYPE PATTERN IS TRICKY... AND POPS WILL REMAIN NECESSARY
SUNDAY THROUGH MONDAY.

IT SHOULD BE STRESSED THAT DRY CONDITIONS WILL PREVAIL THE MAJORITY
OF THE TIME THIS WEEKEND. OUR BEST CHC FOR RAIN SHOULD HOLD OFF
UNTIL LATE MONDAY.

&&

.LONG TERM...(330 AM EDT SAT SEP 6 2008)
(MONDAY NIGHT THROUGH FRIDAY)

NO SIGNIFICANT CHANGES TO THE EXTENDED PERIOD. THERE IS GENERALLY
GOOD MODEL AGREEMENT ON EVOLUTION OF A SHORTWAVE TROUGH EARLY IN THE
WEEK. WILL KEEP CHANCE POPS MONDAY NIGHT WITH DEEPER MOISTURE AND
PRECIP DEPARTING TO THE EAST BY 12Z TUESDAY. SFC HIGH BUILDS IN WITH
FAIR WEATHER FOR TUESDAY AND WEDNESDAY. DROPPED POPS FOR WEDNESDAY
NIGHT AS IT APPEARS RETURN MOISTURE AND OVERRUNNING SHOWERS WILL NOT
ARRIVE UNTIL AFTER 12Z THURSDAY. LOOKS LIKE A WIDESPREAD RAIN EVENT
FOR THURSDAY OR FRIDAY AS SHORTWAVE TROUGH AND SFC LOW ARRIVE WITH
TRAILING COLD FRONT PUSHING THROUGH BY THE END OF THE EXTENDED
PERIOD.

&&

.MARINE...(330 AM EDT SAT SEP 6 2008)
WAVE ACTION THROUGH THIS WEEKEND SHOULD BE FAIRLY MINIMAL DUE TO A
FAIRLY WEAK WSW GRADIENT. A FEW SHOWERS COULD AFFECT MARINERS NORTH
OF MUSKEGON TODAY AND THEN ACROSS ALL AREAS TONIGHT THROUGH MONDAY
NIGHT.

&&

.AVIATION...(1250 AM EDT SAT SEP 6 2008)
WENT WITH VFR CONDITIONS FOR ALL AREAS. CIGS AROUND 4000 FT
HAVE SPREAD INTO MUCH OF SW LOWER MI. IF THIS PERSISTS...THE FOG
THREAT SHOULD BE LIMITED AND REMAIN LOCALIZED IN NATURE. THERE IS A
CHANCE THAT WE COULD SEE DECREASING CLOUDS AFT 09Z...WHICH WOULD
ALLOW COVERAGE OF FOG TO PICK UP A BIT JUST BEFORE SUNRISE.
HOWEVER...THERE IS TOO LITTLE CERTAINTY FOR FOG AT THIS TIME TO
MENTION AT ANY OF THE TAF SITES.

&&

.HYDROLOGY...(330 AM EDT SAT SEP 6 2008)
RAINFALL AMOUNTS THIS WEEKEND WILL AVERAGE BELOW ONE HALF INCH AND
RAIN WILL BE SCATTERED IN COVERAGE. THIS SHOULD HAVE LITTLE TO NO
IMPACT ON THE CURRENT HYDRO SITUATION.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.

&&

$$

SYNOPSIS:     LAURENS
SHORT TERM:   LAURENS
LONG TERM:    OSTUNO
MARINE:       LAURENS
AVIATION:     TJT/OSTUNO
HYDROLOGY:    LAURENS

000
FXUS63 KDTX 060730
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
330 AM EDT SAT SEP 6 2008

.SHORT TERM...TODAY

BROAD UPPER LEVEL TROUGHING NOW ENCOMPASSING MUCH OF THE CENTRAL
CONUS WILL ALLOW SEVERAL WEAKER SHORTWAVES TO TRANSLATE
EAST-NORTHEAST WITHIN THE MEAN FLOW OVER THE COMING DAYS.  LATEST
WATER VAPOR IMAGERY SHOWS THE FIRST OF THESE IMPULSES SHEARING
NORTHEAST INTO SOUTHWEST WI...WHILE A SECOND WAVE PUSHES TOWARD
WESTERN IA.   MEANWHILE...BROAD AREA OF HIGH PRESSURE CENTERED OVER
THE CENTRAL PLAINS BEGINNING TO EXTEND NORTHEAST INTO SOUTHEAST
LOWER MI.  STUBBORN LOW STRATUS HANGING ON LOCALLY BENEATH A STRONG
INVERSION...ALTHOUGH SATELLITE TRENDS INDICATING A FEW MORE BREAKS
DEVELOPING WITHIN THIS DECK ESPECIALLY WEST OF I-75.

WEAK HIGH PRESSURE WILL REMAIN THE PREDOMINANT LARGE SCALE FEATURE
ACROSS SOUTHEAST LOWER MI TODAY.  ALTHOUGH THE MODEL MOISTURE FIELDS
ARE SHOWING SOME DIFFICULTY IN HANDLING THE CURRENT STRATUS
DECK...WOULD EXPECT EVENTUAL SCATTERING/LIFTING OF ANY LINGERING
STRATUS BY LATE MORNING AS THE LOW LEVEL THERMAL TROUGH PUSHES
EAST.  WEAK SHORTWAVE SHEARING NORTHEAST FROM IOWA TO CENTRAL LOWER
MI MAY BRING SOME ADDITIONAL MID LEVEL CLOUDINESS BY LATE
AFTERNOON.   ALTHOUGH THERE REMAINS A LACK OF GOOD FORCING OR
MOISTURE ADVECTION ASSOCIATED WITH THIS SYSTEM...CANNOT RULE OUT A
LIGHT SHOWER/ SPRINKLES ACROSS MIDLAND/BAY COUNTIES AS A WEAK SFC
TROUGH LIFTS THROUGH.

AIRMASS WILL MODERATE SLIGHTLY FROM YESTERDAY...AIDED BY A FAIR
AMOUNT OF INSOLATION.  THIS WILL MAINTAIN HIGHS AROUND NORMAL IN THE
LOW/MID 70S.

&&

.LONG TERM...

NEAR NORMAL TEMPERATURES LOOK TO GIVE WAY TO BELOW NORMAL TEMPS
BY MIDWEEK...ALONG WITH AN INCREASING CHANCE OF RAIN THROUGH
MONDAY NIGHT.

RATHER AMPLIFIED UPPER LEVEL TROUGH OVER THE ROCKIES/CENTRAL CONUS
WILL TRANSITION TO A BIT MORE ZONAL FLOW OVER THE NORTHERN
CONUS...BEFORE SHARPENING TROUGH AXIS TRACKS THROUGH THE GREAT LAKES
REGION BY MID WEEK. SEVERAL CHANCES FOR RAIN WITH NUMEROUS
SHORTWAVES TRAVELING WITHIN THE JET STREAM. BEST CHANCE OF RAIN
APPEARS TO BE LATE MONDAY/MONDAY NIGHT...WITH VERY TIGHT BAROCLINIC
ZONE SETTING UP OVER THE SOUTHERN GREAT LAKES AND RAPID CYCLOGENESIS
TAKING PLACE...PER 00Z GFS/EUROPEAN/CANADIAN GLOBAL...WITH GOOD
ISENTROPIC ASCENT PROGGED. SIGNIFICANT LOW LEVEL COLD ADVECTION IN
THE LOWS WAKE TUESDAY MORNING...AS 850 MB TEMPS FORECASTED TO FALL
INTO THE MID SINGLE NUMBERS...LIKELY HOLDING MAX TEMPS IN THE UPPER
60S TO AROUND 70 DEGREES. THIS SHOULD SET UP A VERY COOL NIGHT
TUESDAY NIGHT AS HIGH PRESSURE BUILDS INTO SOUTHEAST
MICHIGAN...ALLOWING TEMPS TO DROP INTO THE 40S. OTHERWISE...LOOKING
FOR NEAR NORMAL TEMPS (IN LINE WITH MAV GUIDANCE) DURING THE NEXT
COUPLE OF DAYS.

&&

.MARINE...

HIGH PRESSURE NOSING NORTHEAST INTO THE CENTRAL GREAT LAKES ALLOWING
WINDS TO WEAKEN OVERNIGHT...LEADING TO A REDUCTION IN WAVE HEIGHTS.
THUS...THE REMAINING SMALL CRAFT ADVISORIES WILL BE DROPPED EARLY
THIS MORNING.  OTHERWISE...FAVORABLE BOATING CONDITIONS WILL EXIST
THROUGH THE DURATION OF THE WEEKEND AS HIGH PRESSURE EXPANDS EAST
ACROSS THE REGION.  ANOTHER LOW PRESSURE SYSTEM WILL BRING THE NEXT
COLD FRONT THROUGH THE REGION ON MONDAY...POTENTIALLY CREATING MORE
UNSTABLE CONDITIONS BY MONDAY NIGHT AND TUESDAY AS MUCH COOLER AIR
FILTERS ACROSS THE WARMER LAKE WATERS.

&&

.PREV DISCUSSION...ISSUED 103 AM EDT SAT SEP 6 2008

AVIATION...

THE 00Z DTX SOUNDING SHOWED A STRONG INVERSION BASED NEAR 4500 FT
WITH A SHALLOW LAYER OF MOISTURE UNDER THIS INVERSION. RECENT
SATELLITE TRENDS INDICATE THAT THE STRATUS FIELD HAS BEEN EXPANDING
UNDERNEATH THIS INVERSION. EXPECT THE VFR STRATUS DECK WILL PERSIST
THROUGH MOST OF THE MORNING UNTIL DAYTIME HEATING ALLOWS THE CLOUDS
TO LIFT INTO A SCATTERED CU FIELD AROUND 15Z. THERE HAVE BEEN SOME
MVFR STRATO CU REPORTED AROUND PHN AS A RESULT OF THE MOISTURE FLUX
OFF LAKE HURON. THE LOW LEVEL FLOW IS FORECAST TO VEER SLIGHTLY MORE
NORTH-NORTHEASTERLY THROUGH THE MORNING...WHICH MAY BRING SOME OF
THESE LOWER CLOUDS INTO THE DETROIT AREA AROUND DAYBREAK. MBS HAS
BEEN RIGHT ON THE EDGE OF THE CLOUDS. WEAK LOW LEVEL DRY AIR
ADVECTION UNDER NORTHERLY FLOW SHOULD STILL PROVIDE AN OVERALL
CLEARING TREND AT MBS DURING THE MORNING...WHICH WOULD PROVIDE SOME
OPPORTUNITY FOR RADIATIONAL FOG DEVELOPMENT AROUND DAYBREAK. HAVE
THUS INTRODUCED SOME MVFR VSBY RESTRICTIONS AT MBS TO ACCOUNT FOR
THIS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...MR
LONG TERM....SF
MARINE.......MR
AVIATION.....SC


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

000
FXUS63 KAPX 060730
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
330 AM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 330 AM/

COOL NORTHWEST FLOW ALOFT AND WEAK DISTURBANCES WILL BRING PERIODIC
SHOWER CHANCES AND SEASONABLY COOL TEMPERATURES TO THE REGION
THROUGH AT LEAST MONDAY.  MSB

&&

.SHORT TERM.../ISSUED AT 330 AM/...TODAY

FAIRLY VIGOROUS SHORTWAVE LIFTING ENE ACROSS WI EARLY THIS MORNING.
A WEAK SURFACE REFLECTION IS FOUND AS A 1013MB LOW OVER WESTERN
UPPER MI. INITIAL MID LEVEL RADAR RETURNS ARE VIRGA. HOWEVER...
CONVERGING LAND BREEZES OVER LAKE MI (WHERE DELTA T/S ARE IN THE
LOWER TEENS) WERE FORCING SOME SHOWERS THERE. TO THE WEST...SURFACE
OBS ARE SHOWING SOME SHOWERS REACHING THE GROUND AS FAR EAST AS THE
WI SHORELINE OF LAKE MI.

THE WEAK SURFACE LOW TO OUR NW IS PROGGED TO GET LEFT BEHIND BY THE
DEPARTING SHORTWAVE...TAKING ALL DAY AND ALL NIGHT TO SLOWLY CROSS
UPPER MI. THIS WILL PRODUCE PERSISTENT SW LOW-TO-MID LEVEL FLOW
TODAY...AND CORRESPONDING WEAK WARM/MOIST ADVECTION. A QUASI WARM
FRONT...NOW DRAPED FROM THE WI/MI BORDER TO CENTRAL LAKE MI...WILL
GRADUALLY WORK EASTWARD INTO NORTHERN MI TODAY. FORCING ALOFT IS
ACTUALLY STRONGEST EARLY THIS MORNING (WHEN WE STILL HAVE SOME DRY
MID-LEVEL AIR TO OVERCOME). BUT SOME SECONDARY FORCING MAY ARRIVE
THIS AFTERNOON...AS ANOTHER WEAKER VORT MAX ARRIVES FROM THE WEST.
THE AFTERNOON WAVE ALSO BRINGS SOMEWHAT STEEPER LAPSE RATES...AROUND
6C/KM FROM 700-500MB IN THE NW HALF OF THE FORECAST AREA. THAT
SAID...ABSOLUTE INSTABILITY IS NEVER ALL THAT IMPRESSIVE...UP TO
200J/KG OF MUCAPE.

THE BEST SUPPORT FOR PRECIP WILL BE IN THE NORTHERN HALF OF THE
FORECAST AREA...WHERE SW 850-700MB FLOW AND ISENTROPIC ASCENT IS
STRONGEST (RELATIVELY SPEAKING). WILL HAVE SCT SHRA NORTH OF
M-32...ISOLATED SOUTH...WITH PRECIP DEVELOPING EASTWARD WITH TIME.
WILL STEER TOWARD THE COOL SIDE OF TEMP GUIDANCE...THANKS TO
CONSIDERABLE CLOUD COVER. MAX TEMPS FROM THE MID 60S TO NEAR 70.

JZ

&&

.LONG TERM.../ISSUED AT 330 AM/...TONIGHT ONWARD

MODELS STILL STRUGGLE RESOLVING THE INDIVIDUAL WAVES WITHIN THE
BROADER UPPER TROF OVER THE NORTH CENTRAL US. THEY DO HOWEVER AGREE
ON WHEN THE BEST FORCING FOR PRECIP WILL BE...SUNDAY NIGHT AND AGAIN
MONDAY NIGHT.

TONIGHT...A SOMEWHAT WEAK SHORTWAVE WILL QUICKLY LIFT ENE ACROSS FAR
NORTHERN LOWER MI IN THE EVENING. IN ITS WAKE...THE WEAK SURFACE LOW
IN CENTRAL UPPER MI WILL DRIFT EASTWARD AND EVENTUALLY FILL. THE
BEST CHANCE FOR ANY PRECIP WILL BE IN THE EVENING IN EASTERN
UPPER...ONCE AGAIN WHERE MID LEVEL FORCING AND LOW/MID LEVEL SW
FLOW/ISENTROPIC ASCENT MATCH UP. BOTH OF THESE FALL APART LATE
TONIGHT. WILL HAVE SCT SHOWERS NORTH OF THE BRIDGE IN THE EVENING/
EARLY OVERNIGHT...DIMINISHING TO ISOLATED BY DAWN. EXTREME NORTHERN
LOWER WILL HAVE ISOLATED SHRA EARLY ON...WITH LITTLE PRECIP SOUTH OF
M-68. MOSTLY CLOUDY NORTH...PARTLY CLOUDY SOUTH (WHERE SOME BOG FOG
IS AGAIN POSSIBLE). MIN TEMPS LOW/MID 50S COASTS TO MID 40S IN THE
INTERIOR COOL SPOTS.

SUNDAY...MAIN ACTION SHOULD BE TO OUR SOUTH. A PAIR OF REASONABLY
VIGOROUS SHORTWAVES WILL RACE ENE INTO FAR SOUTHERN LOWER MI. A
ILL-DEFINED E-W SURFACE BOUNDARY WILL RESULT...ALSO WELL DOWNSTATE.
DEEPER MOISTURE WILL EVENTUALLY GET DRAWN NORTHWARD INTO OUR
SOUTHERN ZONES LATE IN THE DAY. WILL HAVE ISOLATED SHOWERS IN THE
MORNING IN THE SOUTH...EXPANDING ACROSS THE AREA IN THE AFTERNOON
WITH CHANCY (30-40) POPS IN THE SOUTH. INSTABILITY IS STILL MEAGER
(UP TO 300J/KG MUCAPE)...AND WILL NOT MENTION THUNDER. MAX TEMPS A
COUPLE DEGREES WARMER THAN TODAY...UPPER 60S TO LOWER 70S.

SUNDAY NIGHT/MONDAY...BEST SHOT OF RAIN FOR THE EVENT THUS FAR LOOKS
TO BE SUNDAY NIGHT...AS VORT RIBBON LIFTS NORTH FROM DOWNSTATE. A
SURFACE COLD FRONT WILL ALSO MOVE THRU THE FORECAST AREA FROM THE
NW. AND NOT QUITE WILLING TO GO WITH LIKELY POPS JUST YET...BUT WILL
BOOST TO 50 ACROSS THE ENTIRE AREA SUNDAY NIGHT. MONDAY MAY SEE A
RELATIVE LULL...WITH MID LEVEL SUBSIDENCE FOR AT LEAST PART OF THE
DAY AS VORT RIBBON PULLS OUT. REDUCED POPS A SMIDGE TO THE 30-40
RANGE. LOW TEMPS MAINLY AROUND 50. COLD ADVECTION MONDAY WILL KEEP
HIGHS MAINLY IN THE 60S.

REST OF THE FORECAST...ONE LAST MID-LEVEL TROF IN THE EPISODE WILL
GO THRU MONDAY NIGHT...WITH A RESULTING INCREASE IN PRECIP CHANCES.
STILL LOOKS LIKE WE DRY OUT MID-WEEK...BEFORE RETURN FLOW GETS GOING
WED NIGHT. TUESDAY WILL BE COOL LIKE MONDAY...WITH SOME RECOVERY IN
TEMPS INTO WED.

JZ

&&

.MARINE.../ISSUED AT 330 AM/

NO MARINE HEADLINES. DISORGANIZED PATTERN WILL KEEP SURFACE WINDS
LIGHT UNTIL SUNDAY NIGHT...AHEAD OF A COLD FRONT APPROACHING FROM
THE NW.

JZ

&&

.AVIATION.../ISSUED AT 125 AM /

OVERALL...VFR CONDITIONS EXPECTED THRU THE TAF PERIOD. INITIAL
CONCERN WILL BE PATCHY FOG GIVEN RECENT RAIN AND INITIALLY CLEAR
SKIES (OUTSIDE OF SOME HIGH CLOUDS) WITH CALM WINDS. KAPN/KPLN STAND
TO SEE THE BEST SHOT AT FOG...WITH PERIODIC IFR CONDITIONS POSSIBLE.
OUTSIDE OF THAT...JUST SOME INCREASE IN MID CLOUD FROM WEST TO EAST
THRU SUNRISE...GIVING WAY TO LOWER CEILINGS (4-5KFT) THRU THE
MORNING AND EARLY AFTERNOON HOURS IN ADVANCE OF AN APPROACHING WEAK
SURFACE TROUGH. WILL LIKELY SEE SCATTERED SHOWERS MAKE A RUN TOWARD
KPLN BEFORE SUNRISE...WITH CHANCES EXTENDING TOWARD KAPN INTO EARLY
AFTERNOON. IMPROVING CONDITIONS THEN ANTICIPATED BY LATE
AFTERNOON/EARLY EVENING WITH THE ARRIVAL OF WEAK HIGH PRESSURE.

LAWRENCE

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KMQT 060715
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
315 AM EDT SAT SEP 6 2008

.DISCUSSION...
UPPER AIR PATTERN CONSISTS OF A 500 MB RIDGE OFF THE EAST COAST AND
WEST COASTS AND A LONGWAVE TROUGH ACROSS THE CENTRAL U.S. WITH
NUMEROUS SHORTWAVES EMBEDDED IN THE TROUGH. ON SHORTWAVE IS ACROSS
NORTHERN WI AND THIS HAS KICKED OFF SOME SHOWERS. THIS SHORTWAVE
MOVES THROUGH THIS MORNING AND THE TROUGH STAYS ACROSS THE AREA
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK.

NAM TAKING 850-500 MB Q-VECTOR CONVERGENCE AND SOME MOISTURE AND
MOVES THEM OUT TONIGHT BEFORE RETURNING THEM BOTH SUN EVENING AND
RETURNING BOTH AGAIN MON NIGHT. GFS SHOWS ABOUT THE SAME THING AND
WILL USE A BLEND OF THE ECMWF/GFS AND NAM FOR THIS FORECAST. LOOKS
UNSETTLED FOR A WHILE AND THERE WILL BE CHANCES OF RAIN THROUGH MOST
OF THIS WEEKEND...HOWEVER A WIDESPREAD AND HEAVY RAINFALL DOES NOT
LOOK LIKELY AT THIS TIME. OVERALL...DID NOT MAKE TOO MANY CHANGES TO
THE GOING FORECAST. DID REMOVE THUNDER THOUGH FROM THE FORECAST AS
INSTABILITY IS MARGINAL ENOUGH FOR IT AT THIS TIME. TEMPERATURES
LOOKED GOOD AND MADE VERY FEW CHANGES. ABUNDANT AND DEEP MOISTURE DO
NOT LOOK LIKELY EITHER...SO KEPT CHANCE POPS IN THERE.

&&

.AVIATION (FOR THE 06Z TAF ISSUANCE)...

-SHRA WHICH HAVE ARRIVED IN THE KCMX VCNTY WILL SPREAD TO KSAW OVER
THE NEXT FEW HRS AS LOW PRES MOVES FROM MN TO WRN LAKE SUPERIOR. PER
UPSTREAM OBS...EXPECT CONDITIONS INITIALLY TO BE VFR EVEN THOUGH
PCPN WILL BE OCCURRING. HOWEVER...AS PCPN DIMINISHES/ENDS...EXPECT
MVFR CONDITIONS TO DEVELOP WITH LOW CLOUD/FOG FORMING UNDER ARRIVAL
OF DRIER AIR ALOFT...AND ABOVE THE LOW-LEVELS MOISTENED BY PCPN.
THERE WILL BE SLOW IMPROVEMENT SAT MORNING WITH CONDITIONS BECOMING
VFR IN THE AFTN AND CONTINUING THRU THE END OF THIS FCST PERIOD.

&&

.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...

LOW PRESSURE OVER NW WI WILL BE MOVING ACROSS LAKE SUPERIOR TODAY
AND TONIGHT. WINDS UP TO 20 KT ARE POSSIBLE TODAY...MAINLY AROUND
THE LOW OVER WEST AND CENTRAL LAKE SUPERIOR. HOWEVER...THERE COULD
BE A PERIOD TONIGHT OVER SOUTHERN LAKE SUPERIOR OF UP TO 25 KT WEST
WINDS ON THE SOUTH SIDE OF THE LOW. WINDS WILL DIMINISH BELOW 20 KT
FOR SUN AS THE NEXT TROUGH APPROACHES FROM THE NW. IN THE WAKE OF
THIS TROUGH FOR SUN NIGHT INTO MON MORNING...COLD AIR IS EXPECTED TO
FLOW IN...RESULTING IN A PERIOD OF NW 15 TO 25 KT...POSSIBLY EVEN 30
KT WINDS. THE STRONGEST WINDS SHOULD OCCUR ON NORTH CENTRAL AND
EASTERN LAKE SUPERIOR MON MORNING. EXPECT WINDS TO DIMINISH MON AFTN
WITH WIND SPEED BELOW 20 KT FOR AFTER MIDNIGHT MON NIGHT INTO TUE AS
A RIDGE OF HIGH PRESSURE MOVES ACROSS. SOUTHERLY WINDS WILL ATTEMPT
TO PICK UP TUE NIGHT AS THE RIDGE HEADS OFF TO THE EAST...BUT
THINKING IS THAT STRONGER WINDS...UP TO 25 KT WILL HOLD OFF UNTIL
WED EVENING. THAT IS WHEN A TROUGH OF LOW PRESSURE APPROACHES FROM
THE PLAINS.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

DISCUSSION...GJM
AVIATION...ROLFSON
MARINE...AJ

000
FXUS63 KMQT 060526 AAB
AFDMQT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MARQUETTE MI
126 AM EDT SAT SEP 6 2008

UPDATED AVIATION DISCUSSION FOR 06Z TAFS

.SYNOPSIS... ISSUED AT 325 PM EDT

12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW UPR TROFFING
CENTERED OVER CNTRL NAMERICA BTWN RDGS ON THE E AND W COASTS.
SHRTWV/DEEP MSTR ASSOCIATED WITH THE REMNANTS OF GUSTAV ARE MOVING
RDPLY NE THRU SE CAN...BUT A SUBTLE LO PRES TROF REMAINS OVER THE FA
ON ITS WRN FLANK. RECENT TAMDAR SDNGS SHOW A GOOD AMT OF LLVL MSTR
REMAINS OVER THE UPR GRT LKS UNDER THE SUBSIDENCE INVRN ARND H75
LEFT IN ITS WAKE. SO QUITE A BIT OF SC IS PRESENT DESPITE DIURNAL
HTG THAT HAS LIFTED CLD BASE AND ENDED ANY -DZ THAT WAS OBSVD
EARLIER. THE COMBINATION OF SOME SUBSIDENCE OVER LK SUP RELATED TO
THE LK BREEZE CIRCULATION AND THE ARRIVAL OF SOMEWHAT DRIER AIR FM
THE NW THAT WAS SHOWN BEST ON THE 00Z RAOBS FM INL/YPL HAS TENDED TO
BREAK UP THE CLD MORE AGGRESSIVELY THERE AND NEAR THE LK SHORES.
NEXT SHRTWV OF CONCERN IS PRESENTLY MOVING ACRS NRN MN ALONG WITH AN
ASSOCIATED SFC LO. THERE IS QUITE A BIT OF CLD TO THE N AND W OF
THIS LO...AND THE ERN EDGE OF THE THICKER CLD IS MOVING TOWARD WRN
LK SUP. SOME SCT -SHRA ARE AS FAR E AS DLH IN AXIS OF HIER SPECIFIC
HUMIDITY SHOWN ON THE 300K ISENTROPIC SFC (ARND H7) BY THE 12Z NAM
F6. BUT OVERALL PCPN COVG SEEMS LIMITED BY THE DRY MID LVLS SHOWN ON
THE 12Z MPX RAOB.

&&

.SHORT TERM (TNGT AND SAT)... ISSUED AT 325 PM EDT

FOR TNGT...12Z GFS/NAM SHOW SHRTWV NOW OVER NRN MN SHEARING ENEWD
AND WEAKENING A BIT TO NEAR ISLE ROYALE BY 12Z SAT AS UPR TROF AXIS
REMAINS SITUATED IN THE PLAINS. THE ACCOMPANYING SFC LO IS PROGGED
TO REACH THE WRN SHORE OF THE U.P. BOTH MODELS SHOW AXIS OF HIEST
SPECIFIC HUMIDITY NOW OVER MN AND ON THE 300K SFC SHIFTING INTO THE
W THIS EVNG THEN THE ECNTRL BY 12Z SAT WITH ISENTROPIC LIFT NOTED ON
THE 295-305K SFCS/QVECTOR CNVGC IN THE H85-5 LYR. GFS IS A BIT MORE
GENEROUS WITH QPF...BUT PREFER THE SOMEWHAT MORE MODEST NAM GIVEN
THE MID LVL DRY AIR SHOWN ON THE 12Z MPX RAOB THAT IS LIMITING PCPN
COVG NOW. STILL...HAVE OPTED TO BUMP POPS UP TO 40 BEFORE FAIRLY
AGGRESSIVE DRYING ON THE 300K SFC IN THE JET SURGE REGION ON THE SE
FLANK OF THE SHRTWV TRACK OVERSPRDS THE FA. GOING FCST MIN TEMPS ARE
FAIRLY IN LINE WITH LATEST GFS/ETA/NGM MOS GUIDANCE...SO NO SGNFT
CHGS MADE TO GOING FCST.

ON SAT...THE DEEPER MSTR ALF WL IMPACT THE ERN ZNS IN THE MRNG
BEFORE THE DRYING ON THE 300K SFC IS FCST TO CLR ERY BY 18Z OR SO AS
THE SHRTWV NR ISLE ROYALE/SFC LO OVER WRN LK SUP AT 12Z SHIFTS NE
INTO ONTARIO. TO THE W...THE FOCUS SHIFTS TO WHETHER ENUF LLVL MSTR
WL LINGER TO ALLOW THE REDVLPMNT OF MORE SHRA WITH DIURNAL HTG. IF
THE TIME OF YEAR WERE CLOSER TO THE SUMMER SOLSTICE...THAT WOULD BE
A REAL CONCERN. OTHER CONSIDERATIONS INCLUDE THE PRESENCE OF
LINGERING LO CLD IN THE MRNG WHICH DVLPS WITH THE ARRIVAL OF THE
DRYING ALF LATE TNGT AND THAT WOULD LIMIT SFC HTG. CONSIDERING THE
MARGINAL LAPSE RATES AND MID LVL DRY AIR EXHIBITED IN GFS/NAM FCST
SDNGS IN THE ABSENCE OF DYNAMIC FORCING...BELIEVE REDVLPMNT OF
DIURNAL SHRA IN THE AFTN IS A LO POTENTIAL. SO ELECTED TO CUT GOING
GENERAL 30 POP TO NO MORE THAN 20.

.LONG TERM (SATURDAY NIGHT THROUGH FRIDAY)...

THIS PERIOD REMAINS PLAGUED BY WEAK SHORTWAVES...MAKING SPECIFIC
TIMING OF CLOUDS AND PRECIPITATION DIFFICULT.  FOR THE LONG TERM
THIS RESULTS IN AVERAGE FORECASTER CONFIDENCE IN THE SPECIFICS.

LINGERING PRECIPITATION WILL START OFF THIS PERIOD THANKS TO A
WEAK SHORTWAVE MOVING THROUGH THE CWA.  A SLIGHTLY STRONGER SYSTEM
IS FIGURED FOR SUNDAY AND SUNDAY NIGHT...MOVING THROUGH THE UPPER
GREAT LAKES.  THE POTENTIAL REMAINS FOR THUNDERSTORM
ACTIVITY...ALBEIT ISOLATED.  A COLD FRONT WILL BE POISED TO MOVE
WEST TO EAST OVER UPPER MICHIGAN LATE SUNDAY AFTERNOON THROUGH THE
EARLY OVERNIGHT HOURS.  THE ENTIRE SYSTEM IS THEN EXPECTED TO
STRENTHEN OVER SOUTHEASTERN ONTARIO AND LAKE HURON MONDAY MORNING.
THIS SHOULD KEEP NORTH TO NORTHWESTERLY WINDS AND A BETTER CHANCE OF
LINGERING CLOUDS ACROSS EASTERN UPPER MICHIGAN INTO AT LEAST MONDAY
AFTERNOON.

DRY WEATHER CAN THEN BE EXPECTED FOR THE MIDDLE OF THE UPCOMING WORK
WEEK...AS HIGH PRESSURE MOVES IN AT THE SURFACE AND A ZONAL FLOW
SETS UP AT 500MB.  HPC GUIDANCE WAS FOLLOWED PRETTY CLOSELY FOR THIS
PERIOD...EXCLUDING SKY COVER WHICH NEEDED TO BE MINIMIZED A LITTLE
MORE INITIALLY.  THIS WAS HEAVILY BASED ON ENSEMBLES...WITH A LEAN
TOWARDS THE 12Z GFS.  FOR THE LATTER HALF OF THE WORK WEEK
THOUGH...SOUTHWESTERLY FLOW WILL RETURN BRINGING A BETTER CHANCE OF
SHOWERS OR THUNDERSTORMS THURSDAY AND FRIDAY.

&&

.AVIATION (FOR THE 06Z TAF ISSUANCE)...

-SHRA WHICH HAVE ARRIVED IN THE KCMX VCNTY WILL SPREAD TO KSAW OVER
THE NEXT FEW HRS AS LOW PRES MOVES FROM MN TO WRN LAKE SUPERIOR. PER
UPSTREAM OBS...EXPECT CONDITIONS INITIALLY TO BE VFR EVEN THOUGH
PCPN WILL BE OCCURRING. HOWEVER...AS PCPN DIMINISHES/ENDS...EXPECT
MVFR CONDITIONS TO DEVELOP WITH LOW CLOUD/FOG FORMING UNDER ARRIVAL
OF DRIER AIR ALOFT...AND ABOVE THE LOW-LEVELS MOISTENED BY PCPN.
THERE WILL BE SLOW IMPROVEMENT SAT MORNING WITH CONDITIONS BECOMING
VFR IN THE AFTN AND CONTINUING THRU THE END OF THIS FCST PERIOD.

&&

.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...

LOW PRESSURE OVER FAR WESTERN QUEBEC WILL WEAKEN AS IT MOVES OVER
NEW BRUNSWICK SATURDAY MORNING WHILE A HIGH PRESSURE RIDGE OVER
WESTERN LAKE SUPERIOR THIS EVENING MOVES OVER THE EASTERN GREAT
LAKES ON SUNDAY. MEANWHILE...A TROUGH OF LOW PRESSURE WILL CROSS
LAKE SUPERIOR SATURDAY. ANOTHER DEEPER LOW PRESSURE TROUGH WILL
FOLLOW LATE SUNDAY INTO MONDAY...WITH HIGH PRESSURE BUILDING OVER
THE LOWER GREAT LAKES MONDAY. THIS HIGH WILL SHIFT INTO THE EASTERN
GREAT LAKES ON WEDNESDAY. WINDS THROUGH THE WEEKEND WILL BE NO
HIGHER THAN 20 KNOTS. THE NEXT CHANCE FOR STRONGER WINDS WILL BE ON
MONDAY. NORTHWEST WINDS THEN ARE LIKELY TO REACH 25 KNOTS...
ESPECIALLY OVER THE EAST HALF...AS HIGH PRESSURE FOLLOWS THE TROUGH
INTO THE UPPER GREAT LAKES.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

SYNOPSIS/SHORT TERM...KC
LONG TERM...KF
AVIATION...ROLFSON
MARINE...KC

000
FXUS63 KAPX 060522
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
125 AM EDT SAT SEP 6 2008

.SYNOPSIS.../ISSUED AT 330 PM/

HIGH PRESSURE CONTINUES TO BUILD INTO THE WRN GREAT LAKES REGION
LATE THIS AFTERNOON IN THE WAKE OF A DEPARTING AREA OF LOW PRESSURE
(I.E. REMNANTS OF GUSTAV). CLOUDS ARE DECREASING FROM NW TO SE
ACROSS MICHIGAN AS DRIER AIR WORKS INTO THE REGION. HOWEVER...
ADDITIONAL CLOUDS AND LIGHT PRECIP ARE DEVELOPING OVER THE PLAINS
STATES AND THE UPPER MISSISSIPPI VALLEY ALONG AND AHEAD OF A
DEVELOPING LOW PRESSURE SYSTEM. OVERALL PATTERN WILL REMAIN FAIRLY
ACTIVE FOR THE NEXT WEEK AS A BROAD UPPER TROUGH OVER THE NRN US
GRADUALLY EVOLVES INTO BROAD UPPER RIDGING ACROSS THE ERN US BY THE
MIDDLE OF NEXT WEEK.

&&

.SHORT TERM.../ISSUED AT 951 PM/...OVERNIGHT

OVERALL...GOING FCST IN PRETTY GOOD SHAPE...WITH ONLY MINOR
CHANGES MADE. LATE EVENING WATER VAPOR PICS SHOW RATHER IMPRESSIVE
BUT COMPACT SHORTWAVE LIFTING INTO FAR SOUTHWEST WISCONSIN...
DRIVING DECENT RAIN SHIELD INTO CENTRAL PORTIONS OF THAT STATE.
BIGGEST ISSUE FOR THE OVERNIGHT DEALS WITH RAINFALL POTENTIAL WITH
THIS SYSTEM AS THE UPR WAVE SLOWLY SHEARS OUT INTO SOUTHERN
ONTARIO BY MID MORNING. QUICK BUT MODEST SHOT OF QG UPWARD
SUPPORT/310K ISENTROPIC UPGLIDE/LOW-MID LEVEL MOISTURE TRANSPORT
IN COMBINATION WITH NAM/GFS/SREF MODEL SIGNAL ARGUE FOR AN UPTICK
TO LIKELY POPS TOWARD THE 09Z HOUR ACRS WESTERN MACKINAC
COUNTY...WITH CHANCY POPS EXTENDED FURTHER EAST TO NEAR THE LAKE
MICHIGAN SHORELINE. OTHERWISE...HAVE TWEAKED CLOUD COVER DOWN ACRS
THE EAST EARLY ON (WITH EXPECTED FURTHER LOSS OF LINGERING
STRATOCU)...WITH CLOUDS ON THE INCREASE MOST SPOTS THRU THE NIGHT
WITH APPROACH OF MID/UPR LEVEL RH PLUME. OVERNIGHT LOWS IN THE
40S/LOW 50S LOOK GREAT...AND GIVEN SOAKING RAIN OVER THE LAST 36
HOURS...SHOULD HAVE LITTLE TROUBLE REALIZING FOG IN A QUITE A FEW
SPOTS PRIOR TO ARRIVAL OF THICKER CLOUD COVER.

LAWRENCE

&&

.LONG TERM.../ISSUED AT 330 PM/...SATURDAY THRU FRIDAY

SATURDAY...WEAK TROUGH WILL SWING THRU NRN MICHIGAN THROUGHOUT THE
DAY. MOISTURE IS SOMEWHAT LIMITED...LIFT IS RATHER WEAK AND
INSTABILITY IS UNIMPRESSIVE. HOWEVER...THERE IS JUST ENOUGH OF ALL
THREE TO WARRANT CHANCE POPS FOR THE WRN TWO-THIRDS OF THE CWA IN
THE MORNING...SPREADING INTO THE REST OF THE CWA IN THE AFTERNOON.
WILL LEAVE OUT A MENTION OF THUNDER DUE TO INSUFFICIENT MID LEVEL
INSTABILITY (700-500 MB LAPSE RATES OF 5.5 C/KM) AND LIMITED LOW
LEVEL DESTABILIZATION DUE TO MAINLY CLOUDY SKIES. HIGH TEMPS WILL
WARM BACK INTO THE UPPER 60S AND LOWER 70S.

SATURDAY NIGHT...A COUPLE WEAK IMPULSES WILL PASS NEARBY NORTHERN
MICHIGAN.  ONE SUCH WAVE WILL MOVE ACROSS EASTERN LAKE SUPERIOR
DURING THE EVENING WITH SOME MINOR BUT STILL DEEP LAYER -DIVQ AND A
LOOSE 850MB THETAE AXIS.  A SECOND WAVE ARRIVES LATE SATURDAY
NIGHT/EARLY SUNDAY MORNING ACROSS CENTRAL AND SOUTHERN LAKE MICHIGAN
WITH ADDITIONAL MID/UPPER LEVEL -DIV Q.  WITH BOTH PIECES OF ENERGY
HOWEVER...MOISTURE IS RELATIVELY SCANT AND MID-LEVEL LAPSE RATES ARE
POOR.  THERE IS A LOOSELY PACKED LOW LEVEL THETAE AXIS THAT PASSES
ACROSS EASTERN UPPER AND NE LOWER DURING THE EVENING...AND THAT
PROBABLY IS THE BEST CHANCE OF SEEING ANY SPOTTY SHOWERS.

SUNDAY...ANOTHER PERIOD WHERE MOST OF THE DAY WILL BE DRY.
ADDITIONAL SHORTWAVE/CHANNELED VORT ENERGY WILL SWING ACROSS THE
SOUTHERN GREAT LAKES WHILE A MORE POTENT NORTHERN STREAM TROUGH WILL
PUSH A COOL FRONT TOWARDS THE NW GREAT LAKES.  ISENTROPIC ASCENT
INCREASES AS THESE FEATURES DRAW CLOSER BY AFTERNOON ACROSS THE
SOUTHERN AND WESTERN FORECAST AREA...BUT BEST -DIVQ WILL RESIDE
UPSTREAM ON THE OTHER SIDE OF LAKE MICHIGAN.  WILL TRIM BACK POPS A
BIT...KEEPING ISOLATED SHOWER WORDING ACROSS THE WESTERN FORECAST
AREA DURING THE AFTERNOON.

SUNDAY NIGHT...SHORTWAVE TROUGH MOVES ACROSS ONTARIO AND LAKE
SUPERIOR WITH THE ASSOCIATED COLD FRONT CROSSING MOST OF THE
FORECAST AREA OVERNIGHT.  BEST FORCING APPEARS TO BE OVER NORTHERN
PORTIONS OF THE CWA IN THE FORM OF UPPER DIVERGENCE AND -DIVQ.
THERE ARE SOME ALSO MODERATELY STEEPED 700-500MB LAPSE RATES
ACCORDING TO THE GFS/ECMWF GETTING CLOSE TO 6.5C/KM SO WILL MAINTAIN
THUNDER CHANCES GOING.

MONDAY THROUGH FRIDAY...MODELS ARE IN DECENT AGREEMENT THROUGH ABOUT
WEDNESDAY BEFORE DIFFERENCES EMERGE BETWEEN THE MEDIUM RANGE
OPERATIONAL MODELS.  THE GENERAL CONSENSUS BASICALLY SHOWS A
RELATIVELY LOW AMPLITUDE PATTERN WITH A FLATTEN RIDGING OFF THE WEST
COAST OF NORTH AMERICA AND ALSO OVER THE WESTERN ATLANTIC WITH
FLATTEN TROUGHING IN-BETWEEN.  THIS PATTERN SLOWLY SHIFTS EAST DURING
THE PERIOD AND THE 06Z GFS HAS THE MOST SUPPORT FROM THE 00Z
ENSEMBLE MEMBERS.  THE 00Z ECMWF HANGS SHORTWAVE ENERGY ACROSS THE
INTERMOUNTAIN WEST WHICH HAS IMPLICATIONS DOWNSTREAM FOR THE GREAT
LAKES...AND IS AN OUTLIER WITH THE ENSEMBLE MEMBERS.
THEREFORE...06Z GFS AND THE 00Z GFS ENSEMBLE WAS USED PREDOMINATELY.

COLD FRONT SLOWS DOWN ON MONDAY AS IT CROSSES SOUTHEAST LOWER
MICHIGAN AND THE LEAD SHORTWAVE MOVES INTO ONTARIO AND QUEBEC.
HOWEVER...ADDITIONAL SHORTWAVE ENERGY WILL SLIDE FROM THE NORTHERN
GREAT PLAINS TO THE GREAT LAKES DURING THE AFTERNOON AND MONDAY NIGHT.
BETTER MOISTURE WILL RESIDE ON THE SOUTHERN FLANK OF THIS SECOND
SHORTWAVE CLOSER TO THE SURFACE BOUNDARY IN VICINITY OF UPPER LEVEL
-DIVQ AND MID-LEVEL CONVERGENCE.  ALTHOUGH ITS POSSIBLE THAT ALL
AREAS COULD RECEIVE RAIN...WILL ADJUST TO SHOW HIGHER PRECIP CHANCES
TO THE SOUTH.  MOST OF THE PRECIP LOOKS TO BE DONE BY TUESDAY
MORNING...WHEN HIGH PRESSURE BUILDS INTO THE GREAT LAKES.
HOWEVER...MODELS INDICATE 850MB TEMPS FALLING TO BETWEEN +1 AND +3C
WITH THERMAL TROUGHING OVERHEAD.  DEPENDING ON HOW DRY THE AIRMASS
IS BEHIND THE FRONT...COULD WE BE LOOKING AT THE FIRST LAKE EFFECT
RAIN EVENT OF THE SEASON?  REGARDLESS...WILL DEFINITELY SIDE WITH
MOSTLY CLOUDY-CLOUDY FORECAST.  TEMPERATURES MODERATE HEADING INTO
WEDNESDAY AS THE SURFACE HIGH SHIFTS EAST AND WINDS TURN MORE
SOUTHERLY.  SHORTWAVE ENERGY CROSSING THE PLAINS WILL THEN HELP LIFT
A WARM FRONT INTO THE AREA ON THURSDAY AND SHIFT A COLD FRONT ACROSS
MICHIGAN ON FRIDAY WITH PRECIP CHANCES RETURNING.

MPC

&&

.MARINE.../ISSUED AT 833 PM/

DECIDED TO AX THE SMALL CRAFT EARLIER THIS EVENING AS GRADIENT
CONTINUES TO RELAX AND REGIONAL OBS SHOW GUSTS UNDER 20 KNOTS NOW
(MOST UNDER 15 KNOTS). NO OTHER CONCERNS THRU THE NIGHT.

LAWRENCE

&&

.AVIATION.../ISSUED 125 AM /OVERALL...VFR CONDITIONS EXPECTED THRU
THE TAF PERIOD. INITIAL CONCERN WILL BE PATCHY FOG GIVEN RECENT RAIN
AND INITIALLY CLEAR SKIES (OUTSIDE OF SOME HIGH CLOUDS) WITH CALM
WINDS. KAPN/KPLN STAND TO SEE THE BEST SHOT AT FOG...WITH PERIODIC
IFR CONDITIONS POSSIBLE. OUTSIDE OF THAT...JUST SOME INCREASE IN MID
CLOUD FROM WEST TO EAST THRU SUNRISE...GIVING WAY TO LOWER CEILINGS
(4-5KFT) THRU THE MORNING AND EARLY AFTERNOON HOURS IN ADVANCE OF AN
APPROACHING WEAK SURFACE TROUGH. WILL LIKELY SEE SCATTERED SHOWERS
MAKE A RUN TOWARD KPLN BEFORE SUNRISE...WITH CHANCES EXTENDING
TOWARD KAPN INTO EARLY AFTERNOON. IMPROVING CONDITIONS THEN
ANTICIPATED BY LATE AFTERNOON/EARLY EVENING WITH THE ARRIVAL OF WEAK
HIGH PRESSURE.

LAWRENCE


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.

&&

$$

000
FXUS63 KDTX 060503
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
103 AM EDT SAT SEP 6 2008

.AVIATION...

THE 00Z DTX SOUNDING SHOWED A STRONG INVERSION BASED NEAR 4500 FT
WITH A SHALLOW LAYER OF MOISTURE UNDER THIS INVERSION. RECENT
SATELLITE TRENDS INDICATE THAT THE STRATUS FIELD HAS BEEN EXPANDING
UNDERNEATH THIS INVERSION. EXPECT THE VFR STRATUS DECK WILL PERSIST
THROUGH MOST OF THE MORNING UNTIL DAYTIME HEATING ALLOWS THE CLOUDS
TO LIFT INTO A SCATTERED CU FIELD AROUND 15Z. THERE HAVE BEEN SOME
MVFR STRATO CU REPORTED AROUND PHN AS A RESULT OF THE MOISTURE FLUX
OFF LAKE HURON. THE LOW LEVEL FLOW IS FORECAST TO VEER SLIGHTLY MORE
NORTH-NORTHEASTERLY THROUGH THE MORNING...WHICH MAY BRING SOME OF
THESE LOWER CLOUDS INTO THE DETROIT AREA AROUND DAYBREAK. MBS HAS
BEEN RIGHT ON THE EDGE OF THE CLOUDS. WEAK LOW LEVEL DRY AIR
ADVECTION UNDER NORTHERLY FLOW SHOULD STILL PROVIDE AN OVERALL
CLEARING TREND AT MBS DURING THE MORNING...WHICH WOULD PROVIDE SOME
OPPORTUNITY FOR RADIATIONAL FOG DEVELOPMENT AROUND DAYBREAK. HAVE
THUS INTRODUCED SOME MVFR VSBY RESTRICTIONS AT MBS TO ACCOUNT FOR
THIS.

&&

.PREV DISCUSSION...ISSUED 1021 PM EDT FRI SEP 5 2008

UPDATE...

THE 00Z DTX SOUNDING SHOWED A MUCH STRONGER INVERSION BASED NEAR
850MB THAN INDICATED BY MODEL SOUNDINGS. EVEN THOUGH THE MOIST
LAYER IS SOMEWHAT SHALLOW...THE STRENGTH OF THE INVERSION SHOULD
KEEP THIS MOISTURE TRAPPED. SATELLITE TRENDS OVER THE LAST HOUR
HAVE BEEN SHOWING AN INCREASE IN THE CLOUD COVER. NORTHERLY FLOW
AND SHALLOW INSTABILITY OFF LAKE HURON SHOULD ADD SOME LAKE
CONTRIBUTION TO THE CLOUDS AS WELL. SO WILL UPDATE TO INCREASE
CLOUD COVER A BIT. NORTHERLY DOWNSLOPE FLOW SHOULD STILL ALLOW
SOME SIGNIFICANT BREAKS ACROSS THE SAGINAW VALLEY AND POSSIBLY
MONROE AND WAYNE COUNTIES. WITH MORE CLOUDS EXPECTED...HAVE
INCREASED MIN TEMPS A COUPLE DEGREES. WILL ALSO REMOVE MENTION OF
FOG WITH THE EXCEPTION OF THE SAGINAW VALLEY WERE SIGNIFICANT
PERIODS OF CLEARING MAY STILL PROMOTE RADIATIONAL FOG DEVELOPMENT.

PREV DISCUSSION...ISSUED 401 PM EDT FRI SEP 5 2008

SHORT TERM...TONIGHT

LOW PRESSURE THAT BROUGHT A COLD FRONT THROUGH THE AREA EARLY THIS
MORNING WILL CONTINUE TO TRACK NORTHEAST ACROSS QUEBEC TONIGHT. A
FEW SPRINKLES ARE SHOWING UP ON AREA RADARS OUT OF THE DENSE
STRATOCU DECK THAT REMAINS OVER SOUTHEAST MICHIGAN. THIS DECK IS
CLEARING FROM THE NORTHWEST WITH NORTHERN PORTIONS OF THE CWA
EXPECTED TO SEE MOSTLY CLEAR SKIES DEVELOP LATE THIS
EVENING. MEANWHILE A LINGERING THERMAL TROUGH EXTENDING
BACK FROM THE SURFACE LOW ACROSS LAKE HURON AND LAKE ERIE WILL HELP
THE CLOUDS PERSIST THROUGH THE NIGHT IN OUR SOUTHERN AND EASTERN
COUNTIES. DESPITE AN OVERALL DRYING TREND IN DEWPOINTS...NORTHERLY
WINDS OFF LAKE HURON WILL CONTINUE TO ADD MOISTURE TO THE BOUNDARY
LAYER MAKING PATCHY FOG A CONCERN FOR AREAS NEAR THE LAKES TONIGHT.
GUIDANCE NUMBERS LOOKED REASONABLE IN THE NORTH WHERE SKIES SHOULD
BE MOSTLY CLEAR BUT HAVE GONE A FEW DEGREES ABOVE GUIDANCE IN
THE SOUTH WHERE CLOUDS SHOULD HANG ON OVERNIGHT.

LONG TERM...SATURDAY THROUGH NEXT FRIDAY

UPPER SHORTWAVE SPINNING OVER KS/NE WILL LIFT NORTHEAST AND ACROSS
LOWER MICHIGAN EARLY TOMORROW...JUST AHEAD OF AN APPROACHING WEAK
SURFACE TROUGH THAT IS CURRENTLY PUSHING INTO NORTHERN MINNESOTA.
THIS TROUGH WILL THEN LIFT ACROSS NORTHERN LAKE HURON TOMORROW
EVENING. WATER VAPOR IMAGERY INDICATES THIS SHORTWAVE MAY BE A
LITTLE STRONGER THAN MODELS SUGGEST. WITH MODELS STREAMING SOME
MOISTURE IN AHEAD OF THESE FEATURE TOMORROW...AND GUIDANCE EVEN
KICKING OUT SOME POPS...WILL ADD A MENTION OF SHOWERS UP AROUND THE
TRI-CITIES FOR TOMORROW AFTERNOON. OTHERWISE...JUST EXPECT
INCREASING CLOUDS FOR THE REMAINDER OF SOUTHEAST MICHIGAN TOWARDS
AFTERNOON AND EVENING AS THESE FEATURES PASS TO OUR NORTH.
TEMPERATURES ARE EXPECTED TO REBOUND BACK UP INTO THE 70S TOMORROW.

BROAD UPPER TROUGHING WILL SET UP ACROSS MUCH OF THE NORTHERN U.S.
SATURDAY NIGHT...USHERING IN A PERIOD OF FAST ENERGETIC WESTERLY
FLOW THAT WILL HOLD OVER THE GREAT LAKES INTO TUESDAY. INDIVIDUAL
WAVES THAT WILL EJECT THROUGH THIS FLOW WILL BE HARD TO TIME...BUT
LARGER WAVES ARE STILL EXPECTED TO PUSH THROUGH ON SUNDAY AND
MONDAY. NAM/GFS IN GOOD AGREEMENT WITH A WEAK WARM FRONT LIFTING UP
THROUGH SOUTHERN LOWER MICHIGAN SUNDAY MORNING...AND INTO CENTRAL
LOWER MICHIGAN BY LATE AFTERNOON. NAM SHOWS GREAT MOIST ISENTROPIC
ASCENT OCCURING EARLY OVER THE SOUTHERN PORTION OF THE FORECAST
AREA...THEN LIFTING SLOWLY NORTHWARD THROUGHOUT THE DAY. GFS DIFFERS
SLIGHTLY AND KEEPS STRONGER ASCENT LIMITED TO THE TRI-CITIES AND
THUMB. WILL HOLD ONTO CHANCE POPS THROUGHOUT THE DAY...WITH THE
EXPECTATION OF SEEING MORE ACTIVITY ALONG AND NORTH OF I-69...AT
LEAST UNTIL MODELS COME INTO BETTER AGREEMENT. PRECIPITATION SHOULD
BE FAIRLY LIGHT. BETTER CHANCE OF PRECIPITATION WILL OCCUR LATE
SUNDAY NIGHT AND MONDAY AS THE STRONGEST OF THE UPPER WAVES MOVES
THROUGH MICHIGAN AND PUSHES A COLD FRONT THROUGH THE REGION.

COLDER AIR WILL CONTINUE TO SPILL INTO THE REGION ON TUESDAY AS THE
FRONT EXITS AND A COOL DOME OF HIGH PRESSURE SETTLES IN OVERHEAD.
CONDITIONS WILL TURN QUITE FALL-LIKE ON TUESDAY AS H850 TEMPS COOL
TO AROUND 5 DEGREES C. THIS SHOULD PROVIDE SURFACE TEMPERATURES THAT
STRUGGLE TO REACH EVEN THE UPPER 60S...WITH OVERNIGHT LOWS THEN
DROPPING INTO THE 40S JUST ABOUT EVERYWHERE. SOME CONCERN FOR
STRATUS DEVELOPMENT TUESDAY BEHIND THE FRONT AS COOL AIR STREAMS
OVER THE VERY WARM LAKES. THE ADDITIONAL CLOUD COVER WOULD HAVE AN
EFFECT ON TEMPERATURES...AND FORECAST WILL NEED TO BE AJUSTED IF
THIS SCENARIO STARTS TO LOOK MORE FAVORABLE

HIGH PRESSURE STILL EXPECTED TO HOLD OVER THE REGION INTO WEDNESDAY
BEFORE SOUTHERLY FLOW STARTS TO INCREASE AHEAD OF THE NEXT UPPER
TROUGH. MEDIUM RANGE MODELS ARE STARTING TO STRUGGLE WITH HOW THEY
HANDLE MID-WEEK UPSTREAM ENERGY OVER THE PACIFIC NORTHWEST. HAVE A
HIGH DEGREE OF CONFIDENCE WITH THE TROUGH ARRIVING TOWARDS THE END
OF THE WEEK...BUT LOW CONFIDENCE WITH DETAILS...AMPLITUDE...AND
EXACT TIMING.

MARINE...

THE PRESSURE GRADIENT WILL CONTINUE TO WEAKEN INTO SATURDAY AS THE
LOW PRESSURE SYSTEM THAT MOVED THROUGH THE AREA LAST NIGHT CONTINUES
NORTHEAST ACROSS QUEBEC. SUSTAINED WINDS WILL REMAIN AROUND 20 KNOTS
ACROSS NORTHERN LAKE HURON WHILE OTHER AREAS HAVE ALREADY STARTED TO
SUBSIDE. SMALL CRAFT ADVISORIES HAVE BEEN EXTENDED OVERNIGHT FOR THE
OUTER SAGINAW BAY AND INTO SATURDAY ON NEARSHORE AREAS FROM PORT
AUSTIN TO PORT SANILAC AS WAVES WILL REMAIN HIGH UNDER NORTHERLY
WINDS.

CONDITIONS WILL BECOME MORE FAVORABLE FOR BOATING FROM SATURDAY
AFTERNOON INTO SUNDAY AS HIGH PRESSURE BUILDS EASTWARD ACROSS THE
GREAT LAKES REGION. ANOTHER LOW PRESSURE SYSTEM WILL BRING THE NEXT
COLD FRONT THROUGH THE REGION ON MONDAY...POTENTIALLY CREATING MORE
UNSTABLE CONDITIONS AS MUCH COOLER AIR FILTERS ACROSS THE WARMER
LAKE WATERS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 4 AM SATURDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO HARBOR
     BEACH...UNTIL 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
     SANILAC...UNTIL 4 PM SATURDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....SC
UPDATE.......SC
SHORT TERM...KEC
LONG TERM....HLO
MARINE.......KEC

YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

000
FXUS63 KGRR 060451
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1250 AM EDT SAT SEP 6 2008

LATEST UPDATE...AVIATION...

.SYNOPSIS...(400 PM EDT FRI SEP 5 2008)
AN UPPER LEVEL TROUGH OF LOW PRESSURE COVERING THE MID SECTION OF
THE NATION WILL RESULT IN A SOMEWHAT UNSETTLED WEATHER PATTERN
THROUGH EARLY NEXT WEEK. DISTURBANCES PASSING THROUGH THIS UPPER
TROUGH WILL LEAD TO PERIODIC EPISODES OF SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS. HOWEVER PRECIPITATION