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000
FXUS65 KTFX 110515
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1115 PM MDT FRI OCT 10 2008
...UPDATE TO AVIATION...
.DISCUSSION...
UPDATE FORTHCOMING. HAVE MADE MINOR ADJUSTMENTS TO THE POP AND SKY
CONDITION GRIDS...MAINLY TO ALIGN WITH NEIGHBORING OFFICES. WILL
CONTINUE WITH WINTER WEATHER HIGHLIGHT THOUGH MODELS NOW INDICATE
GREATEST IMPACT WILL BE TO THE EAST AND SOUTH OF GREAT FALLS.
REMAINDER OF FORECAST LOOKS ON TRACK. EMANUEL
&&
.AVIATION...
UPDATED 0515Z.
A DEEP UPPER LEVEL TROUGH OF LOW PRESSURE WILL REMAIN OVER WESTERN
AND CENTRAL MONTANA AT LEAST THROUGH SATURDAY EVENING WITH THE UPPER
LOW PRESSURE CENTER SOUTH OF THE AREA OVER THE GREAT BASIN AND
CENTRAL ROCKIES. THE RESULTING MOIST EASTERLY UPSLOPE FLOW OVER THE
AREA WILL CONTINUE THE WIDESPREAD CLOUDINESS AND OCCASIONAL SNOW.
CONDITIONS WILL MOSTLY BE LOW VFR/HIGH MVFR ACROSS SOUTHWEST (KBZN
AND KHLN TERMINALS) AND CENTRAL (KLWT AND KGTF) MONTANA. SOME
HEAVIER SHOWERS ACROSS THESE AREAS MAY CAUSE OCCASIONAL IFR
CONDITIONS...MAINLY OVERNIGHT. CLOUDS AND SNOW WILL BE A BIT MORE
SCARCE ACROSS NORTH CENTRAL MONTANA (KCTB AND KHVR)...FOR MOSTLY VFR
CONDITIONS THERE. HOWEVER...A FEW SHOWERS MAY CAUSE BRIEF MVFR
CONDITIONS AT KHVR OVERNIGHT. ALSO...MORE WIDESPREAD MVFR CEILINGS
WITH PATCHY FOG WILL DEVELOP AT KCTB BETWEEN 09Z AND 15Z. WINDS WILL
MOSTLY BE BREEZY AND NORTHEASTERLY...WITH WINDS INCREASING DURING
THE DAY ON SATURDAY. COULSTON
&&
.PREV DISCUSSION...ISSUED 259 PM MDT FRI OCT 10 2008
TONIGHT THROUGH SUNDAY...EARLY SEASON WINTER STORM WILL CONTINUE
TO IMPACT SOUTHWEST MONTANA AND SOUTHERN PORTIONS OF CENTRAL
MONTANA. HOWEVER...MOST OF NORTH CENTRAL MONTANA REMAINS BENEATH
PARTLY CLOUDY TO MOSTLY CLOUDY SKIES WITH ONLY A SLIGHT CHANCE TO
CHANCE OF SNOW EXPECTED DURING THE SHORT TERM PERIOD. THE DEEP
UPPER LEVEL LOW WILL CONTINUE TO SPIN OVER THE GREAT BASIN THROUGH
SATURDAY THEN WILL FINALLY BEGIN TO LIFT OUT TO THE NORTHEAST
SATURDAY NIGHT AND SUNDAY. AS THE LOW LIFTS OUT...PRECIPITATION
WILL BEGIN TO TAPER OFF IN SOUTHWEST MONTANA. AT THE SAME TIME A
COMBINATION OF STRONG UPPER LEVEL FORCING AND LOW LEVEL
FRONTOGENESIS WILL CAUSE A SIGNIFICANT BAND OF PRECIPITATION
ACROSS EASTERN PORTIONS OF MY CWA. HAVE OPTED TO ADD BLAINE COUNTY
TO THE WINTER STORM WARNING FOR THE PERIOD OF SATURDAY NIGHT
THROUGH EARLY MONDAY MORNING...AND HAVE ALSO EXTENDED FERGUS
COUNTY OUT OVERNIGHT ON SUNDAY AS WELL. MPJ
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 34 22 35 / 30 40 50 30
CTB 21 35 19 40 / 20 20 20 10
HLN 29 36 27 37 / 60 60 50 50
BZN 26 37 25 34 / 80 80 80 70
WEY 19 30 18 27 / 90 80 90 60
DLN 21 30 18 31 / 90 70 80 50
HVR 24 41 21 38 / 20 20 20 30
LWT 23 31 19 29 / 70 80 80 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING CONTINUES UNTIL 6 PM MDT SUNDAY FOR
MTZ008-012-014-015-050-052>055.
WINTER STORM WARNING CONTINUES UNTIL 6 AM MDT MONDAY FOR MTZ051.
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 AM MDT MONDAY FOR
MTZ047.
&&
$$
SHORT TERM...EMANUEL/MPJ
LONG TERM...ZELZER/SAUCIER
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KTFX 110322
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
900 PM MDT FRI OCT 10 2008
.DISCUSSION...
UPDATE FORTHCOMING. HAVE MADE MINOR ADJUSTMENTS TO THE POP AND SKY
CONDITION GRIDS...MAINLY TO ALIGN WITH NEIGHBORING OFFICES. WILL
CONTINUE WITH WINTER WEATHER HIGHLIGHT THOUGH MODELS NOW INDICATE
GREATEST IMPACT WILL BE TO THE EAST AND SOUTH OF GREAT FALLS.
REMAINDER OF FORECAST LOOKS ON TRACK. EMANUEL
&&
.AVIATION...
UPDATED 0040Z.
A DEEP UPPER LEVEL TROUGH OF LOW PRESSURE WILL REMAIN OVER WESTERN
AND CENTRAL MONTANA AT LEAST THROUGH SATURDAY WITH THE UPPER LOW
PRESSURE CENTER SOUTH OF THE AREA OVER THE GREAT BASIN AND CENTRAL
ROCKIES. THE RESULTING MOIST EASTERLY UPSLOPE FLOW OVER THE AREA
WILL CONTINUE THE WIDESPREAD CLOUDINESS AND OCCASIONAL SNOW.
CONDITIONS WILL MOSTLY BE LOW VFR/HIGH MVFR ACROSS SOUTHWEST (KBZN
AND KHLN TERMINALS) AND CENTRAL (KLWT AND KGTF) MONTANA. SOME
HEAVIER SHOWERS ACROSS THESE AREAS MAY CAUSE OCCASIONAL IFR
CONDITIONS...MAINLY OVERNIGHT. CLOUDS AND SNOW WILL BE A BIT MORE
SCARCE ACROSS NORTH CENTRAL MONTANA (KCTB AND KHVR)...FOR MOSTLY VFR
CONDITIONS THERE. HOWEVER...A FEW SHOWERS MAY CAUSE BRIEF MVFR
CONDITIONS AT KHVR THROUGH 06Z...AND MORE WIDESPREAD MVFR CEILINGS
WILL DEVELOP DURING THE OVERNIGHT HOURS AT KCTB. WINDS WILL MOSTLY
BE BREEZY AND NORTHEASTERLY...WITH WINDS INCREASING DURING THE DAY
ON SATURDAY. COULSTON
&&
.PREV DISCUSSION...ISSUED 259 PM MDT FRI OCT 10 2008
TONIGHT THROUGH SUNDAY...EARLY SEASON WINTER STORM WILL CONTINUE
TO IMPACT SOUTHWEST MONTANA AND SOUTHERN PORTIONS OF CENTRAL
MONTANA. HOWEVER...MOST OF NORTH CENTRAL MONTANA REMAINS BENEATH
PARTLY CLOUDY TO MOSTLY CLOUDY SKIES WITH ONLY A SLIGHT CHANCE TO
CHANCE OF SNOW EXPECTED DURING THE SHORT TERM PERIOD. THE DEEP
UPPER LEVEL LOW WILL CONTINUE TO SPIN OVER THE GREAT BASIN THROUGH
SATURDAY THEN WILL FINALLY BEGIN TO LIFT OUT TO THE NORTHEAST
SATURDAY NIGHT AND SUNDAY. AS THE LOW LIFTS OUT...PRECIPITATION
WILL BEGIN TO TAPER OFF IN SOUTHWEST MONTANA. AT THE SAME TIME A
COMBINATION OF STRONG UPPER LEVEL FORCING AND LOW LEVEL
FRONTOGENESIS WILL CAUSE A SIGNIFICANT BAND OF PRECIPITATION
ACROSS EASTERN PORTIONS OF MY CWA. HAVE OPTED TO ADD BLAINE COUNTY
TO THE WINTER STORM WARNING FOR THE PERIOD OF SATURDAY NIGHT
THROUGH EARLY MONDAY MORNING...AND HAVE ALSO EXTENDED FERGUS
COUNTY OUT OVERNIGHT ON SUNDAY AS WELL. MPJ
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 34 22 35 / 30 40 50 30
CTB 21 35 19 40 / 20 20 20 10
HLN 29 36 27 37 / 60 60 50 50
BZN 26 37 25 34 / 80 80 80 70
WEY 19 30 18 27 / 90 80 90 60
DLN 21 30 18 31 / 90 70 80 50
HVR 24 41 21 38 / 20 20 20 30
LWT 23 31 19 29 / 70 80 80 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING CONTINUES UNTIL 6 PM MDT SUNDAY FOR
MTZ008-012-014-015-050-052>055.
WINTER STORM WARNING CONTINUES UNTIL 6 AM MDT MONDAY FOR MTZ051.
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 AM MDT MONDAY FOR
MTZ047.
&&
$$
SHORT TERM...EMANUEL/MPJ
LONG TERM...ZELZER/SAUCIER
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
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000
FXUS65 KGGW 110318
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
918 PM MDT FRI OCT 10 2008
...MAJOR WINTER-TYPE STORM EXPECTED SATURDAY NIGHT THROUGH MONDAY
MORNING...
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
ELONGATING UPPER LOW MOVING VERY SLOWLY WITH AN APPARENT CLOSED
CENTER IN W ID. NE MT IN STRONG SW FLOW ALOFT ASSOCIATED WITH
THIS...SOMEWHAT WARMER AND MOISTER THAN THE AIRMASS BELOW 700 MB.
LOWER LEVEL AIRMASS IS DRIER AND RELATIVELY COLDER. THIS
ASSOCIATED WITH A SURFACE HIGH EXTENDING FROM AB TO NUNAVUT. WEAK
SHORTWAVES IN THE STRONG FLOW ALOFT AFFECTING OUR AREA...WITH A
STRONGER SHORTWAVE TO ARRIVE LATE TONIGHT. THIS SEEN WELL ON
SATELLITE CHANNELS IN W WY MOVING NE INTO SC MT WITH COOLING CLOUD
TOPS.
PHONE CALLS HAVE SHOWN LIGHT PRECIP HAS SPREAD INTO PORTIONS OF
OUR N...AS FAR N AS PWD. 88D REFLECTIVITY INDICATES SUCH AS WELL.
WILL UPDATE TO EXPAND AND INCREASE POPS. PRECIP MAINLY AS LIGHT
RAIN THIS EVE WITH MANY LOCATIONS STILL AROUND 40F OR SO. MODELS
INDICATE CONTINUED COLD ADVECTION TONIGHT WITH 850 MB TEMPS
DROPPING TO MINUS 2-4C IN OUR AREA BY MORN. THIS SHOULD TURN MOST
PRECIP TO LIGHT SNOW WITH SOME AREAS HAVING LIGHT ACCUMS BY MORN.
SIMONSEN
PREVIOUS SHORT TERM...FOR NORTHEAST MONTANA...TOINGHT
THROUGH SUNDAY...CURRENT GOES WATER VAPOR IMAGERY REVEALS A
DEEPENING UPPER LEVEL TROUGH OVER THE GREAT BASIN. AT THE
SURFACE...A LOW PRESSURE SYSTEM IS DEVELOPING OVER COLORADO AND A
CANADIAN HIGH PRESSURE SYSTEM IS SITUATED OVER ALBERTA. AN UPPER
JET STREAK IS PASSING ABOVE EASTERN MONTANA THIS AFTERNOON...WHICH
HAS RESULTED IN LIGHT RAIN AND HIGH ELEVATION SNOW SOUTH OF THE
MISSOURI RIVER. THIS PATTERN WILL PERSIST THROUGH SATURDAY MORNING
AS THE UPPER JET STREAK STRENGTHENS IN THE ENTRANCE REGION.
BY SATURDAY AFTERNOON A JET STREAK ROUNDS THE BASE OF THE UPPER
TROUGH AND COUPLES WITH AFOREMENTIONED UPSTREAM WAVE. THE SURFACE
LOW ORGANIZES AND MOVES INTO CENTRAL SOUTH DAKOTA BY SUNDAY
MORNING WHILE THE SURFACE HIGH RETREATS TO THE EAST.
MEANWHILE...SUBTROPICAL MOISTURE WILL BE DRAWN NORTHWARD FROM THE
REMNANTS OF HURRICANE NORBERT. THIS WILL PRODUCE HEAVY SNOW ACROSS
NORTHEAST MONTANA SATURDAY NIGHT AND SUNDAY...WHICH HAS THE
POTENTIAL TO PERSIST LONGER AS MODELS DEVELOP A ROBUST TROWAL
SIGNATURE OVER MUCH OF THE AREA. THE DRY SLOT IS FORECAST TO MOVE
FROM SOUTHEAST MONTANA INTO WESTERN NORTH DAKOTA...BUT A SLIGHT
SHIFT IN TRACK COULD LEAD TO A QUICKER END OF THE SNOW IN THE
EASTERN ZONES.
6 TO 12 INCHES WITH LOCALLY HIGHER AMOUNTS IS A REASONABLE
ACCUMULATION FORECAST AT THIS POINT. MODEL QPF AMOUNTS SUGGEST
HIGHER. HOWEVER...SNOW WILL HAVE SOME TROUBLE ACCUMULATING
INITIALLY AS THE SURFACE AND SUBSURFACE REMAIN WARM GIVEN THE TIME
OF YEAR. A MODERATELY STRONG NORTH WIND WILL DEVELOP...WHICH HAS
THE POTENTIAL TO PRODUCE BLOWING AND DRIFTING.
TEMPERATURES WILL FALL INTO THE LOW 30S AT THE ONSET OF THE STORM
SYSTEM AND REMAIN IN THAT VICINITY THROUGH THE PERIOD. AJZ
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
ALL CHANGES WERE CONTAINED TO THE EARLY PART OF THE PERIOD TO HELP
HANDLE THE ONGOING MAJOR WINTER STORM. BIGGEST CHANGE INVOLVED THE NEW
RUNS OF THE DGEX...GFS...AND NAM WHICH ARE ALL CONSISTENT WITH A
SLOWER EXIT OF THE UPPER LOW. THE GFS ENSEMBLES ALSO HEAVILY FAVOR
A SLOWER SOLUTION. THE OUTLIER CONTINUES TO BE THE ECMWF. IT TAKES
THE LOW OUT OF EASTERN MONTANA ON SUNDAY AFTERNOON AND MOVES IT TO
HUDSON BAY CANADA BY MONDAY AFTERNOON...SOME 800 MILES IN 24
HOURS. GIVEN THE BETTER CONSENSUS IN A SLOWER SOLUTION RAMPED UP
POPS TO COVER THE LINGERING EFFECTS OF THE LOW ACROSS NORTHEAST
MONTANA. DUE TO THIS CHANGE THE WINTER STORM WARNING WILL BE
PUSHED INTO SUNDAY NIGHT. GILCHRIST
PREVIOUS LONG TERM DISCUSSION...STORM VORTEX WILL BEGIN LIFTING
OUT OF NORTHEAST MONTANA SUNDAY NIGHT. WRAP-AROUND ENERGY FROM THE
NORTHERLY FLOW ON THE WEST SIDE OF THE LOW WILL FOCUS QPF OVER THE
NORTHERN ZONES FOR ADDITIONAL TAPERING OFF SNOWFALL. RISING
HEIGHTS FROM THE WEST MONDAY WILL CUT OFF ANY REMAINING
PRECIPITATION. THE POSITIVE LEANING RIDGE WILL BE QUICKLY
FLATTENED BY A QUICK-MOVING SHORTWAVE ACROSS ALBERTA AND
SASKATCHEWAN MONDAY NIGHT. THE 00Z GFS SHORTWAVE IS MORE SHALLOW
THAN THE 12/00Z ECMWF SHORTWAVE. TUESDAY AND WEDNESDAY THE MODELS
SEND ADDITIONAL WEAK SHORTWAVES ACROSS CANADA...NOT NECESSARILY IN
AGREEMENT WITH EACH OTHER. BUT AROUND WEDNESDAY NIGHT OR THURSDAY
AN UPPER RIDGE SLOWLY BUILDS UP OVER THE WEST...MAINTAINING UPPER
FLOW FROM THE NORTHWEST LOCALLY. AFTER THE PASSAGE OF THE SUNDAY
NIGHT STORM THE CONDITIONS WILL GENERALLY DRY AND COOL...WITH THE
POSSIBILITY OF WARMING TO NORMAL BY THE END OF THE PERIOD. SCT
&&
.AVIATION...
MOST OF THE PRECIPITATION TONIGHT HAS BEEN SUPPRESSED TO THE
SOUTHERN PORTION OF THE STATE WITH LIGHT MIXED PRECIPITATION IN
CENTRAL AREAS AND DRY CONDITIONS TO THE NORTH. OCCASIONAL IFR
CEILINGS ARE EXPECTED TO CONTINUE FOR A FEW MORE HOURS AT
GLENDIVE...POSSIBLY LIFTING TO MVFR/VFR LATER TONIGHT.
VFR CONDITIONS ARE EXPECTED INTO SATURDAY AT THE OTHER 3
TERMINALS.
ALL TERMINALS WILL CONTINUE TO SEE NORTHEAST WINDS AROUND 10 KTS
TONIGHT...INCREASING TO 15-20 KTS BY SATURDAY AFTERNOON.
A MAJOR WINTER STORM SYSTEM IS SET TO IMPACT NORTHEAST MONTANA
SUNDAY NIGHT INTO MONDAY NIGHT. EXPECT WIDESPREAD IFR CEILINGS AND
VISIBILITIES DURING THIS TIME...ALONG WITH GUSTY NORTH WINDS AT
15 TO 25 KTS. GILCHRIST/JAMBA
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 AM MDT MONDAY FOR
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-NORTHERN PHILLIPS-SOUTHWEST
PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT.
WINTER STORM WARNING FROM 12 PM SATURDAY TO 6 AM MDT MONDAY FOR
PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-WIBAUX.
&&
$$
WEATHER.GOV/GLASGOW
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000
FXUS65 KBYZ 110259
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
859 PM MDT FRI OCT 10 2008
.SHORT TERM...VALID FOR SAT AND SUN...
NO UPDATES PLANNED TO THE FORECAST TONIGHT. SNOW CONTINUES OVER
MUCH OF THE FORECAST AREA THIS EVENING...WITH A BIT OF RAIN MIXED
WITH SNOW OVER NORTHEAST ZONES. JET MAX SUPPORTING A STRONG
DISTURBANCE CAUSING A COOLING OF CLOUD TOPS OVER WESTERN WYOMING.
EXPECT THIS ENERGY MOVE INTO THE AREA AND TO COMBINE WITH LOW
LEVEL ISENTROPIC FORCING AND STRONG DIFFLUENCE ALOFT TO INCREASE
PRECIPITATION RATES BY MIDNIGHT WEST...THEN SPREAD NORTH AND EAST
LATE TONIGHT. SNOW REPORTS CONTINUE TO BE HEAVY COMING OUT OF
WESTERN FOOTHILLS AREAS AS STRONG UPSLOPE FLOW COMBINES WITH
DIFFLUENT FLOW ALOFT TO KEEP ENHANCED SNOW GROWTH REGIME IN PLACE.
REPORTS FROM EARLY EVENING INDICATED AROUND 16 INCHES FROM MCLEOD
TO NYE TO RED LODGE. EASTERN ZONES STRUGGLING TO PICK UP SNOW IN
MANY LOCATIONS. WAS TEMPTED TO CHANGE THE WARNING IN THESE
AREAS...BUT SOUNDINGS AND CROSS SECTIONS SUPPORT MODERATE TO HEAVY
SNOW AT ELEVATIONS ABOVE ABOUT 3400 FEET IN THE EAST TONIGHT. THIS
WOULD IMPACT AREAS OF SOUTHERN CUSTER AND FALLON COUNTY...AND MUCH
OF POWDER RIVER AND CARTER COUNTIES. WILL STILL STRUGGLE TO PICK
UP SNOW TONIGHT INTO EARLY TOMORROW IN THE RIVER VALLEY LOCATIONS
IN THESE COUNTIES THOUGH...BUT BY TOMORROW AFTERNOON STRONGER
SUPPORT FOR HEAVY SNOWFALL AT THE LOWER ELEVATIONS MOVES INTO THE
AREA. WILL ADJUST THE WARNING WORDING FOR THOSE ZONES TO REFLECT
THIS THINKING.
ROAD CONDITIONS SHOULD CONTINUE TO DETERIORATE OVERNIGHT
TONIGHT...ESPECIALLY WEST OF A MILES CITY TO BROADUS LINE.
TEMPERATURES ARE AT OR BELOW FREEZING NOW AND ROAD SURFACE
TEMPERATURES ARE INDICATING 32 OR 33 DEGREES AT 8 PM. BRIDGES AND
OVERPASSES WILL BE THE FIRST PLACES TO ICE UP SO USE CAUTION
DRIVING ACROSS THE REGION TONIGHT. CHAMBERS
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
UPPER LEVEL LOW PRESSURE EXITING THE REGION ON MONDAY BUT A CHANCE
FOR WRAP AROUND PRECIPITATION INTO THE AREA STILL EXISTS DURING
THE DAY...ESPECIALLY THE MORNING HOURS. NAM AND ECMWF ARE IN
AGREEMENT WITH TRYING TO PULL THE LOW FURTHER AWAY FROM THE AREA
WITH CURRENT TRENDS SHOWING THE WRF PULLING THE LOW FURTHER AWAY
THAN PREVIOUS RUNS. STILL THINK GIVEN IT STILL COULD BE WINTRY ON
MONDAY IS WORTH INTRODUCING IN THE FORECAST. STRONG NORTHWESTERLY
FLOW ALOFT REPLACES THE UPPER LOW ON TUESDAY AND ASSUMING THAT
SNOW COVER SHOULD BE SOLID ENOUGH TO HAVE A DRAMATIC IMPACT ON
TEMPERATURES DESPITE SUNSHINE. WEDNESDAY AND THURSDAY SHOULD STAY
COOL AS WEAK RIDGING BUILDS WEST OF THE AREA AND KEEPS SURFACE
HIGH PRESSURE AND WEAK MIXING IN PLACE. TEMPERATURES WILL HAVE TO
WATCHED CLOSELY AND ADJUSTED DOWNWARD IF SNOWFALL AMOUNTS END UP
AS WIDESPREAD AS EXPECTED. PROGRESSION OF RIDGE INTO THE AREA ON
FRIDAY GIVES A BETTER CHANCE FOR WARMING AND MORE FLOW OVER THE
CANADIAN ROCKIES MAY FAVOR A BETTER DOWNSLOPE PATTERN DEVELOPING.
HOWEVER...GREAT BASIN SURFACE HIGH PRESSURES MAY NOT BE THAT
SIGNIFICANT SO GAP FLOW WINDS MAY NOT BE AS STRONG AS NORMAL.
BORSUM
&&
.AVIATION...
SNOW...HEAVY AT TIMES...WILL CONTINUE TONIGHT AND THROUGH THE DAY
SATURDAY. LOCATIONS FROM KMLS EAST AND SOUTH THAT ARE CURRENTLY
EXPERIENCING RAIN WILL CHANGE TO SNOW LATER TONIGHT. SIGNIFICANT
SNOW ACCUMULATIONS WILL BE LIKELY THROUGH AT LEAST SATURDAY
NIGHT. EXPECT LOW CEILINGS AND VISIBILITIES THROUGHOUT THE PERIOD
WITH IFR AND LIFR CONDITIONS PREVAILING...ESPECIALLY LATER
TONIGHT AND DURING THE DAY SATURDAY.
FOR KBIL...EXPECT LIFR CONDITIONS TO BE PREDOMINANT THROUGH MUCH
OF THE NIGHT WITH SOME PERIODS OF VLIFR CONDITIONS. IMPROVEMENT
TO IFR LEVELS IS NOT LIKELY UNTIL POSSIBLY MID MORNING SATURDAY.
HOWEVER...ANOTHER ROUND OF HEAVIER SNOW IS LIKELY SATURDAY
AFTERNOON AND EVENING BRINGING THE POSSIBILITY OF VLIFR
CONDITIONS ONCE AGAIN. HOOLEY
&&
.PRELIMINARY POINT TEMP/POPS...
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 028/033 026/033 023/035 027/050 032/053 033/054 035/060
++/S +8/S 47/S 10/B 11/B 11/B 11/B
LVM 021/032 017/034 022/041 026/050 032/053 033/054 035/059
++/S +8/S 35/S 10/B 11/B 21/B 11/B
HDN 027/034 027/037 022/038 026/051 031/054 032/055 034/062
++/S +9/S 56/S 10/B 11/B 11/B 11/B
MLS 027/037 025/036 024/038 028/052 032/055 033/056 035/061
++/O +9/S 55/S 21/B 11/B 21/U 11/U
4BQ 026/035 026/035 023/038 027/052 030/055 031/056 033/061
++/S +9/S 53/S 10/U 11/U 21/B 11/U
BHK 024/035 023/035 022/040 023/050 029/053 031/054 034/059
++/O +9/S 54/S 11/B 11/B 21/B 11/B
SHR 023/034 023/034 022/037 026/050 029/053 031/054 033/060
++/S +9/S 35/S 10/U 11/U 12/W 21/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 28>42-56>58-63>68.
WY...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
[top]
000
FXUS65 KMSO 110257
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
857 PM MDT FRI OCT 10 2008
.UPDATE...CANCELLED WINTER WEATHER ADVISORY FOR THE SOUTHERN
SAPPHIRE MOUNTAINS AND LOST TRAIL PASS.
&&
.DISCUSSION...SNOWFALL HAS BECOME LIGHT ENOUGH TO CANCEL THE
ADVISORY FOR AREAS NEAR LOST TRAIL PASS. WINDS WILL STILL BE GUSTY
THROUGH THE NIGHT CAUSING SOME BLOWING SNOW IN THE AREA...BUT NEW
SNOWFALL WILL BE LIMITED. ANOTHER WAVE ROTATING AROUND THE LARGE
UPPER LEVEL LOW OVER IDAHO HAS MOVED INTO SOUTHWEST MONTANA AND
LEMHI COUNTY. ENHANCEMENT ON SATELLITE AND RADAR INDICATES THAT
SNOW WILL BE LIKELY IN THE HIGHER TERRAIN OF THESE AREAS WITH SOME
POSSIBLE IN THE VALLEYS AS THIS WAVE MOVES THROUGH TONIGHT. THIS
COMBINED WITH THE STRONG WINDS PRESENT IS ENOUGH TO CONTINUE THE ONGOING
ADVISORIES THROUGH THE NIGHT.
&&
.AVIATION...WIDESPREAD MOUNTAIN OBSCURATIONS IN CLOUDS AND SNOW
WILL PERSIST OVER NORTH CENTRAL IDAHO AND SOUTHWEST MONTANA
TONIGHT...AND LIKELY THROUGH THE WEEKEND. VALLEYS WILL
OCCASIONALLY SEE SNOW AND BLOWING SNOW RESULTING IN REDUCED
VISIBILITIES IN THESE SAME AREAS...BUT PERSISTENT IFR CONDITIONS
ARE NOT EXPECTED. NORTH TO NORTHEAST SURFACE WINDS WILL BE
WIDESPREAD THROUGH SATURDAY EVENING WITH TYPICAL SUSTAINED
VALUES PEAKING AROUND 20 KTS AND SOME GUSTS TO 30 KTS.
&&
.PREV DISCUSSION... /ISSUED 235 PM MDT FRI OCT 10 2008/
DISCUSSION...COOL AND MOIST UPPER TROUGH CONTINUES TO ROTATE AND
ELONGATE OVER THE NORTHWEST PORTION OF THE U.S. THE RESULT HAS
BEEN PERSISTENT LARGE SCALE LIFT OVER CENTRAL IDAHO AND SOUTHWEST
MONTANA. THE BEST COMBINATION OF LIFT AND AVAILABLE MOISTURE WAS
LAST NIGHT THROUGH MID MORNING. ACCUMULATING SNOW HAS DIMINISHED
ACROSS MOST AREAS SINCE THEN...BUT WITH THE ATMOSPHERIC ASCENT
EXPECTED THROUGH AT LEAST ANOTHER 24 HOURS...WILL KEEP A WINTER
HIGHLIGHT IN PLACE. HAVE DECIDED TO SCALE THE WARNINGS DOWN TO
WINTER WEATHER ADVISORIES TO COVER THE PERSISTENT LIGHT
ACCUMULATIONS. THESE ACCUMULATIONS COULD CONTINUE THROUGH SUNDAY
AFTERNOON WITH THE SLOW MOVING NATURE OF THE UPPER TROUGH.
HOWEVER...FOR NOW WILL ONLY MAINTAIN THE ADVISORY THROUGH SATURDAY
AFTERNOON AND SEE IF THE TROUGH CAN TRULY SUSTAIN THE LIFT.
THE NORTH TO NORTHEAST GRADIENT WILL ALSO CONTINUE TONIGHT AND
SATURDAY MAINTAINING BRISK SURFACE WINDS.
LATE SUNDAY NIGHT AND MONDAY THE TROUGH WILL MOVE EAST INTO THE
NORTHERN PLAINS ALLOWING A BRIEF DRY RIDGE TO DEVELOP. THIS WILL
HELP MODERATE TEMPERATURES. THIS RIDGING WILL NOT LAST LONG AS A
WESTERLY UPPER LEVEL FLOW PUSHES OVER THE NORTHERN STATES MIDWEEK.
THIS DOES NOT LOOK LIKE A VERY WET PATTERN BUT COULD PRODUCE SOME
SHOWERS OVER THE MOUNTAINS. BROAD RIDGING WILL AGAIN DRY THE
REGION OUT LATE IN THE COMING WEEK.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY UNTIL 6 PM MDT SATURDAY FOR
BUTTE/BLACKFOOT REGION.
ID...WINTER WEATHER ADVISORY UNTIL 6 PM MDT SATURDAY FOR EASTERN
LEMHI COUNTY.
&&
$$
UPDATE...LOEFFELBEIN
PREVIOUS DISCUSSION....WHITMORE/ALLEGRETTO
AVIATION...LOEFFELBEIN
000
FXUS65 KTFX 110039
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
640 PM MDT FRI OCT 10 2008
...UPDATE TO AVIATION...
.DISCUSSION...
TONIGHT THROUGH SUNDAY...EARLY SEASON WINTER STORM WILL CONTINUE
TO IMPACT SOUTHWEST MONTANA AND SOUTHERN PORTIONS OF CENTRAL
MONTANA. HOWEVER...MOST OF NORTH CENTRAL MONTANA REMAINS BENEATH
PARTLY CLOUDY TO MOSTLY CLOUDY SKIES WITH ONLY A SLIGHT CHANCE TO
CHANCE OF SNOW EXPECTED DURING THE SHORT TERM PERIOD. THE DEEP
UPPER LEVEL LOW WILL CONTINUE TO SPIN OVER THE GREAT BASIN THROUGH
SATURDAY THEN WILL FINALLY BEGIN TO LIFT OUT TO THE NORTHEAST
SATURDAY NIGHT AND SUNDAY. AS THE LOW LIFTS OUT...PRECIPITATION
WILL BEGIN TO TAPER OFF IN SOUTHWEST MONTANA. AT THE SAME TIME A
COMBINATION OF STRONG UPPER LEVEL FORCING AND LOW LEVEL
FRONTOGENESIS WILL CAUSE A SIGNIFICANT BAND OF PRECIPITATION
ACROSS EASTERN PORTIONS OF MY CWA. HAVE OPTED TO ADD BLAINE COUNTY
TO THE WINTER STORM WARNING FOR THE PERIOD OF SATURDAY NIGHT
THROUGH EARLY MONDAY MORNING...AND HAVE ALSO EXTENDED FERGUS
COUNTY OUT OVERNIGHT ON SUNDAY AS WELL. MPJ
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.AVIATION...
UPDATED 0040Z.
A DEEP UPPER LEVEL TROUGH OF LOW PRESSURE WILL REMAIN OVER WESTERN
AND CENTRAL MONTANA AT LEAST THROUGH SATURDAY WITH THE UPPER LOW
PRESSURE CENTER SOUTH OF THE AREA OVER THE GREAT BASIN AND CENTRAL
ROCKIES. THE RESULTING MOIST EASTERLY UPSLOPE FLOW OVER THE AREA
WILL CONTINUE THE WIDESPREAD CLOUDINESS AND OCCASIONAL SNOW.
CONDITIONS WILL MOSTLY BE LOW VFR/HIGH MVFR ACROSS SOUTHWEST (KBZN
AND KHLN TERMINALS) AND CENTRAL (KLWT AND KGTF) MONTANA. SOME
HEAVIER SHOWERS ACROSS THESE AREAS MAY CAUSE OCCASIONAL IFR
CONDITIONS...MAINLY OVERNIGHT. CLOUDS AND SNOW WILL BE A BIT MORE
SCARCE ACROSS NORTH CENTRAL MONTANA (KCTB AND KHVR)...FOR MOSTLY VFR
CONDITIONS THERE. HOWEVER...A FEW SHOWERS MAY CAUSE BRIEF MVFR
CONDITIONS AT KHVR THROUGH 06Z...AND MORE WIDESPREAD MVFR CEILINGS
WILL DEVELOP DURING THE OVERNIGHT HOURS AT KCTB. WINDS WILL MOSTLY
BE BREEZY AND NORTHEASTERLY...WITH WINDS INCREASING DURING THE DAY
ON SATURDAY. COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 34 22 35 / 30 40 50 30
CTB 21 35 19 40 / 20 20 20 10
HLN 29 36 27 37 / 60 60 50 50
BZN 26 37 25 34 / 80 80 80 70
WEY 19 30 18 27 / 90 80 90 60
DLN 21 30 18 31 / 90 70 80 50
HVR 24 41 21 38 / 20 20 20 30
LWT 23 31 19 29 / 70 80 80 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING CONTINUES UNTIL 6 PM MDT SUNDAY FOR
MTZ008-012-014-015-050-052>055.
WINTER STORM WARNING CONTINUES UNTIL 6 AM MDT MONDAY FOR MTZ051.
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 AM MDT MONDAY FOR
MTZ047.
&&
$$
SHORT TERM...MPJ
LONG TERM...ZELZER/SAUCIER
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KGGW 102151
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
351 PM MDT FRI OCT 10 2008
...A MAJOR WINTER STORM IS EXPECTED TO IMPACT THE REGION
SATURDAY NIGHT THROUGH MONDAY MORNING...
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
CURRENT GOES WATER VAPOR IMAGERY REVEALS A DEEPENING UPPER LEVEL
TROUGH OVER THE GREAT BASIN. AT THE SURFACE...A LOW PRESSURE
SYSTEM IS DEVELOPING OVER COLORADO AND A CANADIAN HIGH PRESSURE
SYSTEM IS SITUATED OVER ALBERTA. AN UPPER JET STREAK IS PASSING ABOVE
EASTERN MONTANA THIS AFTERNOON...WHICH HAS RESULTED IN LIGHT RAIN
AND HIGH ELEVATION SNOW SOUTH OF THE MISSOURI RIVER. THIS PATTERN
WILL PERSIST THROUGH SATURDAY MORNING AS THE UPPER JET STREAK
STRENGTHENS IN THE ENTRANCE REGION.
BY SATURDAY AFTERNOON A JET STREAK ROUNDS THE BASE OF THE UPPER
TROUGH AND COUPLES WITH AFOREMENTIONED UPSTREAM WAVE. THE SURFACE
LOW ORGANIZES AND MOVES INTO CENTRAL SOUTH DAKOTA BY SUNDAY
MORNING WHILE THE SURFACE HIGH RETREATS TO THE EAST.
MEANWHILE...SUBTROPICAL MOISTURE WILL BE DRAWN NORTHWARD FROM THE
REMNANTS OF HURRICANE NORBERT. THIS WILL PRODUCE HEAVY SNOW ACROSS
NORTHEAST MONTANA SATURDAY NIGHT AND SUNDAY...WHICH HAS THE
POTENTIAL TO PERSIST LONGER AS MODELS DEVELOP A ROBUST TROWAL
SIGNATURE OVER MUCH OF THE AREA. THE DRY SLOT IS FORECAST TO MOVE
FROM SOUTHEAST MONTANA INTO WESTERN NORTH DAKOTA...BUT A SLIGHT
SHIFT IN TRACK COULD LEAD TO A QUICKER END OF THE SNOW IN THE
EASTERN ZONES.
6 TO 12 INCHES WITH LOCALLY HIGHER AMOUNTS IS A REASONABLE
ACCUMULATION FORECAST AT THIS POINT. MODEL QPF AMOUNTS SUGGEST
HIGHER. HOWEVER...SNOW WILL HAVE SOME TROUBLE ACCUMULATING
INITIALLY AS THE SURFACE AND SUBSURFACE REMAIN WARM GIVEN THE TIME
OF YEAR. A MODERATELY STRONG NORTH WIND WILL DEVELOP...WHICH HAS
THE POTENTIAL TO PRODUCE BLOWING AND DRIFTING.
TEMPERATURES WILL FALL INTO THE LOW 30S AT THE ONSET OF THE STORM
SYSTEM AND REMAIN IN THAT VICINITY THROUGH THE PERIOD. AJZ
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
ALL CHANGES WERE CONTAINED TO THE EARLY PART OF THE PERIOD TO HELP
HANDLE THE ONGOING MAJOR WINTER STORM. BIGGEST CHANGE INVOLVED THE NEW
RUNS OF THE DGEX...GFS...AND NAM WHICH ARE ALL CONSISTENT WITH A
SLOWER EXIT OF THE UPPER LOW. THE GFS ENSEMBLES ALSO HEAVILY FAVOR
A SLOWER SOLUTION. THE OUTLIER CONTINUES TO BE THE ECMWF. IT TAKES
THE LOW OUT OF EASTERN MONTANA ON SUNDAY AFTERNOON AND MOVES IT TO
HUDSON BAY CANADA BY MONDAY AFTERNOON...SOME 800 MILES IN 24
HOURS. GIVEN THE BETTER CONSENSUS IN A SLOWER SOLUTION RAMPED UP
POPS TO COVER THE LINGERING EFFECTS OF THE LOW ACROSS NORTHEAST
MONTANA. DUE TO THIS CHANGE THE WINTER STORM WARNING WILL BE
PUSHED INTO SUNDAY NIGHT. GILCHRIST
PREVIOUS LONG TERM DISCUSSION...STORM VORTEX WILL BEGIN LIFTING
OUT OF NORTHEAST MONTANA SUNDAY NIGHT. WRAP-AROUND ENERGY FROM THE
NORTHERLY FLOW ON THE WEST SIDE OF THE LOW WILL FOCUS QPF OVER THE
NORTHERN ZONES FOR ADDITIONAL TAPERING OFF SNOWFALL. RISING
HEIGHTS FROM THE WEST MONDAY WILL CUT OFF ANY REMAINING
PRECIPITATION. THE POSITIVE LEANING RIDGE WILL BE QUICKLY
FLATTENED BY A QUICK-MOVING SHORTWAVE ACROSS ALBERTA AND
SASKATCHEWAN MONDAY NIGHT. THE 00Z GFS SHORTWAVE IS MORE SHALLOW
THAN THE 12/00Z ECMWF SHORTWAVE. TUESDAY AND WEDNESDAY THE MODELS
SEND ADDITIONAL WEAK SHORTWAVES ACROSS CANADA...NOT NECESSARILY IN
AGREEMENT WITH EACH OTHER. BUT AROUND WEDNESDAY NIGHT OR THURSDAY
AN UPPER RIDGE SLOWLY BUILDS UP OVER THE WEST...MAINTAINING UPPER
FLOW FROM THE NORTHWEST LOCALLY. AFTER THE PASSAGE OF THE SUNDAY
NIGHT STORM THE CONDITIONS WILL GENERALLY DRY AND COOL...WITH THE
POSSIBILITY OF WARMING TO NORMAL BY THE END OF THE PERIOD. SCT
&&
.AVIATION...
AN EARLY SEASON WINTER STORM CONTINUES TO IMPACT NORTHEAST
MONTANA. THE FOCUS OF THE SYSTEM WILL BE ALONG A STALLED FRONTAL
BOUNDARY THAT EXTENDS FROM SIDNEY SOUTHEAST TOWARDS LEWISTOWN.
AREAS SOUTH AND EAST OF THIS LINE WILL SEE PREDOMINATELY MVFR
CONDITIONS WITH LIGHT RAIN AND SNOWFALL...INCLUDING THE KSDY AND
KGDV TERMINALS. LATE TONIGHT THIS AREA WILL SEE CEILINGS COME
CRASHING DOWN TO IFR AS LOWER LEVEL MOISTURE CONTINUES TO MOVE IN.
AREAS NORTH AND WEST OF THE BOUNDARY WILL SEE VFR CONDITIONS OVER
THE NEXT 24 HOURS AS MID AND HIGH LEVEL CLOUDS RULE...THIS
INCLUDES THE KGGW AND KOLF TERMINALS.
ALL TERMINALS WILL SEE NORTHEAST WINDS AROUND 15 KTS DECREASING
TO 8KTS AROUND SUNSET. WINDS WILL AGAIN PICK UP AROUND 12Z.
A MAJOR WINTER STORM SYSTEM IS SET TO IMPACT NORTHEAST MONTANA
SUNDAY NIGHT INTO MONDAY NIGHT. EXPECT WIDESPREAD IFR CEILINGS AND
VISIBILITIES DURING THIS TIME...ALONG WITH GUSTY NORTH TO EAST
WINDS AT 15 TO 25 KTS. GILCHRIST
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 AM MDT MONDAY FOR
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-NORTHERN PHILLIPS-SOUTHWEST
PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT.
WINTER STORM WARNING FROM 12 PM SATURDAY TO 6 AM MDT MONDAY FOR
PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-WIBAUX.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 102146
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
346 PM MDT FRI OCT 10 2008
...MAJOR WINTER STORM WILL CONTINUE TO IMPACT THE AREA THROUGH
SUNDAY NIGHT...
.SHORT TERM...VALID FOR SAT AND SUN...
MODELS WERE SIMILAR IN HANDLING MAJOR WINTER STORM SYSTEM THROUGH
SUN...THEN BEGAN TO DIVERGE WITH SPEED OF SYSTEM EXITING THE AREA
SUN NIGHT. CURRENT WINTER STORM WARNINGS WERE IN GOOD SHAPE.
UPPER DIFLUENCE WAS EVIDENT ON SATELLITE AND RADAR IMAGERY THIS
AFTERNOON AS UPPER LOW DIGS SOUTH THRU THE WESTERN U.S..
SHORTWAVE OVER WY...PER RADAR IMAGERY...WILL PUSH N INTO THE AREA
THIS EVENING. STRONG UPPER JET WILL DIG S ON BACK SIDE OF UPPER
LOW CAUSING THE LOW TO CONTINUE TO DEEPEN AND MOVE TO S NV BY 12Z
SAT. PRECIPITABLE WATERS S AND SE OF AREA WERE 120-130 PERCENT OF
NORMAL BACK AT 12Z. ISENTROPIC LIFT AND LOW TO MID LEVEL E FLOW
WILL CONTINUE OVERNIGHT AND DENDRITIC GROWTH LAYER WILL REMAIN
ABOVE THE BEST LIFT. LIGHT SNOW WILL CONTINUE OVERNIGHT AND EXPECT
RAIN/SNOW MIX NE TO CHANGE TO ALL SNOW AFTER SUNSET. CONTINUED
CATEGORICAL POPS ACROSS THE REGION TONIGHT. UPSLOPE AREAS HAD
RECEIVED 8 TO 14 INCHES SO FAR SINCE SNOW BEGAN LATE THU NIGHT.
BUMPED UP AMOUNTS IN THOSE AREAS OVERNIGHT. MADE SMALL ADJUSTMENTS
TO MIN TEMPERATURES BASED ON BIAS CORRECTED MET GUIDANCE.
THE UPPER LOW WAS FORECAST TO MOVE TO NEAR KSLC BY 00Z SUN
CONSISTENT WITH PREVIOUS MODEL RUNS. UPPER JET STRENGTHENS ON E SIDE
OF THE LOW ON SAT AND CONTINUES TO STRENGTHEN SAT NIGHT. DIFLUENCE
WILL INCREASE OVER THE AREA DURING SAT AND CONTINUE SAT NIGHT. WEAK
WAVES WILL PUSH N THROUGH THE REGION SAT. ISENTROPIC LIFT AND THE
EASTERLY FLOW WILL CONTINUE OVER THE AREA. WENT WITH CATEGORICAL
POPS IN ALL AREAS AND INCREASED SNOW AMOUNTS IN THE FOOTHILLS.
EXPECT EASTERLY WINDS TO BE QUITE STRONG IN KLVM AREA ON SAT.
UPPER LOW THEN WOBBLES SLIGHTLY NE SAT NIGHT AND SENDS STRONG
SHORTWAVE ENERGY INTO THE EASTERN PART OF THE AREA. COUPLED JET
STRUCTURE WILL CREATE STRONG DIVERGENCE OVER THE AREA. EASTERN
ZONES WILL STILL BE WARMER AT 700 MB THEN LOCATIONS CENTRAL AND W.
HOWEVER...KBHK TIME-HEIGHT CROSS SECTION HAD DEEP OMEGA
INTERSECTING FAVORABLE DENDRITIC GROWTH ZONE. THUS WILL FORECAST
NEAR A FOOT OF SNOW OVER FAR E AND SE ZONES SAT NIGHT. MOST AREAS
WILL HAVE HIGHER SNOW AMOUNTS THIS PERIOD THAN PREVIOUS PERIODS
DUE TO THE INCREASED DYNAMICS. LOWERED MIN TEMPERATURES TOWARD
BIAS CORRECTED MET AS 850 MB TEMPS WILL BE NEAR -4 DEG C.
WITH ENERGY MOVING INTO E MT...UPPER LOW CENTER REDEVELOPS OVER THIS
AREA ON SUN AND PULLS COLDER AIR INTO THE AREA. DENDRITIC LAYER OVER
CENTRAL AND EASTERN AREAS LOWERS ON SUN AND INTERSECTS DECENT LIFT
PER MODEL TIME-HEIGHT CROSS SECTIONS. KEPT HIGH POPS ACROSS THE AREA
AND NUDGED SNOW AMOUNTS UP IN A FEW AREAS. LATER SHIFTS MAY NEED TO
RAISE AMOUNTS EVEN MORE IF STRONG LIFT CONTINUES TO PERSIST INTO SUN
ON LATER MODEL RUNS.
LATEST MODELS THEN DIVERGED FOR SUN NIGHT. ECMWF AND WRF MOVED THE
LOW NE OUT OF THE AREA. GFS WAS MUCH SLOWER AND KEPT THE LOW OVER E
MT. WILL FOLLOW A COMPROMISE BETWEEN MODEL SOLUTIONS AND RAISE POPS
OVER E PORTION OF THE FORECAST AREA. DROPPED HIGHS TOWARD BIAS
CORRECTED MET WITH -4 TO -6 DEG C AT 850 MB. ARTHUR
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
UPPER LEVEL LOW PRESSURE EXITING THE REGION ON MONDAY BUT A CHANCE
FOR WRAP AROUND PRECIPITATION INTO THE AREA STILL EXISTS DURING
THE DAY...ESPECIALLY THE MORNING HOURS. NAM AND ECMWF ARE IN
AGREEMENT WITH TRYING TO PULL THE LOW FURTHER AWAY FROM THE AREA
WITH CURRENT TRENDS SHOWING THE WRF PULLING THE LOW FURTHER AWAY
THAN PREVIOUS RUNS. STILL THINK GIVEN IT STILL COULD BE WINTRY ON
MONDAY IS WORTH INTRODUCING IN THE FORECAST. STRONG NORTHWESTERLY
FLOW ALOFT REPLACES THE UPPER LOW ON TUESDAY AND ASSUMING THAT
SNOW COVER SHOULD BE SOLID ENOUGH TO HAVE A DRAMATIC IMPACT ON
TEMPERATURES DESPITE SUNSHINE. WEDNESDAY AND THURSDAY SHOULD STAY
COOL AS WEAK RIDGING BUILDS WEST OF THE AREA AND KEEPS SURFACE
HIGH PRESSURE AND WEAK MIXING IN PLACE. TEMPERATURES WILL HAVE TO
WATCHED CLOSELY AND ADJUSTED DOWNWARD IF SNOWFALL AMOUNTS END UP
AS WIDESPREAD AS EXPECTED. PROGRESSION OF RIDGE INTO THE AREA ON
FRIDAY GIVES A BETTER CHANCE FOR WARMING AND MORE FLOW OVER THE
CANADIAN ROCKIES MAY FAVOR A BETTER DOWNSLOPE PATTERN DEVELOPING.
HOWEVER...GREAT BASIN SURFACE HIGH PRESSURES MAY NOT BE THAT
SIGNIFICANT SO GAP FLOW WINDS MAY NOT BE AS STRONG AS NORMAL.
BORSUM
&&
.AVIATION...
A LARGE WINTER STORM WILL KEEP WIDESPREAD IFR CONDITIONS ACROSS
THE REGION WITH AREAS OF LIFR CONDITIONS THROUGH SATURDAY NIGHT.
BORSUM
&&
.PRELIMINARY POINT TEMP/POPS...
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 028/033 026/033 023/035 027/050 032/053 033/054 035/060
++/S +8/S 47/S 10/B 11/B 11/B 11/B
LVM 021/032 017/034 022/041 026/050 032/053 033/054 035/059
++/S +8/S 35/S 10/B 11/B 21/B 11/B
HDN 027/034 027/037 022/038 026/051 031/054 032/055 034/062
++/S +9/S 56/S 10/B 11/B 11/B 11/B
MLS 027/037 025/036 024/038 028/052 032/055 033/056 035/061
++/O +9/S 55/S 21/B 11/B 21/U 11/U
4BQ 026/035 026/035 023/038 027/052 030/055 031/056 033/061
++/S +9/S 53/S 10/U 11/U 21/B 11/U
BHK 024/035 023/035 022/040 023/050 029/053 031/054 034/059
++/O +9/S 54/S 11/B 11/B 21/B 11/B
SHR 023/034 023/034 022/037 026/050 029/053 031/054 033/060
++/S +9/S 35/S 10/U 11/U 12/W 21/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 28>42-56>58-63>68.
WY...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 102059
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
259 PM MDT FRI OCT 10 2008
.DISCUSSION...
TONIGHT THROUGH SUNDAY...EARLY SEASON WINTER STORM WILL CONTINUE
TO IMPACT SOUTHWEST MONTANA AND SOUTHERN PORTIONS OF CENTRAL
MONTANA. HOWEVER...MOST OF NORTH CENTRAL MONTANA REMAINS BENEATH
PARTLY CLOUDY TO MOSTLY CLOUDY SKIES WITH ONLY A SLIGHT CHANCE TO
CHANCE OF SNOW EXPECTED DURING THE SHORT TERM PERIOD. THE DEEP
UPPER LEVEL LOW WILL CONTINUE TO SPIN OVER THE GREAT BASIN THROUGH
SATURDAY THEN WILL FINALLY BEGIN TO LIFT OUT TO THE NORTHEAST
SATURDAY NIGHT AND SUNDAY. AS THE LOW LIFTS OUT...PRECIPITATION
WILL BEGIN TO TAPER OFF IN SOUTHWEST MONTANA. AT THE SAME TIME A
COMBINATION OF STRONG UPPER LEVEL FORCING AND LOW LEVEL
FRONTOGENESIS WILL CAUSE A SIGNIFICANT BAND OF PRECIPITATION
ACROSS EASTERN PORTIONS OF MY CWA. HAVE OPTED TO ADD BLAINE COUNTY
TO THE WINTER STORM WARNING FOR THE PERIOD OF SATURDAY NIGHT
THROUGH EARLY MONDAY MORNING...AND HAVE ALSO EXTENDED FERGUS
COUNTY OUT OVERNIGHT ON SUNDAY AS WELL. MPJ
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.AVIATION...
UPDATED 1750Z.
A DEEP UPPER LEVEL LOW PRESSURE TROF WILL REMAIN OVER THE AREA
THROUGH SATURDAY KEEPING THE AIRMASS COOL AND MOIST. PERIODS OF SNOW
AND LOW CIGS WILL CAUSE AREAS OF MVFR CONDITIONS ACROSS SOUTHWEST
MONTANA AND PORTIONS OF NORTH CENTRAL MONTANA. VFR CONDITIONS WILL
PREVAIL OVER MUCH OF NORTH CENTRAL MONTANA AND THE CANADIAN BORDER
WITH PERIODS OF MVFR CONDITIONS WITH SNOW SHOWERS AND FOG. SURFACE
FLOW WILL GENERALLY REMAIN NORTHEAST AND BRISK.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 34 22 35 / 30 40 50 30
CTB 21 35 19 40 / 20 20 20 10
HLN 29 36 27 37 / 60 60 50 50
BZN 26 37 25 34 / 80 80 80 70
WEY 19 30 18 27 / 90 80 90 60
DLN 21 30 18 31 / 90 70 80 50
HVR 24 41 21 38 / 20 20 20 30
LWT 23 31 19 29 / 70 80 80 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING CONTINUES UNTIL 6 PM MDT SUNDAY FOR
MTZ008-012-014- 015-050-052>055.
WINTER STORM WARNING CONTINUES UNTIL 6 AM MDT MONDAY FOR MTZ051.
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 AM MDT MONDAY FOR
MTZ047.
&&
$$
SHORT TERM...MPJ
LONG TERM...ZELZER/SAUCIER
AVIATION...LOSS
WEATHER.GOV/GREATFALLS
000
FXUS65 KMSO 102035
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
235 PM MDT FRI OCT 10 2008
.DISCUSSION...COOL AND MOIST UPPER TROUGH CONTINUES TO ROTATE AND
ELONGATE OVER THE NORTHWEST PORTION OF THE U.S. THE RESULT HAS
BEEN PERSISTENT LARGE SCALE LIFT OVER CENTRAL IDAHO AND SOUTHWEST
MONTANA. THE BEST COMBINATION OF LIFT AND AVAILABLE MOISTURE WAS
LAST NIGHT THROUGH MID MORNING. ACCUMULATING SNOW HAS DIMINISHED
ACROSS MOST AREAS SINCE THEN...BUT WITH THE ATMOSPHERIC ASCENT
EXPECTED THROUGH AT LEAST ANOTHER 24 HOURS...WILL KEEP A WINTER
HIGHLIGHT IN PLACE. HAVE DECIDED TO SCALE THE WARNINGS DOWN TO
WINTER WEATHER ADVISORIES TO COVER THE PERSISTENT LIGHT
ACCUMULATIONS. THESE ACCUMULATIONS COULD CONTINUE THROUGH SUNDAY
AFTERNOON WITH THE SLOW MOVING NATURE OF THE UPPER TROUGH.
HOWEVER...FOR NOW WILL ONLY MAINTAIN THE ADVISORY THROUGH SATURDAY
AFTERNOON AND SEE IF THE TROUGH CAN TRULY SUSTAIN THE LIFT.
THE NORTH TO NORTHEAST GRADIENT WILL ALSO CONTINUE TONIGHT AND
SATURDAY MAINTAINING BRISK SURFACE WINDS.
LATE SUNDAY NIGHT AND MONDAY THE TROUGH WILL MOVE EAST INTO THE
NORTHERN PLAINS ALLOWING A BRIEF DRY RIDGE TO DEVELOP. THIS WILL
HELP MODERATE TEMPERATURES. THIS RIDGING WILL NOT LAST LONG AS A
WESTERLY UPPER LEVEL FLOW PUSHES OVER THE NORTHERN STATES MIDWEEK.
THIS DOES NOT LOOK LIKE A VERY WET PATTERN BUT COULD PRODUCE SOME
SHOWERS OVER THE MOUNTAINS. BROAD RIDGING WILL AGAIN DRY THE
REGION OUT LATE IN THE COMING WEEK.
&&
.AVIATION...WIDESPREAD MOUNTAIN OBSCURATIONS IN CLOUDS AND SNOW
WILL PERSIST OVER NORTH CENTRAL IDAHO AND SOUTHWEST MONTANA
TONIGHT...AND LIKELY THROUGH THE WEEKEND. VALLEYS WILL
OCCASIONALLY SEE SNOW AND BLOWING SNOW RESULTING IN REDUCED
VISIBILITIES IN THESE SAME AREAS...BUT PERSISTENT IFR CONDITIONS
ARE NOT EXPECTED. NORTH TO NORTHEAST SURFACE WINDS WILL BE
WIDESPREAD THROUGH SATURDAY EVENING WITH TYPICAL SUSTAINED
VALUES PEAKING AROUND 20 KTS AND SOME GUSTS TO 30 KTS.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY UNTIL 6 PM MDT SATURDAY FOR
BUTTE/BLACKFOOT REGION.
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER WEATHER ADVISORY UNTIL 6 PM MDT SATURDAY FOR EASTERN
LEMHI COUNTY.
&&
$$
WHITMORE/ALLEGRETTO/DEROSA
000
FXUS65 KTFX 101754
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1150 AM MDT FRI OCT 10 2008
.UPDATE...EARLY SEASON WINTER STORM CONTINUES TO BUILD STRENGTH
ACROSS THE REGION THIS MORNING. LOOKS LIKE YESTERDAYS MODELS
TOOK THE PRECIPITATION TOO FAR TO THE NORTHWEST IN CENTRAL MONTANA
AS MY SOUTHERN AND SOUTHEAST ZONES ARE CURRENTLY TAKING THE BRUNT
OF THE STORM. HAVE HAD REPORTS OF 8 INCHES ACCUMULATION NEAR GRANT
IN BEAVERHEAD COUNTY...AND 5 INCHES AT HALF MOON PASS ON THE EAST
SIDE OF THE BIG SNOWY MOUNTAINS IN FERGUS COUNTY. MAIN CHANGE IN
THE UPDATE WAS TO LOWER POPS OVER MY NORTHERN PLAINS...INCLUDING
AT GREAT FALLS WHERE POPS FOR TODAY HAVE BEEN DROPPED DOWN TO A
CHANCE ONLY. THE WARNING WILL CONTINUE FOR ALL OF SOUTHWEST
MONTANA AND THE SOUTHERN PORTION OF CENTRAL MONTANA. ONLY OTHER
CHANGE TO THE FORECAST WERE SOME MINOR TWEAKS TO TEMPERATURES AND
TO SLIGHTLY ADJUST SNOW LEVELS AND SUBSEQUENT PRECIPITATION TYPE.
MPJ
&&
.AVIATION...
UPDATED 1750Z.
A DEEP UPPER LEVEL LOW PRESSURE TROF WILL REMAIN OVER THE AREA
THROUGH SATURDAY KEEPING THE AIRMASS COOL AND MOIST. PERIODS OF SNOW
AND LOW CIGS WILL CAUSE AREAS OF MVFR CONDITIONS ACROSS SOUTHWEST
MONTANA AND PORTIONS OF NORTH CENTRAL MONTANA. VFR CONDITIONS WILL
PREVAIL OVER MUCH OF NORTH CENTRAL MONTANA AND THE CANADIAN BORDER
WITH PERIODS OF MVFR CONDITIONS WITH SNOW SHOWERS AND FOG. SURFACE
FLOW WILL GENERALLY REMAIN NORTHEAST AND BRISK.
&&
.PREV DISCUSSION...
/ISSUED 548 AM MDT FRI OCT 10 2008/
TODAY THROUGH SUNDAY...AN UPPER LEVEL LOW OVER SOUTHERN IDAHO...WILL
CONTINUE TO DEEPEN THROUGH THE DAY...WITH MOST DYNAMICS WELL SOUTH
OF MONTANA. HOWEVER...ABUNDANT MOISTURE WILL MOVE NORTHWARD INTO
THE REGION THROUGH THE WEEKEND. A GOOD UPSLOPE SURFACE PATTERN WILL
CONTINUES EAST OF THE DIVIDE THROUGH SUNDAY...BETWEEN A DEEPENING
SURFACE LOW OVER UTAH AND A CANADIAN SURFACE HIGH OVER CENTRAL
ALBERTA. THUS...A WINTER STORM WARNING WILL REMAIN TODAY THROUGH
SUNDAY AFTERNOON FOR MOST OF SOUTHWEST MONTANA AND THE SOUTHERN HALF
OF NORTH CENTRAL MONTANA. SNOW IS EXPECTED TO BE HEAVY AT TIMES WITH
ACCUMULATIONS OF 15 TO 30 INCHES OVER THE MOUNTAINS AND
3 TO 6 INCHES ACROSS THE PLAINS AND VALLEYS BY SUNDAY EVENING.
THERE WILL BE SOME MELTING OF SNOW...DUE TO WARM GROUND...AT LOWER
ELEVATIONS. THE BEST CHANCE FOR HEAVY SNOW WILL BE SATURDAY AFTERNOON
AND SATURDAY NIGHT...AS THE UPPER LOW MOVES NORTHEAST INTO SOUTHEAST
MONTANA BY SUNDAY EVENING. IT WILL BE UNSEASONABLY COLD THROUGH
SUNDAY...WITH TEMPERATURES RUNNING SOME 20 TO 30 DEGREES BELOW
SEASONAL AVERAGE. HIGHWAYS WILL BECOME ICY AT LOWER
ELEVATIONS...ESPECIALLY DURING THE NIGHT AND MORNING HOURS ALONG
WITH SOME BLOWING SNOW THROUGH THE PASSES AND CANYONS. CONDITIONS
WILL IMPROVE FROM THE NORTHWEST AS AN UPPER LEVEL RIDGE OF HIGH
PRESSURE OVER THE WEST COAST...BUILDS INTO CENTRAL ALBERTA.
WILLIAMSON DC
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 37 23 34 21 / 30 60 60 40
CTB 39 21 34 17 / 20 30 30 10
HLN 40 25 34 25 / 60 60 50 50
BZN 40 26 36 25 / 100 80 80 80
WEY 33 19 30 16 / 90 90 80 80
DLN 34 20 30 17 / 80 60 50 80
HVR 45 25 39 18 / 20 30 30 10
LWT 36 22 30 17 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM MDT SUNDAY FOR MTZ008-012-014-
015-050>055.
&&
$$
SHORT TERM...MPJ/WILLIAMSON DC
LONG TERM...ZELZER/SAUCIER
AVIATION...LOSS
WEATHER.GOV/GREATFALLS
000
FXUS65 KGGW 101611 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
1011 AM MDT FRI OCT 10 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SUNDAY...
A DEEP TROUGH IS SITUATED OVER THE INTERMOUNTAIN WEST THIS MORNING
WITH PRESSURE FALLS TO THE LEE OF THE ROCKIES OVER THE CENTRAL
PLAINS. THESE PRESSURE FALLS ARE COMBINING WITH HIGH PRESSURE
BUILDING SOUTH IN ALBERTA TO PRODUCE A LARGE UPSLOPE OREINTED PRESSURE
GRADIENT FROM WYOMING INTO MONTANA. AN UPPER JET IS PUSHING OVER
EASTERN MONTANA AND DRINVING AN AREA OF PRECIPITATION SOUTH OF
THE MISSOURI RIVER. THIS SHOULD PERSIST THROUGH THE REMAINDER OF
THE DAY AS THERE WILL BE A SHARP GRADIENT IN PRECIPITATION WITH
DRIER AIR PUSHING SOUTH FROM THE CANADIAN PRAIRIES. GENERALLY
PRECIPITATION TYPE WILL BE SNOW ABOVE 3000FT...RAIN AND SNOW MIX
FROM 2500-3000FT...AND RAIN BELOW. WILL CONTINE WITH THE WINTER
STORM WARNING AS IT IS THE FIRST WINTER STORM OF THE SEASON.
OVERALL FORECAST IS IN GOOD SHAPE WITH ONLY A FEW TWEAKS TO POPS
AND TEMPERATURES. AJZ
PREVIOUS SHORT TERM DISCUSSION...
UPPER TROUGH DIGGING INTO THE GREAT BASIN WILL CONTINUE TO BRING
SOUTHWEST FLOW ALOFT TO MONTANA TODAY AND TONIGHT. MOISTURE
OVERRUNNING A FRONTAL BOUNDARY WELL SOUTH OF MONTANA HAS BROUGHT A
MIX OF RAIN AND SNOW TO SOUTHEAST MONTANA OVERNIGHT. THE
PRECIPITATION IS GENERALLY SOUTH OF WINNETT... JORDAN AND GLENDIVE
AT 10Z. THE PRECIPITATION WILL MAKE MINIMAL PROGRESS FURTHER NORTH
TODAY AS LOW LEVEL DRY AIR FROM THE NORTH KEEPS THE RAIN AND SNOW
SOUTH OF THE MISSOURI RIVER. WITH TEMPERATURES NEAR FREEZING AT
HIGHER ELEVATION SITES LIKE BIG SHEEP MOUNTAIN RAWS...WILL KEEP
WINTER STORM WARNING IN PLACE AS WET HEAVY SNOW IS STILL LIKELY IN
HIGHER ELEVATION AREAS.
THE OVERRUNNING MOISTURE WILL MOVE TO THE EAST THIS EVENING
ALLOWING A BREAK IN THE PRECIPITATION TONIGHT. MEANWHILE...A
CLOSED UPPER LOW WILL FORM AT THE BASE ON THE UPPER TROUGH OVER
NEVADA TODAY AND DEEPEN AS IT MOVES SLOWLY NORTHEAST TONIGHT AND
SATURDAY.
THE NEXT SURGE OF MOISTURE WILL MOVE NORTH SATURDAY AND WITH
TEMPERATURES COLD ENOUGH ALOFT...WIDESPREAD SNOW WILL DEVELOP FROM
SOUTH TO NORTH ACROSS NORTHEAST MONTANA SATURDAY AFTERNOON AND EVENING.
THE UPPER LOW WILL LIFT NORTHEAST ACROSS EASTERN MONTANA ON
SUNDAY. WITH GULF OF MEXICO MOISTURE FEEDING THIS SYSTEM...HEAVY
SNOW IS LIKELY ACROSS MOST OF NORTHEAST MONTANA SATURDAY NIGHT AND
SUNDAY. WILL MAINTAIN GOING WINTER STORM WATCH FOR NOW. NORTH
WINDS 15 TO 30 MPH WILL BLOW AND DRIFT ANY OF THE SNOW THAT FALLS.
FORECAST MODELS ARE HINTING AT A FOOT OR MORE OF SNOW FOR PARTS OF
THE FORECAST AREA FROM THIS STORM. FORRESTER
PREVIOUS SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH
SATURDAY...A BUSY FEW DAYS...WEATHER WISE...IN STORE FOR NORTHEAST
MONTANA. AN UPPER TROUGH DIGGING INTO THE GREAT BASIN WILL EJECT
WARMER MORE MOIST AIR OVER A POLAR AIRMASS IN PLACE OVER EASTERN
MONTANA. THIS OVERRUNNING WILL DRIVE A MIX OF RAIN AND SNOW ACROSS
THE SOUTHERN ZONES...MAINLY SOUTH OF HIGHWAY 200. HAVE UPGRADED
THE EXISTING WATCH FOR THE SOUTHERN ZONES TO A WINTER STORM
WARNING. NORTHERLY WINDS OF 15 TO 25 MPH WILL ACCOMPANY THE
STORM...HOWEVER GIVEN THE HEAVY WET NATURE TO THE SNOWFALL DO NOT
EXPECT MUCH IN THE WAY OF BLOWING AND DRIFTING. THESE WINDS MAY
ALSO REQUIRE A LAKE WIND ADVISORY FOR FORT PECK LAKE FRIDAY
AFTERNOON. BY FRIDAY EVENING THE LIFT GENERATED BY THE OVERRUNNING
WILL TAPER OFF...SUBSEQUENTLY TAPERING OFF THE RAIN AND SNOW. THIS
LULL WILL LAST INTO SATURDAY MORNING...BEFORE A SECOND MORE
POTENT/WET SYSTEM MOVES IN FROM THE SOUTH. COORDINATED A WATCH
WITH THE EXTENDED FORECASTER THAT STARTS SATURDAY AFTERNOON FOR
AREAS SOUTH OF THE MISSOURI RIVER. SIGNIFICANT SNOW ACCUMULATION
CAN BE EXPECTED ACROSS THE WHOLE OF NORTHEAST MONTANA WITH THIS
SECOND STORM SYSTEM. GILCHRIST
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
STORM VORTEX WILL BEGIN LIFTING OUT OF NORTHEAST MONTANA SUNDAY
NIGHT. WRAP-AROUND ENERGY FROM THE NORTHERLY FLOW ON THE WEST
SIDE OF THE LOW WILL FOCUS QPF OVER THE NORTHERN ZONES FOR
ADDITIONAL TAPERING OFF SNOWFALL. RISING HEIGHTS FROM THE WEST
MONDAY WILL CUT OFF ANY REMAINING PRECIPITATION. THE POSITIVE
LEANING RIDGE WILL BE QUICKLY FLATTENED BY A QUICK-MOVING
SHORTWAVE ACROSS ALBERTA AND SASKATCHEWAN MONDAY NIGHT. THE 00Z
GFS SHORTWAVE IS MORE SHALLOW THAN THE 12/00Z ECMWF SHORTWAVE.
TUESDAY AND WEDNESDAY THE MODELS SEND ADDITIONAL WEAK SHORTWAVES
ACROSS CANADA...NOT NECESSARILY IN AGREEMENT WITH EACH OTHER. BUT
AROUND WEDNESDAY NIGHT OR THURSDAY AN UPPER RIDGE SLOWLY BUILDS UP
OVER THE WEST...MAINTAINING UPPER FLOW FROM THE NORTHWEST LOCALLY.
AFTER THE PASSAGE OF THE SUNDAY NIGHT STORM THE CONDITIONS WILL
GENERALLY DRY AND COOL...WITH THE POSSIBILITY OF WARMING TO NORMAL
BY THE END OF THE PERIOD. SCT
&&
.AVIATION...
A STORM SYSTEM EJECTING RAIN AND SNOW NORTHEAST ACROSS EASTERN
MONTANA AND THE WESTERN DAKOTAS WILL CONTINUE TO LIFT NORTH TODAY
BRINGING WIDESPREAD CLOUD COVER. CEILINGS WILL VARY FROM VFR NORTH
OF THE MISSOURI RIVER TO MVFR SOUTH. RAIN AND SNOW WILL ALSO
FALL...IMPACTING AREAS SOUTH AND EAST OF A WINNETT TO SIDNEY LINE.
BRIEF PERIODS OF IFR CONDITIONS ARE POSSIBLE IN REGIONS OF HEAVIER
PRECIPITATION. NORTHEAST WINDS OF 15-25KTS CAN BE EXPECTED THIS
AFTERNOON THROUGH SUNSET...BEFORE DIMINISHING TO LESS THEN 12 KTS.
SCT/GILCHRIST
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND
SOUTHERN VALLEY-DANIELS-SHERIDAN-WESTERN ROOSEVELT-NORTHERN
PHILLIPS-SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT.
WINTER STORM WARNING UNTIL 6 PM MDT THIS AFTERNOON FOR PETROLEUM-
GARFIELD-DAWSON-PRAIRIE-WIBAUX.
WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
AFTERNOON FOR PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-
WIBAUX.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 101559
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
959 AM MDT FRI OCT 10 2008
.SHORT TERM...VALID FOR TDY AND SAT...
SMALL UPDATE TO ZFP AND WRKAFP THIS MORNING. BAND OF SNOW ON RADAR
AND IN SURFACE OBSERVATIONS WAS LOCATED FROM NEAR RED LODGE TO NW
ROSEBUD COUNTY. BAND WAS ASSOCIATED WITH AREA OF ISENTROPIC LIFT AND
LIFT FROM SHORTWAVE ROTATING AROUND THE UPPER LOW. HAVE SPREAD
HIGHER QPF AMOUNTS NE IN THE BAND AND RAISED SNOWFALL RATIOS IN THE
HIGHER TERRAIN AROUND KBIL AND IN AREAS WEST OF KBIL THAT WERE NOT
IN THE FOOTHILLS OR MOUNTAINS. REPORTS FROM AREA SPOTTERS AND SNOTEL
OBSERVATIONS INDICATED THAT AROUND 4 INCHES OF SNOW OCCURRED
OVERNIGHT IN HIGHER SPOTS NW AND SW OF KBIL INCLUDING
LAVINA...ROUNDUP...COLUMBUS AND ABSAROKEE. BETWEEN 2 AND 5 INCHES
OCCURRED IN THE BEARTOOTH/ABSAROKA MOUNTAINS AND 2 TO 4 INCHES WERE
REPORTED IN THE NE BIG HORNS. JUST A COUPLE INCHES FELL OVER THE
CRAZY MOUNTAINS. OVERALL...THE SNOW HAS BEEN QUITE WET WITH SNOWFALL
RATIOS 10 TO 1 OR MUCH LESS. MODELS UNDERFORECAST THE QPF LAST
NIGHT. NEW WRF SHOWED SHORTWAVE ENERGY WILL CONTINUE TO WRAP AROUND
THE UPPER LOW INTO THE REGION THIS AFTERNOON AND ISENTROPIC LIFT
WILL CONTINUE AS WELL. MID LEVELS WILL COOL THROUGH THE DAY CENTRAL
AND W. SNOW WILL CONTINUE OVER THE AREA...EXCEPT OVER THE NE ZONES
WHERE SOUNDINGS SHOWED LOW LEVELS SUPPORTED A MIX OF RAIN AND SNOW
WHICH HAS BEEN OCCURRING AT KBHK AND KMLS. THE DENDRITIC GROWTH
LAYER WILL REMAIN FAIRLY HIGH TODAY...BUT THE WAVES OF ENERGY AND
ISENTROPIC LIFT WILL MAKE SNOWFALL RATES HEAVIER AT TIMES. EXPECT
SEVERAL INCHES OF SNOW THIS AFTERNOON W AND S OF KBIL WITH 1 TO 2
INCHES FROM KBIL E. NO CHANGES TO THE WINTER STORM WARNINGS IN
EFFECT. NUDGED TEMPERATURES DOWN IN A FEW AREAS BASED ON OBSERVATION
TRENDS. ARTHUR
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
MODELS CONTINUE TO BE QUITE CONSISTENT REGARDING THE WINTER STORM
SYSTEM. STORM IMPACT WILL CONTINUE THROUGH SUNDAY AS WRAP AROUND
PRECIPITATION REMAINS ENTRENCHED ACROSS THE REGION. CURRENT TRACK
OF LOW MOVING ACROSS THE EASTERN ZONES SEEM TO SPREAD PRECIPITATION
ACROSS THE CWA...BUT BEST SNOW CHANCES LOOK LIKE THE AREA WEST OF
A LINE FROM KSHR TO KBIL TO ROUNDUP RESULTING IN AN ADDITIONAL 2
OR 3 INCHES OF SNOWFALL INTO SUNDAY NIGHT. SOME SNOW SHOWERS WILL
LINGER INTO MONDAY MORNING...BUT WILL PROVIDE LITTLE OR NO ADDITIONAL
ACCUMULATION.
THE WEATHER TURNS WARMER AND APPEARS QUITE DRY FOLLOWING THE PASSAGE OF
THE STORM SYSTEM...AS THE PATTERN BECOMES ZONAL AND DOWNSLOPE FLOW COMES
INTO PLAY. TEMPS WILL CLIMB FROM 40S MONDAY...STAYING COOL DUE TO
EXPECTED SNOW COVER...TO THE 60S ON FRIDAY. GILSTAD
&&
.AVIATION...
A DEVELOPING WINTER STORM WILL KEEP WIDESPREAD LIFR CONDITIONS
ACROSS THE AREA THROUGH SUNDAY. AREAS OF HEAVIER SNOW WILL PRODUCE
VLIFR CONDITIONS AT TIMES. BORSUM
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SAT SUN MON TUE WED THU
-------------------------------------------------------
BIL 034 026/033 026/034 023/040 028/053 032/053 033/054
+/S ++/S +8/S 31/B 10/B 11/B 11/B
LVM 034 020/032 020/036 022/043 027/053 032/053 033/054
+/S ++/S +8/S 31/N 10/B 11/B 21/B
HDN 034 025/034 026/038 022/043 027/054 031/054 032/055
+/S ++/S +8/S 31/B 10/B 11/B 11/B
MLS 036 026/037 026/038 024/043 029/055 032/055 033/056
+/O 89/S +7/S 31/B 11/B 11/B 21/U
4BQ 035 026/035 025/037 023/043 028/055 030/055 031/056
+/S ++/S +6/S 31/B 10/U 11/U 21/B
BHK 036 025/035 025/039 022/042 024/053 029/053 031/054
+/O 78/S +5/O 31/B 11/B 11/B 21/B
SHR 035 023/034 026/035 022/042 027/053 029/053 031/054
+/S ++/S +8/S 31/B 10/U 11/U 12/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 28>42-56>58-63>68.
WY...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KMSO 101516
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
916 AM MDT FRI OCT 10 2008
.DISCUSSION...WIDESPREAD LARGE SCALE LIFT CONTINUES ACROSS NORTH
CENTRAL IDAHO AND SOUTHWEST MONTANA THIS MORNING. HOWEVER...THERE
IS STILL SOME DRY AIR RESIDING IN MANY OF THE VALLEYS...AND THE
MAJORITY OF THE SNOW ACCUMULATION HAS BEEN IN THE MOUNTAINS OF
SOUTHWEST MONTANA. IN THESE LOCATIONS THERE HAVE BEEN SOME 5 TO 12
INCH SNOW REPORTS. DEPARTMENT OF TRANSPORTATION CAMERAS AT THE
PASSES IN THE AREA APPEAR TO SHOW 2 TO 4 INCHES OF SNOW THUS FAR.
THE SYNOPTIC LIFT IS EXPECTED TO BEGIN TO MOVE SLOWLY SOUTH AND
EAST THIS AFTERNOON...BUT PERSIST OVER SOUTHWEST MONTANA AND LEMHI
COUNTY THROUGH THE NIGHT AND SATURDAY. THEREFORE...WILL LEAVE THE
WINTER HIGHLIGHTS IN PLACE. BEST ACCUMULATIONS WILL CONTINUE IN
THE MOUNTAINS AND OVER THE PASSES...BUT WITH THE PROLONGED
LIFT...THE VALLEYS AROUND BUTTE AS WELL AS ROUTE 28 IN THE LEADORE
AREA OF LEMHI COUNTY....WILL BE IMPACTED AS WELL.
&&
.AVIATION...CLOUDS/SNOWFALL WILL REDUCE VISIBILITIES AND CEILINGS
ACROSS MUCH OF WEST-CENTRAL MONTANA AND LEMHI COUNTY TODAY AND
TONIGHT. MOUNTAINS AND PASSES WILL BE OBSCURED IN THESE AREAS. IN
GENERAL...CONDITIONS WILL BE IMPROVED FARTHER NORTH ACROSS
NORTHWEST MONTANA WITH ONLY MOUNTAIN TOPS MASKED BY CLOUDS AND
LIGHT PRECIPITATION TODAY.
&&
.PREV DISCUSSION... /ISSUED 409 AM MDT FRI OCT 10 2008/
DISCUSSION...A COLD MOIST AIR MASS RESIDES OVER MUCH OF WESTERN
MONTANA AND NORTH-CENTRAL IDAHO FOLLOWING THE DEVELOPMENT OF A
CLOSED UPPER LOW OVER IDAHO. ENHANCEMENT OF CLOUDS AND PRECIP
CONTINUES TO OCCUR ACROSS WEST-CENTRAL MONTANA AND LEMHI COUNTY
THIS MORNING AS MOISTURE CIRCULATES INTO THE SAME AREAS WHERE
BETTER SYNOPTIC LIFT/FORCING WAS TAKING PLACE. WEATHER RADAR AND
SURFACE OBSERVATIONS INDICATE LIGHT SNOW OCCURRING OVER THE HIGHER
TERRAIN WITH SOME VALLEY LOCATIONS PICKING UP SNOW ALSO. A TIGHT
NORTHERLY SURFACE PRESSURE GRADIENT COUPLED WITH HEALTHY NORTHEAST
WINDS ALOFT WILL RESULT IN BREEZY CONDITIONS. THE UPPER LOW SYSTEM
AND BULK OF ITS ASSOCIATED MOISTURE/DYNAMICS WILL SAG SOUTH
SLIGHTLY TONIGHT...SAGGING BETTER SNOWFALL SOUTH OVER EASTERN LEMHI
COUNTY. HOWEVER...AS THE LOW SYSTEM TRACKS NORTHEAST AGAIN THROUGH
EASTERN IDAHO ON SATURDAY...THIS WILL PUSH BETTER MOISTURE AND
DYNAMICS BACK NORTH INTO SOUTHWEST MONTANA...INCLUDING THE BUTTE
AREA. NORTHERLY WINDS WILL CONTINUE THROUGH SATURDAY CAUSING SOME
BLOWING AND DRIFTING OF SNOW. NO CHANGES MADE TO THE WINTER
HIGHLIGHTS (BELOW). WHILE THE BEST PRECIPITATION ASSOCIATED WITH
THIS PATTERN REMAINS FOCUSED OVER EASTERN LEMHI COUNTY AND
SOUTHWEST MONTANA...CONDITIONS GRADUALLY DRY AS YOU MOVE FARTHER
NORTH AWAY FROM THE LOW SYSTEM.
MONDAY THROUGH THURSDAY...NO CHANGES MADE TO THE FORECAST DURING
THIS PERIOD. AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL DRY AND
WARM CONDITIONS MONDAY. THE UPPER RIDGE WEAKENS TUESDAY IN
RESPONSE TO A DISTURBANCE MOVING INTO THE PACIFIC NORTHWEST. LOW
CHANCES OF PRECIPITATION WILL BE INTRODUCED BACK INTO THE
FORECAST TUESDAY AND WEDNESDAY AS THE AFFECTS OF THIS NEXT
DISTURBANCE SWEEPS ACROSS THE REGION.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL 6 PM MDT SATURDAY FOR BUTTE/BLACKFOOT
REGION.
WINTER WEATHER ADVISORY UNTIL NOON MDT TODAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER STORM WARNING UNTIL 6 PM MDT SATURDAY FOR EASTERN LEMHI
COUNTY.
&&
$$
UPDATE...WHITMORE
PREVIOUS DISCUSSION...MSJ
AVIATION...MSJ
000
FXUS65 KTFX 101516
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
916 AM MDT FRI OCT 10 2008
.UPDATE...EARLY SEASON WINTER STORM CONTINUES TO BUILD STRENGTH
ACROSS THE REGION THIS MORNING. LOOKS LIKE YESTERDAYS MODELS
TOOK THE PRECIPITATION TOO FAR TO THE NORTHWEST IN CENTRAL MONTANA
AS MY SOUTHERN AND SOUTHEAST ZONES ARE CURRENTLY TAKING THE BRUNT
OF THE STORM. HAVE HAD REPORTS OF 8 INCHES ACCUMULATION NEAR GRANT
IN BEAVERHEAD COUNTY...AND 5 INCHES AT HALF MOON PASS ON THE EAST
SIDE OF THE BIG SNOWY MOUNTAINS IN FERGUS COUNTY. MAIN CHANGE IN
THE UPDATE WAS TO LOWER POPS OVER MY NORTHERN PLAINS...INCLUDING
AT GREAT FALLS WHERE POPS FOR TODAY HAVE BEEN DROPPED DOWN TO A
CHANCE ONLY. THE WARNING WILL CONTINUE FOR ALL OF SOUTHWEST
MONTANA AND THE SOUTHERN PORTION OF CENTRAL MONTANA. ONLY OTHER
CHANGE TO THE FORECAST WERE SOME MINOR TWEAKS TO TEMPERATURES AND
TO SLIGHTLY ADJUST SNOW LEVELS AND SUBSEQUENT PRECIPITATION TYPE.
MPJ
&&
.AVIATION...
UPDATED 1145Z.
A DEEP UPPER LEVEL LOW PRESSURE TROF WILL REMAIN OVER THE AREA AND
KEEP THE AIRMASS COOL AND MOIST. PERIODS OF SNOW AND LOW CIGS WILL
CAUSE AREAS OF MVFR CONDITIONS ACROSS SOUTHWEST MONTANA AND PORTIONS
OF NORTH CENTRAL MONTANA. VFR CONDITIONS WILL PREVAIL OVER MUCH OF
NORTH CENTRAL MONTANA AND THE CANADIAN BORDER ALTHOUGH MVFR
CONDITIONS MAY DEVELOP AFTER 06Z FRIDAY. SURFACE FLOW WILL GENERALLY
REMAIN NORTHEAST AND BREEZY.
&&
.PREV DISCUSSION...
/ISSUED 548 AM MDT FRI OCT 10 2008/
TODAY THROUGH SUNDAY...AN UPPER LEVEL LOW OVER SOUTHERN IDAHO...WILL
CONTINUE TO DEEPEN THROUGH THE DAY...WITH MOST DYNAMICS WELL SOUTH
OF MONTANA. HOWEVER...ABUNDANT MOISTURE WILL MOVE NORTHWARD INTO
THE REGION THROUGH THE WEEKEND. A GOOD UPSLOPE SURFACE PATTERN WILL
CONTINUES EAST OF THE DIVIDE THROUGH SUNDAY...BETWEEN A DEEPENING
SURFACE LOW OVER UTAH AND A CANADIAN SURFACE HIGH OVER CENTRAL
ALBERTA. THUS...A WINTER STORM WARNING WILL REMAIN TODAY THROUGH
SUNDAY AFTERNOON FOR MOST OF SOUTHWEST MONTANA AND THE SOUTHERN HALF
OF NORTH CENTRAL MONTANA. SNOW IS EXPECTED TO BE HEAVY AT TIMES WITH
ACCUMULATIONS OF 15 TO 30 INCHES OVER THE MOUNTAINS AND
3 TO 6 INCHES ACROSS THE PLAINS AND VALLEYS BY SUNDAY EVENING.
THERE WILL BE SOME MELTING OF SNOW...DUE TO WARM GROUND...AT LOWER
ELEVATIONS. THE BEST CHANCE FOR HEAVY SNOW WILL BE SATURDAY AFTERNOON
AND SATURDAY NIGHT...AS THE UPPER LOW MOVES NORTHEAST INTO SOUTHEAST
MONTANA BY SUNDAY EVENING. IT WILL BE UNSEASONABLY COLD THROUGH
SUNDAY...WITH TEMPERATURES RUNNING SOME 20 TO 30 DEGREES BELOW
SEASONAL AVERAGE. HIGHWAYS WILL BECOME ICY AT LOWER
ELEVATIONS...ESPECIALLY DURING THE NIGHT AND MORNING HOURS ALONG
WITH SOME BLOWING SNOW THROUGH THE PASSES AND CANYONS. CONDITIONS
WILL IMPROVE FROM THE NORTHWEST AS AN UPPER LEVEL RIDGE OF HIGH
PRESSURE OVER THE WEST COAST...BUILDS INTO CENTRAL ALBERTA.
WILLIAMSON DC
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 37 23 34 21 / 30 60 60 40
CTB 39 21 34 17 / 20 30 30 10
HLN 40 25 34 25 / 60 60 50 50
BZN 40 26 36 25 / 100 80 80 80
WEY 33 19 30 16 / 90 90 80 80
DLN 34 20 30 17 / 80 60 50 80
HVR 45 25 39 18 / 20 30 30 10
LWT 36 22 30 17 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM MDT SUNDAY FOR MTZ008-012-014-
015-050>055.
&&
$$
SHORT TERM...MPJ/WILLIAMSON DC
LONG TERM...ZELZER/SAUCIER
AVIATION...ZELZER
WEATHER.GOV/GREATFALLS
000
FXUS65 KTFX 101148
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
548 AM MDT FRI OCT 10 2008
.DISCUSSION...
TODAY THROUGH SUNDAY...AN UPPER LEVEL LOW OVER SOUTHERN IDAHO...WILL
CONTINUE TO DEEPEN THROUGH THE DAY...WITH MOST DYNAMICS WELL SOUTH
OF MONTANA. HOWEVER...ABUNDANT MOISTURE WILL MOVE NORTHWARD INTO
THE REGION THROUGH THE WEEKEND. A GOOD UPSLOPE SURFACE PATTERN WILL
CONTINUES EAST OF THE DIVIDE THROUGH SUNDAY...BETWEEN A DEEPENING
SURFACE LOW OVER UTAH AND A CANADIAN SURFACE HIGH OVER CENTRAL
ALBERTA. THUS...A WINTER STORM WARNING WILL REMAIN TODAY THROUGH
SUNDAY AFTERNOON FOR MOST OF SOUTHWEST MONTANA AND THE SOUTHERN HALF
OF NORTH CENTRAL MONTANA. SNOW IS EXPECTED TO BE HEAVY AT TIMES WITH
ACCUMULATIONS OF 15 TO 30 INCHES OVER THE MOUNTAINS AND
3 TO 6 INCHES ACROSS THE PLAINS AND VALLEYS BY SUNDAY EVENING.
THERE WILL BE SOME MELTING OF SNOW...DUE TO WARM GROUND...AT LOWER
ELEVATIONS. THE BEST CHANCE FOR HEAVY SNOW WILL BE SATURDAY AFTERNOON
AND SATURDAY NIGHT...AS THE UPPER LOW MOVES NORTHEAST INTO SOUTHEAST
MONTANA BY SUNDAY EVENING. IT WILL BE UNSEASONABLY COLD THROUGH
SUNDAY...WITH TEMPERATURES RUNNING SOME 20 TO 30 DEGREES BELOW
SEASONAL AVERAGE. HIGHWAYS WILL BECOME ICY AT LOWER
ELEVATIONS...ESPECIALLY DURING THE NIGHT AND MORNING HOURS ALONG
WITH SOME BLOWING SNOW THROUGH THE PASSES AND CANYONS. CONDITIONS
WILL IMPROVE FROM THE NORTHWEST AS AN UPPER LEVEL RIDGE OF HIGH
PRESSURE OVER THE WEST COAST...BUILDS INTO CENTRAL ALBERTA.
WILLIAMSON DC
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.AVIATION...
UPDATED 1145Z.
A DEEP UPPER LEVEL LOW PRESSURE TROF WILL REMAIN OVER THE AREA AND
KEEP THE AIRMASS COOL AND MOIST. PERIODS OF SNOW AND LOW CIGS WILL
CAUSE AREAS OF MVFR CONDITIONS ACROSS SOUTHWEST MONTANA AND PORTIONS
OF NORTH CENTRAL MONTANA. VFR CONDITIONS WILL PREVAIL OVER MUCH OF
NORTH CENTRAL MONTANA AND THE CANADIAN BORDER ALTHOUGH MVFR
CONDITIONS MAY DEVELOP AFTER 06Z FRIDAY. SURFACE FLOW WILL GENERALLY
REMAIN NORTHEAST AND BREEZY.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 34 23 34 21 / 60 60 60 40
CTB 38 21 34 17 / 30 30 30 10
HLN 38 25 34 25 / 60 60 50 50
BZN 38 26 36 25 / 100 80 80 80
WEY 33 19 30 16 / 90 90 80 80
DLN 33 20 30 17 / 80 60 50 80
HVR 44 25 39 18 / 20 30 30 10
LWT 34 22 30 17 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM MDT SUNDAY FOR MTZ008-012-014-
015-050>055.
&&
$$
SHORT TERM...WILLIAMSON DC
LONG TERM...ZELZER/SAUCIER
AVIATION...ZELZER
WEATHER.GOV/GREATFALLS
000
FXUS65 KGGW 101017
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
417 AM MDT FRI OCT 10 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SUNDAY...
UPPER TROUGH DIGGING INTO THE GREAT BASIN WILL CONTINUE TO BRING
SOUTHWEST FLOW ALOFT TO MONTANA TODAY AND TONIGHT. MOISTURE
OVERRUNNING A FRONTAL BOUNDARY WELL SOUTH OF MONTANA HAS BROUGHT A
MIX OF RAIN AND SNOW TO SOUTHEAST MONTANA OVERNIGHT. THE
PRECIPITATION IS GENERALLY SOUTH OF WINNETT... JORDAN AND GLENDIVE
AT 10Z. THE PRECIPITATION WILL MAKE MINIMAL PROGRESS FURTHER NORTH
TODAY AS LOW LEVEL DRY AIR FROM THE NORTH KEEPS THE RAIN AND SNOW
SOUTH OF THE MISSOURI RIVER. WITH TEMPERATURES NEAR FREEZING AT
HIGHER ELEVATION SITES LIKE BIG SHEEP MOUNTAIN RAWS...WILL KEEP
WINTER STORM WARNING IN PLACE AS WET HEAVY SNOW IS STILL LIKELY IN
HIGHER ELEVATION AREAS.
THE OVERRUNNING MOISTURE WILL MOVE TO THE EAST THIS EVENING
ALLOWING A BREAK IN THE PRECIPITATION TONIGHT. MEANWHILE...A
CLOSED UPPER LOW WILL FORM AT THE BASE ON THE UPPER TROUGH OVER
NEVADA TODAY AND DEEPEN AS IT MOVES SLOWLY NORTHEAST TONIGHT AND
SATURDAY.
THE NEXT SURGE OF MOISTURE WILL MOVE NORTH SATURDAY AND WITH
TEMPERATURES COLD ENOUGH ALOFT...WIDESPREAD SNOW WILL DEVELOP FROM
SOUTH TO NORTH ACROSS NORTHEAST MONTANA SATURDAY AFTERNOON AND EVENING.
THE UPPER LOW WILL LIFT NORTHEAST ACROSS EASTERN MONTANA ON
SUNDAY. WITH GULF OF MEXICO MOISTURE FEEDING THIS SYSTEM...HEAVY
SNOW IS LIKELY ACROSS MOST OF NORTHEAST MONTANA SATURDAY NIGHT AND
SUNDAY. WILL MAINTAIN GOING WINTER STORM WATCH FOR NOW. NORTH
WINDS 15 TO 30 MPH WILL BLOW AND DRIFT ANY OF THE SNOW THAT FALLS.
FORECAST MODELS ARE HINTING AT A FOOT OR MORE OF SNOW FOR PARTS OF
THE FORECAST AREA FROM THIS STORM. FORRESTER
PREVIOUS SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH
SATURDAY...A BUSY FEW DAYS...WEATHER WISE...IN STORE FOR NORTHEAST
MONTANA. AN UPPER TROUGH DIGGING INTO THE GREAT BASIN WILL EJECT
WARMER MORE MOIST AIR OVER A POLAR AIRMASS IN PLACE OVER EASTERN
MONTANA. THIS OVERRUNNING WILL DRIVE A MIX OF RAIN AND SNOW ACROSS
THE SOUTHERN ZONES...MAINLY SOUTH OF HIGHWAY 200. HAVE UPGRADED
THE EXISTING WATCH FOR THE SOUTHERN ZONES TO A WINTER STORM
WARNING. NORTHERLY WINDS OF 15 TO 25 MPH WILL ACCOMPANY THE
STORM...HOWEVER GIVEN THE HEAVY WET NATURE TO THE SNOWFALL DO NOT
EXPECT MUCH IN THE WAY OF BLOWING AND DRIFTING. THESE WINDS MAY
ALSO REQUIRE A LAKE WIND ADVISORY FOR FORT PECK LAKE FRIDAY
AFTERNOON. BY FRIDAY EVENING THE LIFT GENERATED BY THE OVERRUNNING
WILL TAPER OFF...SUBSEQUENTLY TAPERING OFF THE RAIN AND SNOW. THIS
LULL WILL LAST INTO SATURDAY MORNING...BEFORE A SECOND MORE
POTENT/WET SYSTEM MOVES IN FROM THE SOUTH. COORDINATED A WATCH
WITH THE EXTENDED FORECASTER THAT STARTS SATURDAY AFTERNOON FOR
AREAS SOUTH OF THE MISSOURI RIVER. SIGNIFICANT SNOW ACCUMULATION
CAN BE EXPECTED ACROSS THE WHOLE OF NORTHEAST MONTANA WITH THIS
SECOND STORM SYSTEM. GILCHRIST
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
STORM VORTEX WILL BEGIN LIFTING OUT OF NORTHEAST MONTANA SUNDAY
NIGHT. WRAP-AROUND ENERGY FROM THE NORTHERLY FLOW ON THE WEST
SIDE OF THE LOW WILL FOCUS QPF OVER THE NORTHERN ZONES FOR
ADDITIONAL TAPERING OFF SNOWFALL. RISING HEIGHTS FROM THE WEST
MONDAY WILL CUT OFF ANY REMAINING PRECIPITATION. THE POSITIVE
LEANING RIDGE WILL BE QUICKLY FLATTENED BY A QUICK-MOVING
SHORTWAVE ACROSS ALBERTA AND SASKATCHEWAN MONDAY NIGHT. THE 00Z
GFS SHORTWAVE IS MORE SHALLOW THAN THE 12/00Z ECMWF SHORTWAVE.
TUESDAY AND WEDNESDAY THE MODELS SEND ADDITIONAL WEAK SHORTWAVES
ACROSS CANADA...NOT NECESSARILY IN AGREEMENT WITH EACH OTHER. BUT
AROUND WEDNESDAY NIGHT OR THURSDAY AN UPPER RIDGE SLOWLY BUILDS UP
OVER THE WEST...MAINTAINING UPPER FLOW FROM THE NORTHWEST LOCALLY.
AFTER THE PASSAGE OF THE SUNDAY NIGHT STORM THE CONDITIONS WILL
GENERALLY DRY AND COOL...WITH THE POSSIBILITY OF WARMING TO NORMAL
BY THE END OF THE PERIOD. SCT
&&
.AVIATION...
A STORM SYSTEM EJECTING RAIN AND SNOW NORTHEAST ACROSS EASTERN
MONTANA AND THE WESTERN DAKOTAS WILL CONTINUE TO LIFT NORTH TODAY
BRING MVFR CEILINGS AND VISIBILITIES. KGDV AND KSDY WILL BE
AFFECTED THE MOST WITH POSSIBLE IFR CONDITIONS FROM SNOW/LOW
CEILINGS. HIGH PRESSURE TO THE NORTH WILL RESULT IN LESSER AMOUNTS
OF RAIN AND SNOW AFFECTING KOLF AND KGGW. MORNING NORTHEAST WINDS
OF 10KT WILL INCREASE THIS AFTERNOON TO 15-25KT BEFORE DIMINISHING
AROUND SUNSET. SCT
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND
SOUTHERN VALLEY-DANIELS-SHERIDAN-WESTERN ROOSEVELT-NORTHERN
PHILLIPS-SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT.
WINTER STORM WARNING UNTIL 6 PM MDT THIS AFTERNOON FOR PETROLEUM-
GARFIELD-DAWSON-PRAIRIE-WIBAUX.
WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
AFTERNOON FOR PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-
WIBAUX.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KMSO 101009
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
409 AM MDT FRI OCT 10 2008
.DISCUSSION...A COLD MOIST AIR MASS RESIDES OVER MUCH OF WESTERN
MONTANA AND NORTH-CENTRAL IDAHO FOLLOWING THE DEVELOPMENT OF A
CLOSED UPPER LOW OVER IDAHO. ENHANCEMENT OF CLOUDS AND PRECIP
CONTINUES TO OCCUR ACROSS WEST-CENTRAL MONTANA AND LEMHI COUNTY
THIS MORNING AS MOISTURE CIRCULATES INTO THE SAME AREAS WHERE
BETTER SYNOPTIC LIFT/FORCING WAS TAKING PLACE. WEATHER RADAR AND
SURFACE OBSERVATIONS INDICATE LIGHT SNOW OCCURRING OVER THE HIGHER
TERRAIN WITH SOME VALLEY LOCATIONS PICKING UP SNOW ALSO. A TIGHT
NORTHERLY SURFACE PRESSURE GRADIENT COUPLED WITH HEALTHY NORTHEAST
WINDS ALOFT WILL RESULT IN BREEZY CONDITIONS. THE UPPER LOW SYSTEM
AND BULK OF ITS ASSOCIATED MOISTURE/DYNAMICS WILL SAG SOUTH
SLIGHTLY TONIGHT...SAGGING BETTER SNOWFALL SOUTH OVER EASTERN LEMHI
COUNTY. HOWEVER...AS THE LOW SYSTEM TRACKS NORTHEAST AGAIN THROUGH
EASTERN IDAHO ON SATURDAY...THIS WILL PUSH BETTER MOISTURE AND
DYNAMICS BACK NORTH INTO SOUTHWEST MONTANA...INCLUDING THE BUTTE
AREA. NORTHERLY WINDS WILL CONTINUE THROUGH SATURDAY CAUSING SOME
BLOWING AND DRIFTING OF SNOW. NO CHANGES MADE TO THE WINTER
HIGHLIGHTS (BELOW). WHILE THE BEST PRECIPITATION ASSOCIATED WITH
THIS PATTERN REMAINS FOCUSED OVER EASTERN LEMHI COUNTY AND
SOUTHWEST MONTANA...CONDITIONS GRADUALLY DRY AS YOU MOVE FARTHER
NORTH AWAY FROM THE LOW SYSTEM.
MONDAY THROUGH THURSDAY...NO CHANGES MADE TO THE FORECAST DURING
THIS PERIOD. AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL DRY AND
WARM CONDITIONS MONDAY. THE UPPER RIDGE WEAKENS TUESDAY IN
RESPONSE TO A DISTURBANCE MOVING INTO THE PACIFIC NORTHWEST. LOW
CHANCES OF PRECIPITATION WILL BE INTRODUCED BACK INTO THE
FORECAST TUESDAY AND WEDNESDAY AS THE AFFECTS OF THIS NEXT
DISTURBANCE SWEEPS ACROSS THE REGION.
&&
.AVIATION...CLOUDS/SNOWFALL WILL REDUCE VISIBILITIES AND CEILINGS
ACROSS MUCH OF WEST-CENTRAL MONTANA AND LEMHI COUNTY TODAY AND
TONIGHT. MOUNTAINS AND PASSES WILL BE OBSCURED IN THESE AREAS. IN
GENERAL...CONDITIONS WILL BE IMPROVED FARTHER NORTH ACROSS
NORTHWEST MONTANA WITH ONLY MOUNTAIN TOPS MASKED BY CLOUDS AND
LIGHT PRECIPITATION TODAY.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING UNTIL 6 PM MDT SATURDAY FOR BUTTE/BLACKFOOT
REGION.
WINTER WEATHER ADVISORY UNTIL NOON MDT TODAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER STORM WARNING UNTIL 6 PM MDT SATURDAY FOR EASTERN LEMHI
COUNTY.
&&
$$
MSJ
000
FXUS65 KTFX 100942
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
342 AM MDT FRI OCT 10 2008
.DISCUSSION...
TODAY THROUGH SUNDAY...AN UPPER LEVEL LOW OVER SOUTHERN IDAHO...WILL
CONTINUE TO DEEPEN THROUGH THE DAY...WITH MOST DYNAMICS WELL SOUTH
OF MONTANA. HOWEVER...ABUNDANT MOISTURE WILL MOVE NORTHWARD INTO
THE REGION THROUGH THE WEEKEND. A GOOD UPSLOPE SURFACE PATTERN WILL
CONTINUES EAST OF THE DIVIDE THROUGH SUNDAY...BETWEEN A DEEPENING
SURFACE LOW OVER UTAH AND A CANADIAN SURFACE HIGH OVER CENTRAL
ALBERTA. THUS...A WINTER STORM WARNING WILL REMAIN TODAY THROUGH
SUNDAY AFTERNOON FOR MOST OF SOUTHWEST MONTANA AND THE SOUTHERN HALF
OF NORTH CENTRAL MONTANA. SNOW IS EXPECTED TO BE HEAVY AT TIMES WITH
ACCUMULATIONS OF 15 TO 30 INCHES OVER THE MOUNTAINS AND
3 TO 6 INCHES ACROSS THE PLAINS AND VALLEYS BY SUNDAY EVENING.
THERE WILL BE SOME MELTING OF SNOW...DUE TO WARM GROUND...AT LOWER
ELEVATIONS. THE BEST CHANCE FOR HEAVY SNOW WILL BE SATURDAY AFTERNOON
AND SATURDAY NIGHT...AS THE UPPER LOW MOVES NORTHEAST INTO SOUTHEAST
MONTANA BY SUNDAY EVENING. IT WILL BE UNSEASONABLY COLD THROUGH
SUNDAY...WITH TEMPERATURES RUNNING SOME 20 TO 30 DEGREES BELOW
SEASONAL AVERAGE. HIGHWAYS WILL BECOME ICY AT LOWER
ELEVATIONS...ESPECIALLY DURING THE NIGHT AND MORNING HOURS ALONG
WITH SOME BLOWING SNOW THROUGH THE PASSES AND CANYONS. CONDITIONS
WILL IMPROVE FROM THE NORTHWEST AS AN UPPER LEVEL RIDGE OF HIGH
PRESSURE OVER THE WEST COAST...BUILDS INTO CENTRAL ALBERTA.
WILLIAMSON DC
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...A DEEP...UPPER LEVEL LOW
PRESSURE SYSTEM WILL CONTINUE TO MOVE SLOWLY EAST...MOVING ACROSS
THE MONTANA/DAKOTA BORDER SUNDAY NIGHT. HIGH PRESSURE WILL BUILD
ALOFT OVER THE ZONES AND THE THE AIRMASS WILL BEGIN A DRYING AND
WARMING TREND THAT WILL LAST INTO TUESDAY. AN UPPER LEVEL LOW
PRESSURE TROF WILL CROSS THE ROCKIES EARLY WEDNESDAY. THIS WILL BE A
RATHER FAST-MOVING SYSTEM AND THE CHANCE OF PRECIPITATION WILL
REMAIN LOW. HOWEVER...BREEZY CONDITIONS WILL REMAIN OVER THE AREA
UNTIL THIS SHORT WAVE MOVES INTO EASTERN MONTANA. THE WARMING TREND
WILL ALSO BE INTERRUPTED UNTIL ANOTHER HIGH PRESSURE RIDGE BEGINS TO
BUILD OVER THE AREA ON THURSDAY. ZELZER
THURSDAY AND FRIDAY...A DISTURBANCE IN A NORTHWEST FLOW MOVES EAST
OUT OF THE ZONES THURSDAY ALLOWING HIGH PRESSURE TO BUILD IN FROM
THE WEST. A ZONAL FLOW SETS UP AHEAD OF THE NEXT PACIFIC SYSTEM BY
FRIDAY. SAUCIER
&&
.AVIATION...
UPDATED 0455Z.
AN UPPER LEVEL TROUGH WILL CONTINUE TO DEEPEN OVER THE PACIFIC
NORTHWEST AND INTO THE GREAT BASIN THROUGH 06Z SATURDAY. THE MOIST
EASTERLY FLOW ALOFT WILL KEEP WIDESPREAD CLOUDINESS WITH SNOW OVER
CENTRAL (KGTF AND KLWT) AND SOUTHWEST (KHLN AND KBZN) MONTANA.
CONDITIONS THERE WILL REMAIN IN THE LOW VFR/HIGH MVFR RANGE WITH
MOUNTAIN OBSCURATION. HOWEVER...CONDITIONS OVERNIGHT AND THROUGH THE
EARLY MORNING MAY LOWER TO IFR LEVELS AT TIMES DUE TO CLOUDS AND
SNOW. ONLY MID AND HIGH CLOUDS WILL LINGER OVER NORTH CENTRAL
MONTANA (KCTB AND KHVR TERMINALS) THROUGH FRIDAY...BUT A FEW SHOWERS
MAY DEVELOP THERE FRIDAY EVENING. OVERALL...SURFACE WINDS WILL
GENERALLY REMAIN NORTHEASTERLY AND BREEZY. COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 34 23 34 21 / 60 60 60 40
CTB 38 21 34 17 / 30 30 30 10
HLN 38 25 34 25 / 60 60 50 50
BZN 38 26 36 25 / 100 80 80 80
WEY 33 19 30 16 / 90 90 80 80
DLN 33 20 30 17 / 80 60 50 80
HVR 44 25 39 18 / 20 30 30 10
LWT 34 22 30 17 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM MDT SUNDAY FOR MTZ008-012-014-
015-050>055.
&&
$$
SHORT TERM...WILLIAMSON DC
LONG TERM...ZELZER/SAUCIER
AVIATION...ZELZER
WEATHER.GOV/GREATFALLS
000
FXUS65 KBYZ 100922
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
322 AM MDT FRI OCT 10 2008
.SHORT TERM...VALID FOR TDY AND SAT...
OVERALL PICTURE OF THE FORECAST IN TACT AND DID NOT CHANGE MUCH
OF. SNOW AND/OR RAIN AND SNOW HAVE BEEN OCCURRING ALL NIGHT OVER
A LARGE PART OF THE AREA. PRECIPITATION HAS BEEN PRIMARILY SNOW
OVER CENTRAL AND WESTERN ZONES...WITH RAIN OR A RAIN AND SNOW
MIXTURE OVER PARTS OF THE EAST. HIGHER ELEVATIONS HAVE ALREADY
ACCUMULATED SEVERAL INCHES BASED ON SNOTEL REPORTS. WARM GROUND
TEMPERATURES HAVE LIMITED ACCUMULATIONS A BIT OVER THE PLAINS.
SNOW ACCUMULATIONS SEEM TO BE ELEVATION DEPENDANT...WITH AREAS
ABOVE 35 HUNDRED FEET GETTING SNOW TO STICK...BUT THOSE BELOW
HAVING A HARDER TIME. BURSTS OF HEAVIER SNOW OVERCOMES THE WARMER
GROUND. STRONG AND DEEP ISENTROPIC LIFT SHOULD ALLOW FOR A
CONTINUATION OF THE SNOW TODAY. THIS DEEP LIFT WILL BE ENHANCED
BY SHORTWAVES EJECTING OUT OF DEEPENING UPPER LOW OVER NORTHEAST
NEVADA. ONE SUCH WAVE WAS MOVING OVER SOUTH CENTRAL MONTANA AT
THE MOMENT AND THE RADAR DATA WAS FILLING IN AGAIN. SHOULD SEE
SNOW ALL MORNING...WITH PERIODS OF MODERATE SNOW EARLY. THE NEXT
SHORTWAVE TO ENTER THE AREA BY LATE MORNING WAS MOVING INTO
SOUTHWEST WYOMING THIS HOUR. THIS WAVE WILL ENHANCE THE STRONG
LIFT AGAIN BY LATE MORNING AND CONTINUE THE LIFT INTO EARLY
EVENING. HOW MUCH SNOW ACCUMULATES OVER THE PLAINS WILL BE VERY
TRICKY AS GROUND STILL FAIRLY WARM AND EARLY OCTOBER SUN
ANGLE...NOT TO MENTION WET SNOW...CAN LIMIT ACCUMULATIONS. A
LAYER OF SNOW THIS MORNING WOULD HELP TO NOT HINDER
ACCUMULATIONS. WILL CARRY CURRENT ACCUMULATIONS.
THE DEEP UPPER LOW DIGS INTO SOUTHERN NEVADA TONIGHT AND THE
SHORTWAVE ENERGY OF THIS AFTERNOON LIFTS NORTH. THIS SHOULD TAPER
SNOW OFF A BIT TONIGHT...BUT NOT TOTALLY. SNOW RATES MAY BE AS
STRONG BUT COOLING TEMPERATURES SHOULD ALLOW FOR EASIER
ACCUMULATIONS. ISENTROPIC LIFT WILL CONTINUE TONIGHT AND THUS
SNOW WILL LIKELY ACCUMULATE FURTHER. THE UPPER LOW OVER NEVADA
THEN EJECTS INTO UTAH SATURDAY. THIS WILL SEND A STRONG SURGE OF
UPPER DIFLUENCE INTO SOUTHERN MONTANA AND NORTHERN WYOMING. THIS
POWERFUL FORCING WILL CONTINUE THROUGH EARLY SUNDAY AS THE LOW
MOVES TOWARD SOUTHEAST MONTANA. THIS LOOKS TO BE THE BEST
POTENTIAL FOR HEAVY SNOW ACROSS THE AREA. TIMING MAY BE SLOWED
FURTHER AS THE LOW CONTINUES TO EVOLVE. BUMPED ACCUMULATIONS UP A
BIT MORE SATURDAY NIGHT. MODELS HAVE BEEN CONSISTENTLY PUSHING
DYNAMIC FORCING INTO SOUTHEAST MONTANA SATURDAY NIGHT AND HAVE
BUMPED ACCUMULATIONS THERE AS WELL. SNOW TOTALS FOR SATURDAY
NIGHT ALONE SHOULD APPROACH 6 INCHES IN BILLINGS AND COULD REACH
A FOOT OVER SOUTHEAST MONTANA. THE FAVORED UPSLOPE AREAS WILL
ALSO BE HIT VERY HARD BY THIS STORM AS UPSLOPE WILL BE VERY DEEP.
RED LODGE LOOKS TO BE IN LINE TO GET NEARLY 2 FEET OF SNOW BY THE
TIME IT ENDS SUNDAY NIGHT. THE MOUNTAINS WILL GET SEVERAL FEET OF
NEW SNOW FROM THIS STORM AS WELL. WILL KEEP THE HIGHLIGHTS GOING.
THIS DANGEROUS SITUATION WILL STRETCH OUT FOR SEVERAL DAYS. A
MAJORITY OF THE LEAVES HAVE NOT DROPPED YET AND HEAVY WET SNOW
COULD EASILY TAKE TREE LIMBS DOWN...THUS RUNNING A GREAT RISK OF
EXTENSIVE POWER OUTAGES AS THE SNOW ACCUMULATES. HUMPHREY
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
MODELS CONTINUE TO BE QUITE CONSISTENT REGARDING THE WINTER STORM
SYSTEM. STORM IMPACT WILL CONTINUE THROUGH SUNDAY AS WRAP AROUND
PRECIPITATION REMAINS ENTRENCHED ACROSS THE REGION. CURRENT TRACK
OF LOW MOVING ACROSS THE EASTERN ZONES SEEM TO SPREAD PRECIPITATION
ACROSS THE CWA...BUT BEST SNOW CHANCES LOOK LIKE THE AREA WEST OF
A LINE FROM KSHR TO KBIL TO ROUNDUP RESULTING IN AN ADDITIONAL 2
OR 3 INCHES OF SNOWFALL INTO SUNDAY NIGHT. SOME SNOW SHOWERS WILL
LINGER INTO MONDAY MORNING...BUT WILL PROVIDE LITTLE OR NO ADDITIONAL
ACCUMULATION.
THE WEATHER TURNS WARMER AND APPEARS QUITE DRY FOLLOWING THE PASSAGE OF
THE STORM SYSTEM...AS THE PATTERN BECOMES ZONAL AND DOWNSLOPE FLOW COMES
INTO PLAY. TEMPS WILL CLIMB FROM 40S MONDAY...STAYING COOL DUE TO
EXPECTED SNOW COVER...TO THE 60S ON FRIDAY. GILSTAD
&&
.AVIATION...
RAIN AND SNOW MIX OF SHOWERS...OF VARYING INTENSITY...WILL
CONTINUE THROUGH THE DAY TODAY. RAIN WILL BE MIXED WITH THE SNOW
AT TIMES THROUGH THE DAY...HIGHER TERRAIN WILL SEE SNOW THROUGH
THE DAY. LOW CEILINGS ARE EXPECTED TO REMAIN IN PLACE THROUGH THE
DAY AND OVERNIGHT...RESULTING IN FLIGHT CONDITIONS RANGING FROM
IFR TO VLIFR ACROSS THE REGION. THE MOUNTAINS WILL BE OBSCURED
THOUGH SUNDAY NIGHT. GILSTAD
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SAT SUN MON TUE WED THU
-------------------------------------------------------
BIL 034 026/033 026/034 023/043 028/053 032/053 033/054
+/S ++/S +8/S 31/B 10/B 11/B 11/B
LVM 034 020/032 020/036 022/046 027/053 032/053 033/054
+/S ++/S +8/S 31/N 10/B 11/B 21/B
HDN 037 025/034 026/038 022/046 027/054 031/054 032/055
+/S ++/S +8/S 31/B 10/B 11/B 11/B
MLS 039 026/037 026/038 024/046 029/055 032/055 033/056
+/O 89/S +7/S 31/B 11/B 11/B 21/U
4BQ 035 026/035 025/037 023/046 028/055 030/055 031/056
+/S ++/S +6/S 31/B 10/U 11/U 21/B
BHK 037 025/035 025/039 022/045 024/053 029/053 031/054
+/S 78/S +5/O 31/B 11/B 11/B 21/B
SHR 035 023/034 026/035 022/045 027/053 029/053 031/054
+/S ++/S +8/S 31/B 10/U 11/U 12/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 28>42-56>58-63>68.
WY...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 100504
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MDT THU OCT 9 2008
...UPDATE TO AVIATION...
.DISCUSSION...
UPDATE FORTHCOMING. HAVE MADE RELATIVELY MINOR ADJUSTMENTS TO THE
POP GRIDS TONIGHT MAINLY TO BETTER ALIGN WITH NEIGHBORING OFFICES.
FIRST SIGNIFICANT WINTER STORM OF THE SEASON CONTINUES TO DEVELOP
OVER THE AREA. DEEP UPPER TROF SLOWLY MOVES OVER THE AREA FRIDAY.
OVERRUNNING PRECIPITATION...MAINLY SNOW...STILL LOOKING GOOD THROUGH
THE WEEKEND. EMANUEL
&&
.AVIATION...
UPDATED 0455Z.
AN UPPER LEVEL TROUGH WILL CONTINUE TO DEEPEN OVER THE PACIFIC
NORTHWEST AND INTO THE GREAT BASIN THROUGH 06Z SATURDAY. THE MOIST
EASTERLY FLOW ALOFT WILL KEEP WIDESPREAD CLOUDINESS WITH SNOW OVER
CENTRAL (KGTF AND KLWT) AND SOUTHWEST (KHLN AND KBZN) MONTANA.
CONDITIONS THERE WILL REMAIN IN THE LOW VFR/HIGH MVFR RANGE WITH
MOUNTAIN OBSCURATION. HOWEVER...CONDITIONS OVERNIGHT AND THROUGH THE
EARLY MORNING MAY LOWER TO IFR LEVELS AT TIMES DUE TO CLOUDS AND
SNOW. ONLY MID AND HIGH CLOUDS WILL LINGER OVER NORTH CENTRAL
MONTANA (KCTB AND KHVR TERMINALS) THROUGH FRIDAY...BUT A FEW SHOWERS
MAY DEVELOP THERE FRIDAY EVENING. OVERALL...SURFACE WINDS WILL
GENERALLY REMAIN NORTHEASTERLY AND BREEZY. COULSTON
&&
.PREV DISCUSSION...ISSUED 242 PM MDT THU OCT 9 2008
TONIGHT THROUGH SUNDAY...FORECAST AREA IS BENEATH THE INFLUENCE
OF A DEVELOPING UPPER LEVEL TROUGH. FORECAST CONTINUES TO LOOK
FAVORABLE FOR THE DEVELOPMENT OF A SIGNIFICANT EARLY SEASON WINTER
STORM. SHOWERS ARE ALREADY DEVELOPING ACROSS SOUTHERN PORTIONS OF
CENTRAL MONTANA. AS LOW LEVEL UPSLOPE FLOW STRENGTHENS AND A BROAD
AREA OF UPWARD VERTICAL MOTION MOVES ACROSS THE REGION AM EXPECTING
WIDESPREAD SNOW TO DEVELOP ACROSS THE SOUTHERN HALF OF MY CWA
TONIGHT. THE UPPER TROUGH WILL CONTINUE TO STRENGTHEN...BECOMING A
CUTOFF LOW OVER THE GREAT BASIN BY FRIDAY MORNING. THIS FEATURE IS
EXPECTED TO REMAIN IN THIS GENERAL AREA WITH A GRADUAL DRIFT TO
THE NORTHEAST THROUGH SATURDAY AFTERNOON. ABUNDANT MOISTURE WILL
BE PUMPED INTO CENTRAL AND SOUTHWEST MONTANA WITH LIGHT SNOW
CONTINUING ACROSS THE SOUTHERN HALF OF MY CWA THROUGH THE WEEKEND.
HAVE DECIDED TO ISSUE A WINTER STORM WARNING FOR THE ENTIRE
SOUTHERN HALF OF MY FORECAST AREA BEGINNING TONIGHT AND CONTINUING
CLEAR THROUGH SUNDAY AFTERNOON. ALTHOUGH SNOW AMOUNTS ARE NOT
EXPECTED TO BE ESPECIALLY HEAVY IN ANY 12 OR 24 HOUR PERIOD...AND
THERE WILL INITIALLY BE SOME MELTING DUE TO WARM GROUND
TEMPERATURES...BY THE END OF THE WEEKEND AM EXPECTING 3 TO 6
INCHES SNOWFALL OVER THE PLAINS...WITH 15 TO 30 INCHES OVER THE
MOUNTAINS. I AM ALSO EXPECTING THAT THERE COULD BE SOME DAMAGE TO
TREES SINCE THERE ARE STILL LEAVES HAVE NOT FALLEN IN SOME
LOCATIONS...AND ROADWAYS COULD BECOME QUITE SLICK AS MELTING SNOW
FREEZES ONCE TEMPERATURES FALL. MPJ
FOR MONDAY THROUGH TUESDAY...EXPECT A NICE WARMING TREND OVER THE
REGION...AS A WEAK UPPER LEVEL RIDGE TRIES TO REBUILD OVER THE
REGION. TEMPERATURES WILL WARM UP NICELY IN THE CUT BANK AREA...AS A
BROWN GROUND AND BREEZY WEST WIND DEVELOPS. HOWEVER...IN AREAS THAT
RECEIVE A SNOW COVER OVER SOUTHWEST AND CENTRAL MONTANA...IT WILL
TAKE A FEW DAYS FOR THE SNOW TO MELT AND TEMPERATURES WILL BE SLOWER
TO WARM UP. ANY PRECIP WILL BE CONFINED MAINLY TO THE WESTERN
MOUNTAINS ON TUESDAY. BRUSDA
WEDNESDAY AND THURSDAY...LATEST MODELS INDICATE A HIGH PRESSURE
BUILDING OVER THE PACIFIC NORTHWEST DURING THIS PERIOD. WEAK
DISTURBANCES WILL FLOW THROUGH BUT MOISTURE APPEARS LIMITED AT THIS
POINT SO KEPT SLIGHT CHANCE POPS ALONG THE DIVIDE. TEMPERATURES ARE
EXPECTED TO BE NEAR SEASONAL AVERAGES. JNS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 26 37 23 34 / 60 30 50 40
CTB 24 37 21 34 / 20 30 30 30
HLN 30 39 25 34 / 60 60 50 50
BZN 29 38 26 36 / 90 100 80 70
WEY 22 33 19 30 / 60 80 70 80
DLN 25 33 20 30 / 80 70 60 50
HVR 24 44 25 39 / 20 20 30 30
LWT 26 36 22 30 / 90 70 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT SUNDAY
FOR MTZ008-012-014-015-050>055.
&&
$$
SHORT TERM...EMANUEL/MPJ
LONG TERM...BRUSDA/JNS
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KBYZ 100313
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
913 PM MDT THU OCT 9 2008
.SHORT TERM...VALID FOR FRI AND SAT...
NO MAJOR CHANGES TO THE GOING FORECAST. TWEAKED PRECIPITATION AND
SNOWFALL AMOUNTS SLIGHTLY IN A FEW LOCATIONS BASED ON CURRENT
TRENDS. STRONG ISENTROPIC FORCING OVER CENTRAL AND WESTERN ZONES
IS RESULTING IN LIGHT TO MODERATE SNOWFALL RATES THIS EVENING.
SOME HEAVIER BURSTS OF SNOW HAVE BEEN NOTED IN THE COOKE CITY AREA
EARLIER WITH A QUICK COUPLE OF INCHES. TEMPERATURES ARE HOVERING
IN THE LOW TO MID 30S IN THE WEST AND CENTRAL AND SOUTHEAST WHERE
STRONGEST FORCING IS LOCATED...WARMER TEMPERATURES NORTHEAST WHERE
FORCING AND DYNAMIC COOLING ARE NOT QUITE AS STRONG. WILL CONTINUE
TO SEE TEMPERATURES SLOWLY COOL INTO THE UPPER 20S AND LOWER 30S
OVERNIGHT...WITH MODELS AGREEING ON CONTINUED STRONG ISENTROPIC
LIFT ON THE 290-300K SURFACES KEEPING STEADY LIGHT TO MODERATE
PRECIPITATION GOING. OCCASIONAL PERIODS OF UPPER LEVEL DYNAMICS
WILL ENHANCE PRECIPITATION RATES RESULTING IN BRIEF HEAVY SNOWFALL
AT TIMES. ROAD SURFACE TEMPERATURES ARE SLOWLY FALLING INTO THE
30S ACROSS THE AREA WITH MID 30S IN THE BILLINGS AREA. SHOULD SEE
SNOW START TO STICK ON ROADWAYS AFTER MIDNIGHT FROM BILLINGS
WEST...AND AT ELEVATIONS ABOVE 4500 FEET IN THE EAST. BY MORNING
SNOW WILL LIKELY BE STICKING TO ROAD SURFACES ACROSS THE AREA.
EVEN SMALL ACCUMULATIONS OF HEAVY WET SNOW WILL CAUSE TREE AND
POWER LINE DAMAGE...AND SHOULD SEE SUFFICIENT ACCUMULATIONS BY LATE
TONIGHT TO START TO SEE THIS OCCUR. THIS IS COVERED WELL IN THE
CURRENT WARNING AND WILL ONLY UPDATE THE WARNING TO REFRESH
WORDING. CHAMBERS
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
THE WINTER STORMS IMPACT WILL CONTINUE INTO SUNDAY. GFS/ECMWF
CONSISTENT WITH UPPER LOW PROGRESSING FROM NORTHERN WYOMING INTO
EASTERN MONTANA ON SUNDAY. WRAP AROUND MOISTURE WILL REMAIN
ENTRENCHED ACROSS THE REGION. GIVEN THIS TRACK SOLUTION...THE
HEAVIEST SNOW WOULD LINGER FROM BILLINGS NORTHWESTWARD FOR YET
ANOTHER 3 OR 5 INCHES OF ADDITIONAL SNOWFALL INTO SUNDAY NIGHT. A
FEW SNOW SHOWERS COULD LINGER IN CYCLONIC FLOW AROUND THE SYSTEM
INTO MONDAY BUT NO ADDITIONAL ACCUMULATIONS BEFORE EVERYTHING
CLEARS OUT.
MOSTLY DRY PATTERN DEVELOPS FOR TUESDAY AND BEYOND AS FLOW BECOMES
MORE ZONAL AND DOWNSLOPE. HAVE LOWERED TEMPERATURES EARLY IN THE
WEEK IN ANTICIPATION OF A DEEPER SNOW COVER TO MELT OFF. FRIEDERS
&&
.AVIATION...
SNOW WILL CONTINUE THROUGHOUT THE NIGHT TONIGHT. LOCATIONS FROM
KMLS-KBHK STILL EXPERIENCING SOME LIGHT RAIN NOW BUT THIS IS
EXPECTED TO CHANGE OVER TO SNOW LATER THIS EVENING. THE SNOW WILL
BE HEAVY AT TIMES...MAINLY FROM A KMLS-KBIL-KLVM LINE AND AREAS
SOUTH. CONDITIONS WILL CONTINUE TO DETERIORATE THROUGHOUT THE
EVENING AND OVERNIGHT HOURS WITH LOWERING VISIBILITIES AND
CEILINGS. EXPECT IFR TO LIFR WITH SOME VLIFR CONDITIONS
THROUGHOUT THE NIGHT. THE MOUNTAINS WILL BE OBSCURED.
FOR KBIL...EXPECT VLIFR CONDITIONS TO BE PREDOMINANT THROUGH MUCH
OF THE NIGHT WITH A FEW BRIEF PERIODS OF IMPROVEMENT TO LIFR
EXPECTED. SIGNIFICANT IMPROVEMENT TO IFR LEVELS IS NOT LIKELY UNTIL
POSSIBLY MID MORNING FRIDAY WITH STRONG ISENTROPIC LIFT
CONTINUING...AND THOSE PERIODS WILL BE BRIEF. HOOLEY/CHAMBERS
&&
.PRELIMINARY POINT TEMP/POPS...
FRI SAT SUN MON TUE WED THU
-----------------------------------------------------------
BIL 027/034 026/033 026/034 023/043 028/053 032/053 033/054
++/S ++/S +8/S 31/B 10/B 11/B 11/B
LVM 022/033 019/032 019/036 022/046 027/053 032/053 033/054
++/S ++/S +8/S 31/N 10/B 11/B 21/B
HDN 028/037 026/034 026/038 022/046 027/054 031/054 032/055
++/S ++/S +8/S 31/B 10/B 11/B 11/B
MLS 031/039 026/037 026/038 024/046 029/055 032/055 033/056
++/S 89/S 97/S 31/B 11/B 11/B 21/U
4BQ 030/037 025/035 025/037 023/046 028/055 030/055 031/056
++/S ++/S +6/S 31/B 10/U 11/U 21/B
BHK 027/037 025/035 025/039 022/045 024/053 029/053 031/054
++/S 78/S 85/O 31/B 11/B 11/B 21/B
SHR 028/036 025/034 026/035 022/045 027/053 029/053 031/054
++/S ++/S +8/S 31/B 10/U 11/U 12/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 28>42-56>58-63>68.
WY...WINTER STORM WARNING IN EFFECT UNTIL 6 AM MDT MONDAY FOR
ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 100301
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
901 PM MDT THU OCT 9 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT...
SATELLITE CHANNELS SHOW ENHANCEMENT WITH 115KT JET STREAK MOVING
ENE ACROSS ND. MOISTURE/CLOUDS ARE ALSO TENDING TO INCREASE BEHIND
THIS FEATURE THOUGH...ACROSS WY AND E MT. MODELS SHOW ANOTHER
ASSOCIATED JET STREAK DEVELOPING LATER TONIGHT IN WY. THIS
ASSOCIATED WITH THE UPPER TROUGH OVER THE PACIFIC NW THAT IS
INTENSIFYING AS IT MOVES SE...FORECAST BY MODELS TO CLOSE OFF LATE
TONIGHT. THIS IS CAUSING UPPER FLOW TO TIGHTEN AND BACK OVER E MT.
EXPANDING REFLECTIVITY IN S PART OF OUR CWA ON 88D RADAR...BUT
RETURNS ARE WEAK AND TEMP/DEW POINT SPREADS 15-25F. MODELS
INDICATE AIRMASS TO MOISTEN UP ENOUGH AND UPPER LEVEL DYNAMICS
STRENGTHEN...TO BEGIN SOME SIGNIFICANT RAINFALL. THE DRY AIRMASS
AND RESULTING LOW WET BULB TEMPS MEAN THAT ONCE THE RAIN GETS
GOING WITH SOME INTENSITY IT SHOULD TURN TO SNOW LATE TONIGHT.
DRIER AIRMASS IN N HALF OF CWA...WITH A SURFACE HIGH CENTER IN S
AB. THIS WILL KEEP N HALF OF CWA GENERALLY DRY TONIGHT. MODELS
SEEM TO HAVE ONLY A FAIR HANDLE ON FEATURES FOR TONIGHT...BUT THE
ONGOING FORECAST IS REASONABLE...AND SO UPDATES IN AWAITING FOR
THE EXPECTED PRECIP SCENARIO TO GET GOING. SIMONSEN
PREVIOUS SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH
SATURDAY...A BUSY FEW DAYS...WEATHER WISE...IN STORE FOR NORTHEAST
MONTANA. AN UPPER TROUGH DIGGING INTO THE GREAT BASIN WILL EJECT
WARMER MORE MOIST AIR OVER A POLAR AIRMASS IN PLACE OVER EASTERN
MONTANA. THIS OVERRUNNING WILL DRIVE A MIX OF RAIN AND SNOW ACROSS
THE SOUTHERN ZONES...MAINLY SOUTH OF HIGHWAY 200. HAVE UPGRADED
THE EXISTING WATCH FOR THE SOUTHERN ZONES TO A WINTER STORM
WARNING. NORTHERLY WINDS OF 15 TO 25 MPH WILL ACCOMPANY THE
STORM...HOWEVER GIVEN THE HEAVY WET NATURE TO THE SNOWFALL DO NOT
EXPECT MUCH IN THE WAY OF BLOWING AND DRIFTING. THESE WINDS MAY
ALSO REQUIRE A LAKE WIND ADVISORY FOR FORT PECK LAKE FRIDAY
AFTERNOON. BY FRIDAY EVENING THE LIFT GENERATED BY THE OVERRUNNING
WILL TAPER OFF...SUBSEQUENTLY TAPERING OFF THE RAIN AND SNOW. THIS
LULL WILL LAST INTO SATURDAY MORNING...BEFORE A SECOND MORE
POTENT/WET SYSTEM MOVES IN FROM THE SOUTH. COORDINATED A WATCH
WITH THE EXTENDED FORECASTER THAT STARTS SATURDAY AFTERNOON FOR
AREAS SOUTH OF THE MISSOURI RIVER. SIGNIFICANT SNOW ACCUMULATION
CAN BE EXPECTED ACROSS THE WHOLE OF NORTHEAST MONTANA WITH THIS
SECOND STORM SYSTEM. GILCHRIST
.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
ONLY MINOR ADJUSTMENTS INTRODUCED TO THE GOING PACKAGE AS
CONFIDENCE REMAINS HIGH IN A MAJOR STORM SYSTEM THIS WEEKEND.
LATEST GFS ENSEMBLES MAINTAIN A TIGHT CLUSTER OF UPPER LOW TRACKS
THROUGH 00Z MONDAY WITH THE DETERMINISTIC RUN EXHIBITING ONLY
SMALL DEVIATIONS FROM PREVIOUS RUNS. ON THE OTHER HAND...THE 12Z
ECMWF HAS TRENDED SLOWER WITH THE LOW/S PROGRESSION BUT AT LEAST
STICKS TO A SIMILAR TRACK. GIVEN PRONOUNCED UPPER LEVEL DIVERGENCE
SATURDAY NIGHT INTO SUNDAY HELPING TO SUSTAIN A WARM TROWAL
SIGNATURE ALONG THE 295-305K ISENTROPIC SURFACE...PERIODS OF HEAVY
SNOW ARE CERTAINLY POSSIBLE AS THE 700MB LOW TRACKS NEAR THE I-94
CORRIDOR. DID RAMP UP SNOW AMOUNTS GIVEN THIS FORCING AND ALSO
ISSUED TWO WINTER STORM WATCHES TO BETTER ADDRESS THE ONSET OF
ACCUMULATING SNOW. MCZ
PREVIOUS LONG TERM DISCUSSION...
A WINTER-LIKE CYCLONIC STORM SYSTEM WILL BE WELL UNDERWAY AND
MOVING THROUGH EASTERN MONTANA WHEN THE EXTENDED PERIOD OPENS ITS
DOOR SATURDAY NIGHT. MODELS AND ENSEMBLES HAVE BECOME COMFORTABLE
WITH THIS WEEKEND STORM. THE USUAL EXPLODED ENSEMBLE SPAGHETTI
PLOTS HAVE ALL LINED UP CRISPLY AROUND THIS LOW THROUGH SUNDAY.
THE 00Z GFS HAS COME TO CLOSELY RESEMBLE THE 12Z ECMWF IN TIMING
AND LOCATION. DETAILS BEGIN TO FUZZ A LITTLE SUNDAY NIGHT AND
MONDAY AS THE MAIN ENERGY OF THE STORM LIFTS INTO CANADA AND THE
FRONT MOVES EAST. MODELS BEGIN TO DIFFER ON HOW LONG THE WRAP-
AROUND COMMA HEAD LINGERS OVER THE FORECAST AREA ON MONDAY. SINCE
THE SYSTEM HAS BEEN RATHER PROGRESSIVE IT WOULD MAKE SENSE THAT BY
MONDAY AFTERNOON THE STORM WILL HAVE EXITED EAST...REPLACED BY A
TEMPORARILY AMPLIFIED UPPER RIDGE FROM THE WEST. THE RIDGE WILL
BECOME FLATTENED TUESDAY BY A QUICK-MOVING SHORTWAVE TREKKING
ACROSS NORTHERN ALBERTA/SASKATCHEWAN. THE REMAINDER OF THE PERIOD
SHOULD CONTINUE MOSTLY DRY AND SEASONAL WITH NEAR ZONAL UPPER
FLOW.
THE MAIN QUESTION CONCERNING SATURDAY NIGHT AND SUNDAY WILL BE
THE AMOUNT OF SNOW THAT COULD FALL. THE LARGE UPPER CLOSED LOW
WILL BE CENTERED OVER SOUTHEASTERN IDAHO AND WESTERN WYOMING. THIS
WILL BE THE PERFECT SPOT TO DIRECT A VERY STRONG UPPER JET INTO
EASTERN MONTANA AND THE WESTERN DAKOTAS. IN ADDITION AN INVERTED
SURFACE TROUGH WILL BE SLIDING NORTH INTO THE SAME AREA. THE
RESULT WILL BE VERY STRONG OMEGA LIFT AND SUPPORT ALONG WITH VERY
IMPRESSIVE NEGATIVE Q-VECTOR DIVERGENCE NUMBERS. THE RESULTING QPF
FOCUS IN THE AFOREMENTIONED AREAS SATURDAY NIGHT IS A HALF INCH TO
INCH OF WATER...WITH ANOTHER HALF INCH ON SUNDAY. THE AMOUNT OF
SNOWFALL COULD DEPEND ON THE TEMPERATURES AND HOW THE
PRECIPITATION BEGINS ON SATURDAY DURING THE DAY. 850MB
TEMPERATURES SATURDAY WILL BEGIN AROUND -4C AND DROP TO -6C BY
SUNDAY MORNING...WHILE GUIDANCE SUGGESTS SURFACE TMIN IN THE MID
20S THEN RISING INTO THE MID 30S SUNDAY. WITH THE PROGRESSIVE
NATURE OF THIS STORM THE RESULTING TEMPERATURES COULD DEVIATE
QUITE A BIT FROM GUIDANCE. EXPECT THE MAJORITY OF PRECIPITATION
TO FALL AS SNOW BUT THE COLD BOUNDARY ONLY EXTENDS A SHORT WAY
BEYOND THE EASTERN BORDER SO THERE REMAINS UNCERTAINTY IN
PRECIPITATION TYPE. SCT
&&
.AVIATION...
VFR THIS EVENING WITH NORTHEAST WINDS REMAINING AROUND 10 KTS AT
ALL TERMINALS. MID LEVEL CLOUDS WILL CONTINUE TO INCREASE IN
COVERAGE TONIGHT AHEAD OF AN INTENSIFYING STORM SYSTEM IN WYOMING.
THIS STORM WILL NUDGE NORTH LATER TONIGHT MAINLY AFFECTING KGDV
WITH POSSIBLE MVFR CONDITIONS AND A MIX OF RAIN AND SNOW LATER
TONIGHT. MVFR CONDITIONS WITH A RAIN/SNOW MIX WILL SLOWLY SPREAD
NORTH ACROSS ALL TERMINALS FRIDAY. RAS/SCT
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND
SOUTHERN VALLEY-DANIELS-SHERIDAN-WESTERN ROOSEVELT-NORTHERN
PHILLIPS-SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT.
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT FRIDAY
FOR PETROLEUM-GARFIELD-DAWSON-PRAIRIE-WIBAUX.
WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
AFTERNOON FOR PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-
WIBAUX.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 100255
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
850 PM MDT THU OCT 9 2008
.DISCUSSION...
UPDATE FORTHCOMING. HAVE MADE RELATIVELY MINOR ADJUSTMENTS TO THE
POP GRIDS TONIGHT MAINLY TO BETTER ALIGN WITH NEIGHBORING OFFICES.
FIRST SIGNIFICANT WINTER STORM OF THE SEASON CONTINUES TO DEVELOP
OVER THE AREA. DEEP UPPER TROF SLOWLY MOVES OVER THE AREA FRIDAY.
OVERRUNNING PRECIPITATION...MAINLY SNOW...STILL LOOKING GOOD THROUGH
THE WEEKEND. EMANUEL
&&
.AVIATION...
UPDATED 0025Z.
AN UPPER LEVEL TROUGH WILL CONTINUE TO DEEPEN OVER THE PACIFIC
NORTHWEST AND INTO THE GREAT BASIN THROUGH 00Z SATURDAY. THE
EASTERLY FLOW ALOFT WILL BECOME INCREASINGLY MOIST DURING THE
PERIOD. HOWEVER...NORTH CENTRAL MONTANA (KCTB AND KHVR TERMINALS)
WILL REMAIN ON THE NORTHERN EDGE OF THE MOISTURE...WHERE VFR
CONDITIONS WITH AREAS OF MID LEVEL CLOUDINESS AND A FEW SHOWERS WILL
PERSIST. FARTHER SOUTH...ACROSS CENTRAL (KGTF AND KLWT) AND
SOUTHWEST (KHLN AND KBZN) MONTANA...WIDESPREAD CLOUDINESS AND
PRECIPITATION WILL KEEP CONDITIONS IN THE LOW VFR/HIGH MVFR RANGE
WITH MOUNTAIN OBSCURATION. HOWEVER...CONDITIONS OVERNIGHT MAY LOWER
TO IFR LEVELS AT TIMES DUE TO CLOUDS AND SNOW. SURFACE WINDS WILL
GENERALLY REMAIN NORTHEASTERLY AND BREEZY. COULSTON
&&
.PREV DISCUSSION...ISSUED 242 PM MDT THU OCT 9 2008
TONIGHT THROUGH SUNDAY...FORECAST AREA IS BENEATH THE INFLUENCE
OF A DEVELOPING UPPER LEVEL TROUGH. FORECAST CONTINUES TO LOOK
FAVORABLE FOR THE DEVELOPMENT OF A SIGNIFICANT EARLY SEASON WINTER
STORM. SHOWERS ARE ALREADY DEVELOPING ACROSS SOUTHERN PORTIONS OF
CENTRAL MONTANA. AS LOW LEVEL UPSLOPE FLOW STRENGTHENS AND A BROAD
AREA OF UPWARD VERTICAL MOTION MOVES ACROSS THE REGION AM EXPECTING
WIDESPREAD SNOW TO DEVELOP ACROSS THE SOUTHERN HALF OF MY CWA
TONIGHT. THE UPPER TROUGH WILL CONTINUE TO STRENGTHEN...BECOMING A
CUTOFF LOW OVER THE GREAT BASIN BY FRIDAY MORNING. THIS FEATURE IS
EXPECTED TO REMAIN IN THIS GENERAL AREA WITH A GRADUAL DRIFT TO
THE NORTHEAST THROUGH SATURDAY AFTERNOON. ABUNDANT MOISTURE WILL
BE PUMPED INTO CENTRAL AND SOUTHWEST MONTANA WITH LIGHT SNOW
CONTINUING ACROSS THE SOUTHERN HALF OF MY CWA THROUGH THE WEEKEND.
HAVE DECIDED TO ISSUE A WINTER STORM WARNING FOR THE ENTIRE
SOUTHERN HALF OF MY FORECAST AREA BEGINNING TONIGHT AND CONTINUING
CLEAR THROUGH SUNDAY AFTERNOON. ALTHOUGH SNOW AMOUNTS ARE NOT
EXPECTED TO BE ESPECIALLY HEAVY IN ANY 12 OR 24 HOUR PERIOD...AND
THERE WILL INITIALLY BE SOME MELTING DUE TO WARM GROUND
TEMPERATURES...BY THE END OF THE WEEKEND AM EXPECTING 3 TO 6
INCHES SNOWFALL OVER THE PLAINS...WITH 15 TO 30 INCHES OVER THE
MOUNTAINS. I AM ALSO EXPECTING THAT THERE COULD BE SOME DAMAGE TO
TREES SINCE THERE ARE STILL LEAVES HAVE NOT FALLEN IN SOME
LOCATIONS...AND ROADWAYS COULD BECOME QUITE SLICK AS MELTING SNOW
FREEZES ONCE TEMPERATURES FALL. MPJ
FOR MONDAY THROUGH TUESDAY...EXPECT A NICE WARMING TREND OVER THE
REGION...AS A WEAK UPPER LEVEL RIDGE TRIES TO REBUILD OVER THE
REGION. TEMPERATURES WILL WARM UP NICELY IN THE CUT BANK AREA...AS A
BROWN GROUND AND BREEZY WEST WIND DEVELOPS. HOWEVER...IN AREAS THAT
RECEIVE A SNOW COVER OVER SOUTHWEST AND CENTRAL MONTANA...IT WILL
TAKE A FEW DAYS FOR THE SNOW TO MELT AND TEMPERATURES WILL BE SLOWER
TO WARM UP. ANY PRECIP WILL BE CONFINED MAINLY TO THE WESTERN
MOUNTAINS ON TUESDAY. BRUSDA
WEDNESDAY AND THURSDAY...LATEST MODELS INDICATE A HIGH PRESSURE
BUILDING OVER THE PACIFIC NORTHWEST DURING THIS PERIOD. WEAK
DISTURBANCES WILL FLOW THROUGH BUT MOISTURE APPEARS LIMITED AT THIS
POINT SO KEPT SLIGHT CHANCE POPS ALONG THE DIVIDE. TEMPERATURES ARE
EXPECTED TO BE NEAR SEASONAL AVERAGES. JNS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 26 37 23 34 / 60 30 50 40
CTB 24 37 21 34 / 20 30 30 30
HLN 30 39 25 34 / 60 60 50 50
BZN 29 38 26 36 / 90 100 80 70
WEY 22 33 19 30 / 60 80 70 80
DLN 25 33 20 30 / 80 70 60 50
HVR 24 44 25 39 / 20 20 30 30
LWT 26 36 22 30 / 90 70 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT SUNDAY
FOR MTZ008-012-014-015-050>055.
&&
$$
SHORT TERM...EMANUEL/MPJ
LONG TERM...BRUSDA/JNS
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KMSO 100152
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
752 PM MDT THU OCT 9 2008
.UPDATE...INCREASED THE POTENTIAL FOR PRECIPITATION THIS EVENING
IN THE VALLEYS OF WESTERN MONTANA. ALSO INCREASED WINDS THROUGH
TONIGHT IN THE HIGHER ELEVATIONS.
&&
.DISCUSSION...A BROAD AREA OF LIGHT RAIN AND SNOW SHOWERS
CONTINUES OVER WESTERN MONTANA AND CENTRAL IDAHO THIS EVENING.
SNOW LEVELS HAVE DIPPED BETWEEN 4500 AND 5000 FEET ALONG AND JUST
WEST OF THE CONTINENTAL DIVIDE. MANY MOUNTAIN PASSES HAVE SEEN AT
LEAST SOME MINOR SNOW ACCUMULATIONS. SOME RAIN AND SNOW HAVE BEEN
REPORTED IN THE VALLEYS ACROSS WESTERN MONTANA THIS EVENING SO
DECIDED TO INCREASE THE POTENTIAL FOR MEASURABLE
PRECIPITATION...THOUGH ANY SNOW ACCUMULATIONS WILL STILL BE MINOR.
&&
.AVIATION...A COLD AND WINTRY WEATHER SYSTEM WILL IMPACT THE
NORTHERN ROCKIES BEGINNING THIS EVENING AND CONTINUING THROUGH THE
WEEKEND BEFORE EXITING THE AREA. EASTERLY WINDS WILL INCREASE AND
BECOME GUSTY THIS EVENING AS THE SURFACE PRESSURE GRADIENT
TIGHTENS. WINDS ARE EXPECTED TO REMAIN STRONG THROUGH FRIDAY NIGHT.
SNOW AND BLOWING SNOW WILL IMPACT THE NORTHERN ROCKIES WITH THIS
SYSTEM WITH HEAVIER SNOWFALL EXPECTED NEAR TERMINALS KSMN AND
KBTM. IFR CEILINGS ARE NOT OUT OF THE QUESTION NEAR THESE
TERMINALS AND THEIR VICINITIES UNDER HEAVIER BANDS OF
PRECIPITATION. VISIBILITIES WILL BE REDUCED AT TIMES WITH MOUNTAIN
AND PASS OBSCURATIONS LIKELY.
&&
.PREV DISCUSSION... /ISSUED 250 PM MDT THU OCT 9 2008/
..FIRST MAJOR WINTER STORM OF THE FALL SEASON TO AFFECT SOUTHWEST
MONTANA AND LEMHI COUNTY IDAHO...
DISCUSSION...A HIGHLY DYNAMIC WINTER WEATHER SYSTEM WILL BEGIN TO
AFFECT THE NORTHERN ROCKIES STARTING TONIGHT AND WILL CONTINUE
THROUGH THE DURATION OF THE WEEKEND. LOCATIONS IN HIGHER
ELEVATIONS ABOVE 5500 FEET WILL BE THE FIRST TO SEE SNOW SHOWERS
DEVELOPING THIS EVENING WITH LIGHT ACCUMULATIONS POSSIBLE. AREAS
TO BE MOSTLY IMPACTED BY THESE ACCUMULATIONS WILL BE ALONG THE
CONTINENTAL DIVIDE...LEMHI COUNTY AND LOST TRAIL PASS. NORTHWEST MT
VALLEYS WILL NOT BE IMPACTED BY SNOW WITH THIS EVENT...BUT WILL
EXPERIENCE GUSTY NORTHEAST WINDS.
SNOW OVER SOUTHWEST MT AND LEMHI COUNTY WILL CONTINUE STEADILY
THROUGH THE DAY FRIDAY AND INTO SATURDAY WITH SNOW LEVELS LOWERING
TO THE VALLEY FLOORS AND MAY EXPERIENCE LIGHT SNOW ACCUMULATIONS. A
TIGHTENING NORTHEAST TO SOUTHEAST PRESSURE GRADIENT WILL ALLOW
GUSTY NORTHEAST WINDS TO DEVELOP FRIDAY THROUGH SATURDAY...WITH
AREAS OF BLOWING SNOW. IT SHOULD BE NOTED THAT WITH THESE TYPE OF
GUSTY WINDS...OVERNIGHT TEMPERATURES WILL FEEL QUITE BRISK AS THE
WINDS HELP TO LOWER TEMPERATURES INTO THE TEENS. DUE TO THE EARLY
ONSET OF SNOW FOR THIS SEASON...DECIDUOUS TREES RUN THE RISK OF
BROKEN BRANCHES DUE TO ACCUMULATING SNOW. WINTER WEATHER
ADVISORIES HAVE BEEN UPGRADED TO WINTER STORM WARNINGS TO ACCOUNT
FOR THE LONG DURATION OF ACCUMULATING SNOW AND THE POSSIBILITY OF
DAMAGE TO TREES.
THE DEEP LOW PRESSURE SYSTEM WILL DIG AS FAR SOUTH AS UTAH BY
SATURDAY AFTERNOON WITH MOISTURE WRAPPING AROUND IT...CONTINUING
SNOWS OVER SOUTHWEST MT AND LEMHI COUNTY INTO EARLY SUNDAY. BY SUNDAY
AFTERNOON...THE LOW TRACKS INTO EASTERN MT WITH SNOW TAPERING
OFF. ANOTHER VERY COLD NIGHT IS EXPECTED SUNDAY NIGHT...AS CLOUDS
BEGIN TO CLEAR OUT OF THE AREA.
MONDAY THROUGH THURSDAY...A BRIEF DRY PERIOD WILL TAKE HOLD ON MONDAY
AS THE OVERALL WEATHER PATTERN TRANSITIONS FROM THE STRONG UPPER
LEVEL LOW FROM THE PAST WEEKEND TO MORE OF A WESTERLY FLOW FOR THE
REMAINDER OF THE WEEK. THIS TYPE OF FLOW PATTERN TYPICALLY
INDICATES A SHOWERY PRECIPITATION REGIME THAT SHOULD BE CONFINED
MAINLY TO HIGHER TERRAIN.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING FROM 3 AM FRIDAY TO 6 PM MDT SATURDAY FOR
BUTTE/BLACKFOOT REGION.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM MDT
FRIDAY FOR BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT SATURDAY
FOR EASTERN LEMHI COUNTY.
&&
$$
UPDATE...LOEFFELBEIN
PREVIOUS DISCUSSION...ALLEGRETTO/FELSCH
AVIATION...LOEFFELBEIN
000
FXUS65 KTFX 100027
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
625 PM MDT THU OCT 9 2008
...UPDATE TO AVIATION...
.DISCUSSION...
TONIGHT THROUGH SUNDAY...FORECAST AREA IS BENEATH THE INFLUENCE
OF A DEVELOPING UPPER LEVEL TROUGH. FORECAST CONTINUES TO LOOK
FAVORABLE FOR THE DEVELOPMENT OF A SIGNIFICANT EARLY SEASON WINTER
STORM. SHOWERS ARE ALREADY DEVELOPING ACROSS SOUTHERN PORTIONS OF
CENTRAL MONTANA. AS LOW LEVEL UPSLOPE FLOW STRENGTHENS AND A BROAD
AREA OF UPWARD VERTICAL MOTION MOVES ACROSS THE REGION AM EXPECTING
WIDESPREAD SNOW TO DEVELOP ACROSS THE SOUTHERN HALF OF MY CWA
TONIGHT. THE UPPER TROUGH WILL CONTINUE TO STRENGTHEN...BECOMING A
CUTOFF LOW OVER THE GREAT BASIN BY FRIDAY MORNING. THIS FEATURE IS
EXPECTED TO REMAIN IN THIS GENERAL AREA WITH A GRADUAL DRIFT TO
THE NORTHEAST THROUGH SATURDAY AFTERNOON. ABUNDANT MOISTURE WILL
BE PUMPED INTO CENTRAL AND SOUTHWEST MONTANA WITH LIGHT SNOW
CONTINUING ACROSS THE SOUTHERN HALF OF MY CWA THROUGH THE WEEKEND.
HAVE DECIDED TO ISSUE A WINTER STORM WARNING FOR THE ENTIRE
SOUTHERN HALF OF MY FORECAST AREA BEGINNING TONIGHT AND CONTINUING
CLEAR THROUGH SUNDAY AFTERNOON. ALTHOUGH SNOW AMOUNTS ARE NOT
EXPECTED TO BE ESPECIALLY HEAVY IN ANY 12 OR 24 HOUR PERIOD...AND
THERE WILL INITIALLY BE SOME MELTING DUE TO WARM GROUND
TEMPERATURES...BY THE END OF THE WEEKEND AM EXPECTING 3 TO 6
INCHES SNOWFALL OVER THE PLAINS...WITH 15 TO 30 INCHES OVER THE
MOUNTAINS. I AM ALSO EXPECTING THAT THERE COULD BE SOME DAMAGE TO
TREES SINCE THERE ARE STILL LEAVES HAVE NOT FALLEN IN SOME
LOCATIONS...AND ROADWAYS COULD BECOME QUITE SLICK AS MELTING SNOW
FREEZES ONCE TEMPERATURES FALL. MPJ
FOR MONDAY THROUGH TUESDAY...EXPECT A NICE WARMING TREND OVER THE
REGION...AS A WEAK UPPER LEVEL RIDGE TRIES TO REBUILD OVER THE
REGION. TEMPERATURES WILL WARM UP NICELY IN THE CUT BANK AREA...AS A
BROWN GROUND AND BREEZY WEST WIND DEVELOPS. HOWEVER...IN AREAS THAT
RECEIVE A SNOW COVER OVER SOUTHWEST AND CENTRAL MONTANA...IT WILL
TAKE A FEW DAYS FOR THE SNOW TO MELT AND TEMPERATURES WILL BE SLOWER
TO WARM UP. ANY PRECIP WILL BE CONFINED MAINLY TO THE WESTERN
MOUNTAINS ON TUESDAY. BRUSDA
WEDNESDAY AND THURSDAY...LATEST MODELS INDICATE A HIGH PRESSURE
BUILDING OVER THE PACIFIC NORTHWEST DURING THIS PERIOD. WEAK
DISTURBANCES WILL FLOW THROUGH BUT MOISTURE APPEARS LIMITED AT THIS
POINT SO KEPT SLIGHT CHANCE POPS ALONG THE DIVIDE. TEMPERATURES ARE
EXPECTED TO BE NEAR SEASONAL AVERAGES. JNS
&&
.AVIATION...
UPDATED 0025Z.
AN UPPER LEVEL TROUGH WILL CONTINUE TO DEEPEN OVER THE PACIFIC
NORTHWEST AND INTO THE GREAT BASIN THROUGH 00Z SATURDAY. THE
EASTERLY FLOW ALOFT WILL BECOME INCREASINGLY MOIST DURING THE
PERIOD. HOWEVER...NORTH CENTRAL MONTANA (KCTB AND KHVR TERMINALS)
WILL REMAIN ON THE NORTHERN EDGE OF THE MOISTURE...WHERE VFR
CONDITIONS WITH AREAS OF MID LEVEL CLOUDINESS AND A FEW SHOWERS WILL
PERSIST. FARTHER SOUTH...ACROSS CENTRAL (KGTF AND KLWT) AND
SOUTHWEST (KHLN AND KBZN) MONTANA...WIDESPREAD CLOUDINESS AND
PRECIPITATION WILL KEEP CONDITIONS IN THE LOW VFR/HIGH MVFR RANGE
WITH MOUNTAIN OBSCURATION. HOWEVER...CONDITIONS OVERNIGHT MAY LOWER
TO IFR LEVELS AT TIMES DUE TO CLOUDS AND SNOW. SURFACE WINDS WILL
GENERALLY REMAIN NORTHEASTERLY AND BREEZY. COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 26 37 23 34 / 60 30 50 40
CTB 24 37 21 34 / 20 30 30 30
HLN 30 39 25 34 / 60 60 50 50
BZN 29 38 26 36 / 90 100 80 70
WEY 22 33 19 30 / 60 80 70 80
DLN 25 33 20 30 / 80 70 60 50
HVR 24 44 25 39 / 20 20 30 30
LWT 26 36 22 30 / 90 70 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT SUNDAY
FOR MTZ008-012-014-015-050>055.
&&
$$
SHORT TERM...MPJ
LONG TERM...BRUSDA/JNS
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KBYZ 092127
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
327 PM MDT THU OCT 9 2008
...MAJOR EARLY SEASON WINTER STORM WILL IMPACT THE AREA THROUGH THE
WEEKEND...
.SHORT TERM...VALID FOR FRI AND SAT...
CONFIDENCE CONTINUED TO INCREASE FOR MAJOR EARLY WINTER STORM TO
AFFECT THE REGION BEGINNING TONIGHT. WATER VAPOR IMAGERY SHOWED
UPPER TROUGH DIGGING INTO THE PACIFIC NW THIS AFTERNOON. THE
ECMWF/GFS/WRF WERE HANDLING THE SYSTEM WELL AND WERE SIMILAR WITH
THE EVOLUTION AND TRACK OF THE SYSTEM INTO SAT. MODELS HAVE ALSO
BEEN SHOWING GOOD RUN-TO-RUN CONTINUITY. HOWEVER...THE MODELS
DIVERGED A BIT WITH THEIR SOLUTIONS AFTER SAT.
BAROCLINIC LEAF EVIDENT ON SATELLITE AND RADAR IMAGERY THIS
AFTERNOON REFLECTED THE FRONTOGENESIS OCCURRING ALOFT WITH THE
DEVELOPING SYSTEM. SOME OF THE MOISTURE HAD MOVED N INTO THE
FORECAST AREA AND PRODUCED A FEW RAIN AND SNOW SHOWERS THIS
AFTERNOON. THE UPPER TROUGH WAS FORECAST TO CUT OFF INTO AN UPPER
LOW AS IT DIGS S INTO ID/N NV TONIGHT...AND A BAROCLINIC ZONE WILL
SET UP TO THE SE OF THE AREA. 700 MB WARM ADVECTION WILL HELP TO
QUICKLY SATURATE THE LOWERS LEVELS ACROSS THE AREA THIS EVENING AS
TEMPERATURES AT 850 MB FALL TO BETWEEN 0 AND -2 DEGS C. 700 MB FLOW
WILL BECOME E OVERNIGHT. THE SYSTEM WAS TAPPING PACIFIC MOISTURE
THIS AFTERNOON AND WILL HAVE PLENTY OF MOISTURE FOR PRECIPITATION
TONIGHT. ABOVE FACTORS SUPPORTED CATEGORICAL POPS ACROSS THE AREA.
WILL HAVE A RAIN/SNOW MIX EARLY THIS EVENING CHANGING TO ALL SNOW BY
LATE EVENING. FAVORABLE DENDRITIC GROWTH ZONE WILL BE HIGH IN THE
ATMOSPHERE TONIGHT SO SNOWFALL ACCUMULATIONS WILL BE BETWEEN 1 AND 4
INCHES WITH HIGHEST AMOUNTS IN THE FOOTHILLS AND MOUNTAINS.
THE UPPER LOW WILL ELONGATE OVER NV ON FRI AND SEND PIECES OF
VORTICITY NE THROUGH THE AREA. 850 MB TEMPERATURES WILL GENERALLY BE
BELOW ZERO THROUGH THE DAY. EAST TO NE FLOW WILL CONTINUE AT LOWER
TO MID LEVELS FAVORABLE FOR UPSLOPE AS 700 MB LOW REMAINS OVER ID.
THE MID LEVELS WILL COOL DOWN OVER THE WESTERN AND CENTRAL ZONES
WHICH WILL SUPPORT BETTER DENDRITIC GROWTH. TEMPERATURES SHOULD NOT
CLIMB OUT OF THE 30S ON FRI. CONTINUED CATEGORICAL POPS ACROSS THE
AREA WITH SEVERAL INCHES OF SNOW ACCUMULATION. AMOUNTS WILL AGAIN BE
HIGHER OVER THE FOOTHILLS AND MOUNTAINS.
FOR FRI NIGHT AND SAT...THE UPPER LOW WAS FORECAST TO DEEPEN OVER NV
AND SHIFT OVER TO N UT WHILE SENDING ENERGY NE THROUGH THE AREA.
UPPER DIFLUENCE WILL ALSO MOVE OVER THE REGION. IN ADDITION THE
SYSTEM WILL BEGIN TO TAP MOISTURE FROM THE TROPICAL SYSTEM NEAR THE
BAJA. THE COLDER AIR AT 700 MB WILL INTERSECT THE LIFT OVER THE
SOUTHERN PART OF THE AREA ALLOWING FOR GREATER SNOW ACCUMULATIONS.
OTHERWISE...SEVERAL INCHES OF SNOW WILL BE POSSIBLE. DID NOT MAKE
MANY CHANGES TO POPS.
ON SAT NIGHT...GFS BROUGHT SOME ENERGY OUT OF THE MAIN UPPER LOW
INTO SE MT AS THE MAIN LOW BEGINS WOBBLING NE. DYNAMICS AHEAD OF THE
LOW WILL INCREASE OVER THE AREA CONTINUING THE ACCUMULATING SNOW. IF
THE GFS PANS OUT...THE E COULD SEE SIGNIFICANT SNOW ACCUMULATION.
HAVE TRENDED HIGHER WITH SNOW ACCUMULATIONS OVER THE E DUE TO
INCREASED DYNAMICS AND FRONTAL BOUNDARY WRAPPING W INTO THE AREA.
HAVE GONE WITH A WINTER STORM WARNING FOR ENTIRE AREA BEGINNING AT
03Z TONIGHT TO COVER THE IMPACTS OF THE SYSTEM INCLUDING POSSIBLE
SIGNIFICANT SNOW ACCUMULATION SAT NIGHT...HEAVY WET SNOWFALL CAUSING
POWER OUTAGES AND EFFECTS ON TRAVEL. ARTHUR
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
THE WINTER STORMS IMPACT WILL CONTINUE INTO SUNDAY. GFS/ECMWF
CONSISTENT WITH UPPER LOW PROGRESSING FROM NORTHERN WYOMING INTO
EASTERN MONTANA ON SUNDAY. WRAP AROUND MOISTURE WILL REMAIN
ENTRENCHED ACROSS THE REGION. GIVEN THIS TRACK SOLUTION...THE
HEAVIEST SNOW WOULD LINGER FROM BILLINGS NORTHWESTWARD FOR YET
ANOTHER 3 OR 5 INCHES OF ADDITIONAL SNOWFALL INTO SUNDAY NIGHT. A
FEW SNOW SHOWERS COULD LINGER IN CYCLONIC FLOW AROUND THE SYSTEM
INTO MONDAY BUT NO ADDITIONAL ACCUMULATIONS BEFORE EVERYTHING
CLEARS OUT.
MOSTLY DRY PATTERN DEVELOPS FOR TUESDAY AND BEYOND AS FLOW BECOMES
MORE ZONAL AND DOWNSLOPE. HAVE LOWERED TEMPERATURES EARLY IN THE
WEEK IN ANTICIPATION OF A DEEPER SNOW COVER TO MELT OFF. FRIEDERS
&&
.AVIATION...
CONDITIONS WILL CONTINUE TO DETERIORATE THROUGH THIS FORECAST
PERIOD AS THE STORM SYSTEM CONTINUES TO DEVELOP. A RAIN/SNOW MIX
WILL START EARLY THIS EVENING AND MOST AREAS SHOULD TRANSITION TO
ALL SNOW BY MIDNIGHT WITH RAPIDLY LOWERING CEILINGS. THESE IMPACTS
TO CONTINUE WITH MOSTLY IFR TO LIFR CONDITIONS THROUGH FRIDAY.
FRIEDERS
&&
.PRELIMINARY POINT TEMP/POPS...
FRI SAT SUN MON TUE WED THU
-----------------------------------------------------------
BIL 027/034 026/033 026/034 023/043 028/053 032/053 033/054
++/S ++/S +8/S 31/B 10/B 11/B 11/B
LVM 022/033 019/032 019/036 022/046 027/053 032/053 033/054
++/S ++/S +8/S 31/N 10/B 11/B 21/B
HDN 028/037 026/034 026/038 022/046 027/054 031/054 032/055
++/S ++/S +8/S 31/B 10/B 11/B 11/B
MLS 031/039 026/037 026/038 024/046 029/055 032/055 033/056
++/O 89/S 97/S 31/B 11/B 11/B 21/U
4BQ 030/037 025/035 025/037 023/046 028/055 030/055 031/056
++/S ++/S +6/S 31/B 10/U 11/U 21/B
BHK 027/037 025/035 025/039 022/045 024/053 029/053 031/054
++/S 78/S 85/O 31/B 11/B 11/B 21/B
SHR 028/036 025/034 026/035 022/045 027/053 029/053 031/054
++/S ++/S +8/S 31/B 10/U 11/U 12/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT FROM 9 PM THIS EVENING TO 6 AM
MDT MONDAY FOR ZONES 28>42-56>58-63>68.
WY...WINTER STORM WARNING IN EFFECT FROM 9 PM THIS EVENING TO 6 AM
MDT MONDAY FOR ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 092103
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
303 PM MDT THU OCT 9 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...
A BUSY FEW DAYS...WEATHER WISE...IN STORE FOR NORTHEAST MONTANA. AN
UPPER TROUGH DIGGING INTO THE GREAT BASIN WILL EJECT WARMER MORE
MOIST AIR OVER A POLAR AIRMASS IN PLACE OVER EASTERN MONTANA. THIS
OVERRUNNING WILL DRIVE A MIX OF RAIN AND SNOW ACROSS THE SOUTHERN
ZONES...MAINLY SOUTH OF HIGHWAY 200. HAVE UPGRADED THE EXISTING
WATCH FOR THE SOUTHERN ZONES TO A WINTER STORM WARNING. NORTHERLY
WINDS OF 15 TO 25 MPH WILL ACCOMPANY THE STORM...HOWEVER GIVEN THE
HEAVY WET NATURE TO THE SNOWFALL DO NOT EXPECT MUCH IN THE WAY OF
BLOWING AND DRIFTING. THESE WINDS MAY ALSO REQUIRE A LAKE WIND
ADVISORY FOR FORT PECK LAKE FRIDAY AFTERNOON. BY FRIDAY EVENING
THE LIFT GENERATED BY THE OVERRUNNING WILL TAPER
OFF...SUBSEQUENTLY TAPERING OFF THE RAIN AND SNOW. THIS LULL WILL
LAST INTO SATURDAY MORNING...BEFORE A SECOND MORE POTENT/WET
SYSTEM MOVES IN FROM THE SOUTH. COORDINATED A WATCH WITH THE
EXTENDED FORECASTER THAT STARTS SATURDAY AFTERNOON FOR AREAS SOUTH
OF THE MISSOURI RIVER. SIGNIFICANT SNOW ACCUMULATION CAN BE
EXPECTED ACROSS THE WHOLE OF NORTHEAST MONTANA WITH THIS SECOND
STORM SYSTEM. GILCHRIST
.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
ONLY MINOR ADJUSTMENTS INTRODUCED TO THE GOING PACKAGE AS
CONFIDENCE REMAINS HIGH IN A MAJOR STORM SYSTEM THIS WEEKEND.
LATEST GFS ENSEMBLES MAINTAIN A TIGHT CLUSTER OF UPPER LOW TRACKS
THROUGH 00Z MONDAY WITH THE DETERMINISTIC RUN EXHIBITING ONLY
SMALL DEVIATIONS FROM PREVIOUS RUNS. ON THE OTHER HAND...THE 12Z
ECMWF HAS TRENDED SLOWER WITH THE LOW/S PROGRESSION BUT AT LEAST
STICKS TO A SIMILAR TRACK. GIVEN PRONOUNCED UPPER LEVEL DIVERGENCE
SATURDAY NIGHT INTO SUNDAY HELPING TO SUSTAIN A WARM TROWAL
SIGNATURE ALONG THE 295-305K ISENTROPIC SURFACE...PERIODS OF HEAVY
SNOW ARE CERTAINLY POSSIBLE AS THE 700MB LOW TRACKS NEAR THE I-94
CORRIDOR. DID RAMP UP SNOW AMOUNTS GIVEN THIS FORCING AND ALSO
ISSUED TWO WINTER STORM WATCHES TO BETTER ADDRESS THE ONSET OF
ACCUMULATING SNOW. MCZ
PREVIOUS LONG TERM DISCUSSION...
A WINTER-LIKE CYCLONIC STORM SYSTEM WILL BE WELL UNDERWAY AND
MOVING THROUGH EASTERN MONTANA WHEN THE EXTENDED PERIOD OPENS ITS
DOOR SATURDAY NIGHT. MODELS AND ENSEMBLES HAVE BECOME COMFORTABLE
WITH THIS WEEKEND STORM. THE USUAL EXPLODED ENSEMBLE SPAGHETTI
PLOTS HAVE ALL LINED UP CRISPLY AROUND THIS LOW THROUGH SUNDAY.
THE 00Z GFS HAS COME TO CLOSELY RESEMBLE THE 12Z ECMWF IN TIMING
AND LOCATION. DETAILS BEGIN TO FUZZ A LITTLE SUNDAY NIGHT AND
MONDAY AS THE MAIN ENERGY OF THE STORM LIFTS INTO CANADA AND THE
FRONT MOVES EAST. MODELS BEGIN TO DIFFER ON HOW LONG THE WRAP-
AROUND COMMA HEAD LINGERS OVER THE FORECAST AREA ON MONDAY. SINCE
THE SYSTEM HAS BEEN RATHER PROGRESSIVE IT WOULD MAKE SENSE THAT BY
MONDAY AFTERNOON THE STORM WILL HAVE EXITED EAST...REPLACED BY A
TEMPORARILY AMPLIFIED UPPER RIDGE FROM THE WEST. THE RIDGE WILL
BECOME FLATTENED TUESDAY BY A QUICK-MOVING SHORTWAVE TREKKING
ACROSS NORTHERN ALBERTA/SASKATCHEWAN. THE REMAINDER OF THE PERIOD
SHOULD CONTINUE MOSTLY DRY AND SEASONAL WITH NEAR ZONAL UPPER
FLOW.
THE MAIN QUESTION CONCERNING SATURDAY NIGHT AND SUNDAY WILL BE
THE AMOUNT OF SNOW THAT COULD FALL. THE LARGE UPPER CLOSED LOW
WILL BE CENTERED OVER SOUTHEASTERN IDAHO AND WESTERN WYOMING. THIS
WILL BE THE PERFECT SPOT TO DIRECT A VERY STRONG UPPER JET INTO
EASTERN MONTANA AND THE WESTERN DAKOTAS. IN ADDITION AN INVERTED
SURFACE TROUGH WILL BE SLIDING NORTH INTO THE SAME AREA. THE
RESULT WILL BE VERY STRONG OMEGA LIFT AND SUPPORT ALONG WITH VERY
IMPRESSIVE NEGATIVE Q-VECTOR DIVERGENCE NUMBERS. THE RESULTING QPF
FOCUS IN THE AFOREMENTIONED AREAS SATURDAY NIGHT IS A HALF INCH TO
INCH OF WATER...WITH ANOTHER HALF INCH ON SUNDAY. THE AMOUNT OF
SNOWFALL COULD DEPEND ON THE TEMPERATURES AND HOW THE
PRECIPITATION BEGINS ON SATURDAY DURING THE DAY. 850MB
TEMPERATURES SATURDAY WILL BEGIN AROUND -4C AND DROP TO -6C BY
SUNDAY MORNING...WHILE GUIDANCE SUGGESTS SURFACE TMIN IN THE MID
20S THEN RISING INTO THE MID 30S SUNDAY. WITH THE PROGRESSIVE
NATURE OF THIS STORM THE RESULTING TEMPERATURES COULD DEVIATE
QUITE A BIT FROM GUIDANCE. EXPECT THE MAJORITY OF PRECIPITATION
TO FALL AS SNOW BUT THE COLD BOUNDARY ONLY EXTENDS A SHORT WAY
BEYOND THE EASTERN BORDER SO THERE REMAINS UNCERTAINTY IN
PRECIPITATION TYPE. SCT
&&
.AVIATION...
VFR THRU THIS EVENING WITH NORTHEAST WINDS REMAINING AROUND 10
KTS AT ALL TERMINALS. MID LEVEL CLOUDS WILL INCREASE IN COVERAGE
THIS EVENING AHEAD OF AN INTENSIFYING STORM SYSTEM IN WYOMING.
THIS STORM WILL NUDGE NORTH TONIGHT MAINLY AFFECTING KGDV WITH
POSSIBLE MVFR CONDITIONS AND A MIX OF RAIN AND SNOW AFTER 09Z.
MVFR CONDITIONS WITH A RAIN/SNOW MIX WILL SPREAD FROM SOUTH TO
NORTH ACROSS ALL TERMINALS BY MID MORNING. RAS
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND
SOUTHERN VALLEY-DANIELS-SHERIDAN-WESTERN ROOSEVELT-NORTHERN
PHILLIPS-SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT.
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT FRIDAY
FOR PETROLEUM-GARFIELD-DAWSON-PRAIRIE-WIBAUX.
WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
AFTERNOON FOR PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-
WIBAUX.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KMSO 092050
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
250 PM MDT THU OCT 9 2008
...FIRST MAJOR WINTER STORM OF THE FALL SEASON TO AFFECT SOUTHWEST
MONTANA AND LEMHI COUNTY IDAHO...
.DISCUSSION...A HIGHLY DYNAMIC WINTER WEATHER SYSTEM WILL BEGIN TO
AFFECT THE NORTHERN ROCKIES STARTING TONIGHT AND WILL CONTINUE
THROUGH THE DURATION OF THE WEEKEND. LOCATIONS IN HIGHER
ELEVATIONS ABOVE 5500 FEET WILL BE THE FIRST TO SEE SNOW SHOWERS
DEVELOPING THIS EVENING WITH LIGHT ACCUMULATIONS POSSIBLE. AREAS
TO BE MOSTLY IMPACTED BY THESE ACCUMULATIONS WILL BE ALONG THE
CONTINENTAL DIVIDE...LEMHI COUNTY AND LOST TRAIL PASS. NORTHWEST MT
VALLEYS WILL NOT BE IMPACTED BY SNOW WITH THIS EVENT...BUT WILL
EXPERIENCE GUSTY NORTHEAST WINDS.
SNOW OVER SOUTHWEST MT AND LEMHI COUNTY WILL CONTINUE STEADILY
THROUGH THE DAY FRIDAY AND INTO SATURDAY WITH SNOW LEVELS LOWERING
TO THE VALLEY FLOORS AND MAY EXPERIENCE LIGHT SNOW ACCUMULATIONS. A
TIGHTENING NORTHEAST TO SOUTHEAST PRESSURE GRADIENT WILL ALLOW
GUSTY NORTHEAST WINDS TO DEVELOP FRIDAY THROUGH SATURDAY...WITH
AREAS OF BLOWING SNOW. IT SHOULD BE NOTED THAT WITH THESE TYPE OF
GUSTY WINDS...OVERNIGHT TEMPERATURES WILL FEEL QUITE BRISK AS THE
WINDS HELP TO LOWER TEMPERATURES INTO THE TEENS. DUE TO THE EARLY
ONSET OF SNOW FOR THIS SEASON...DECIDUOUS TREES RUN THE RISK OF
BROKEN BRANCHES DUE TO ACCUMULATING SNOW. WINTER WEATHER
ADVISORIES HAVE BEEN UPGRADED TO WINTER STORM WARNINGS TO ACCOUNT
FOR THE LONG DURATION OF ACCUMULATING SNOW AND THE POSSIBILITY OF
DAMAGE TO TREES.
THE DEEP LOW PRESSURE SYSTEM WILL DIG AS FAR SOUTH AS UTAH BY
SATURDAY AFTERNOON WITH MOISTURE WRAPPING AROUND IT...CONTINUING
SNOWS OVER SOUTHWEST MT AND LEMHI COUNTY INTO EARLY SUNDAY. BY SUNDAY
AFTERNOON...THE LOW TRACKS INTO EASTERN MT WITH SNOW TAPERING
OFF. ANOTHER VERY COLD NIGHT IS EXPECTED SUNDAY NIGHT...AS CLOUDS
BEGIN TO CLEAR OUT OF THE AREA.
MONDAY THROUGH THURSDAY...A BRIEF DRY PERIOD WILL TAKE HOLD ON MONDAY
AS THE OVERALL WEATHER PATTERN TRANSITIONS FROM THE STRONG UPPER
LEVEL LOW FROM THE PAST WEEKEND TO MORE OF A WESTERLY FLOW FOR THE
REMAINDER OF THE WEEK. THIS TYPE OF FLOW PATTERN TYPICALLY
INDICATES A SHOWERY PRECIPITATION REGIME THAT SHOULD BE CONFINED
MAINLY TO HIGHER TERRAIN.
&&
.AVIATION...A COLD AND WINTRY WEATHER SYSTEM WILL IMPACT THE
NORTHERN ROCKIES BEGINNING THIS EVENING AND CONTINUING THROUGH THE
WEEKEND BEFORE EXITING THE AREA. EASTERLY WINDS WILL INCREASE AND
BECOME GUSTY THIS EVENING AS THE SURFACE PRESSURE GRADIENT
TIGHTENS. WINDS ARE EXPECTED TO REMAIN STRONG THROUGH FRIDAY NIGHT.
SNOW AND BLOWING SNOW WILL IMPACT THE NORTHERN ROCKIES WITH THIS
SYSTEM WITH HEAVIER SNOWFALL EXPECTED NEAR TERMINALS KSMN AND
KBTM. IFR CEILINGS ARE NOT OUT OF THE QUESTION NEAR THESE
TERMINALS AND THEIR VICINITIES UNDER HEAVIER BANDS OF
PRECIPITATION. VISIBILITIES WILL BE REDUCED AT TIMES WITH MOUNTAIN
AND PASS OBSCURATIONS LIKELY.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING FROM 3 AM FRIDAY TO 6 PM MDT SATURDAY FOR
BUTTE/BLACKFOOT REGION.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM MDT
FRIDAY FOR BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM MDT SATURDAY
FOR EASTERN LEMHI COUNTY.
&&
$$
SHORT TERM...ALLEGRETTO
LONG TERM....FELSCH/DEROSA
AVIATION | 
