FXUS65 KGGW 060343
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
843 PM MST SAT DEC 5 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
UPDATED THE SHORT TERM FORECAST THIS EVENING TO DROP ALL WINTER WEATHER
HIGHLIGHTS FROM THE ZONES AND LOWER THE CHANCE OF PRECIPITATION
ACROSS THE REGION. SNOWFALL CAME TO AN END ACROSS THE CWA EXCEPT FOR
FAR SOUTHWEST PETROLEUM COUNTY THIS EVENING...WHICH WAS ONLY
REPORTING VERY LIGHT SNOW AND FLURRIES. THIS WILL CONTINUE OFF AND
ON ACROSS EXTREME WESTERN AND SOUTHERN ZONES OVERNIGHT WITH NO
ADDITIONAL ACCUMULATION EXPECTED. WE DID HAVE SOME CLEARING IN THE
CLOUD COVER TO THE NORTH AND EAST. LOOKING AT THE GOES FOG/IR
SATELLITE LOOP A LOW LAYER OF STRATUS CLOUDS IS MOVING SOUTHWARD
OUT OF SASKATCHEWAN AND THERE MIGHT BE SOME ISOLATED FLURRIES
UNDER THIS BAND OF CLOUDS BUT NOTHING SIGNIFICANT IS EXPECTED. THE
REST OF THE SHORT TERM FORECAST LOOKS GOOD. RSMITH
PREVIOUS DISCUSSION...A WINTER WEATHER ADVISORY IS IN EFFECT FOR
PETROLEUM AND SOUTHWESTERN PHILLIPS COUNTY FROM 09Z SATURDAY
THROUGH 12Z SUNDAY. THE WINTER WEATHER ADVISORY FOR NORTHERN AND
CENTRAL PHILLIPS ALONG WITH GARFIELD COUNTY HAVE BEEN CAN CANCELED.
CONTINUE READING FOR FURTHER DETAILS.
TONIGHT THROUGH SUNDAY EVENING... THE SECOND WAVE OF FROZEN PRECIPITATION
SHOULD MAKE IT INTO SOUTHWESTERN PORTIONS OF THE CWA BY THE
AFTERNOON AND EVENING. A EAST SOUTH EAST TO WEST NORTH WEST
ALIGNED CLEARING LINE HAS APPEARED ON RADAR TRENDS ACROSS CENTRAL
PORTIONS OF THE CWA. FURTHER BEHIND IT IS CLEAR SKIES WHICH ARE OBSERVABLE
ON SATELLITE TRENDS AND WEBCAM IMAGES. THIS CLEARING IS ASSOCIATED
WITH VERY DRY... COLD HIGH PRESSURE WHICH IS SLIDING INTO
NORTHEASTERN PORTIONS OF THE CWA AND SHOULD CONTINUE THROUGH THE
SUNDAY. THE CLEARING LINE SHOULD STALL JUST NORTH OF OUR BORDER
WITH BYZ SUNDAY WHILE A SMALL AMOUNT OF LIGHT SNOW AND FLURRIES
WILL STILL IMPACT SOUTHEASTERN PORTIONS OF THE CWA THROUGH SUNDAY
EVENING. LOWS TONIGHT ACROSS THE NORTHEAST HAVE THE POTENTIAL TO
DROP BEYOND THE LOWEST GUIDANCE OF THE MEL DATA DUE TO CLEARING
SKIES... LIGHT NORTHERN WINDS... AND CAA FROM A NEWLY DEVELOPED
SNOW PACK ACROSS SOUTHERN SASKATCHEWAN. MEN TO MEL DATA SEEM TO
HAVE CAUGHT ON TO THIS TREND FOR A VERY SIMILAR SUNDAY NIGHT.
MONDAY...EXPECT HIGH PRESSURE AND DRY CONDITIONS TO BE WELL
ESTABLISHED AT THE SURFACE WITH UPPER LEVEL PATTERNS IN MODELS
SHOWING US TO BE IN BETWEEN SIGNIFICANT LOW PRESSURE SYSTEMS. 850
MB TEMPERATURES ESTABLISH THE BITTER COLD OF -15 TO -20*C
THROUGHOUT THE PERIOD AND BEYOND. THIS SHOULD TRANSLATE INTO
DAYTIME HIGHS NEAR ZERO. GAH
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
COLD AND MOSTLY DRY WEATHER STILL EXPECTED TO PERSIST THROUGH NEXT
WEEK. LITTLE CHANGE IN THE MODELS WITH POLAR VORTEX DROPPING INTO
CENTRAL CANADA AND DOMINATING THE FLOW ACROSS NORTH AMERICA SO NO
CHANGE TO THE GOING FORECAST. EBERT
PREVIOUS LONG TERM DISCUSSION...PERIOD BEGINS MONDAY NIGHT WITH
AN UPPER TROF EXTENDING FROM HUDSON BAY SOUTHWESTWARD THRU THE
GREAT BASIN. VERY COLD AIR IS EXPECTED TO BE IN PLACE WITH 850 MB
TEMPERATURES IN THE VICINITY OF -22 DEGREES CELSIUS. WITH A
SURFACE HIGH IN PLACE AND ALL OF THE UPPER SUPPORT WELL SOUTH OF
THE AREA THINGS LOOKING DRY WITH A GOOD CHANCE OF A LOW CLOUDS
FIELD ACROSS THE AREA. ON TUESDAY THE MAIN POLAR VORTEX REMAINS
OVER NORTHERN HUDSON BAY WITH THE ASSOCIATED TROF NOW BEGINNING TO
SWING EAST. HOWEVER THE COLD AIR STILL REMAINS WELL ENTRENCHED
OVER THE AREA. SO ANOTHER DRY BUT LIKELY MOSTLY CLOUDY AND COLD
DAY. MAIN UPPER TROF AXIS FINALLY MOVES INTO THE PLAINS TUESDAY
NIGHT WITH SOME VERY WEAK WARM AIR ADVECTION ALOFT. STILL DECENT
SURFACE HIGH PRESSURE OVERHEAD WITH LITTLE MIXING SO THAT WARM AIR
IS LIKELY STAY ALOFT MAKING FOR ANOTHER BELOW NORMAL TEMPERATURE
NIGHT. SOME POSSIBLE CLEARING COULD MAKE FOR AN EVEN COLDER NIGHT.
MORE WARM AIR ADVECTION ALOFT WEDNESDAY WITH NORTH NORTHWEST FLOW
ALOFT AND THE DEPARTING UPPER TROF MOVES A BIT FARTHER AWAY TO THE
EAST. MODELS AT THIS POINT TO INDICATING MUCH IN THE WAY OF
SURFACE OR LOW LEVEL FEATURES TO PROVIDE ANY REALLY GOOD
MIXING...SO THE SURFACE WARMUP LIKELY TO RELATIVELY MINIMAL. STILL
NOTHING REALLY POINTING TO ANY SIGNIFICANT PRECIPITATION...PERHAPS
FLURRIES AS IT APPEARS A DECENT STRATUS FIELD LOOMS ALTHO THERE IS
LITTLE UPPER SUPPORT. THAT SITUATION APPEARS TO PERSIST THRU
WEDNESDAY NIGHT AND THURSDAY...ALTHO THURSDAY A BIT MORE MIXING
MAY BE HAD WITH SOME SEMBLANCE OF A SURFACE TROF. GFS ENSEMBLES
PRETTY MUCH AGREE ON THINGS THRU THIS POINT. ECMWF IS SLOWER IN
BRINGING THE UPPER TROF THRU AS IT MIGRATES THE CANADIAN POLAR
VORTEX FARTHER WEST ACROSS THE NORTHERN TERRITORIES THAN DOES THE
OPERATIONAL GFS OR ENSEMBLES. FOR NOW THE ECMWF SOLUTION SEEMS A
BIT OF AN OUTLIER. LATE IN THE WEEK INTO NEXT WEEKEND THE UPPER
FLOW ACROSS THE UNITED STATES BEGINS TO FLATTEN OUT ACCORDING TO
THE GFS ENSEMBLE MEMBERS. WHERE THEY DIFFER IS JUST HOW WARM OR
COLD IT MIGHT BE AS THERE IS QUITE THE SPREAD WITH RESPECT TO 850
MB TEMPERATURES AND HEIGHT/THICKNESS VALUES. AS FAR AS
PRECIPITATION GOES...THINGS STILL LOOK MOSTLY DRY.
&&
.AVIATION...
VFR CONDITIONS THIS EVENING WILL GRADUALLY GIVE WAY TO LOW
MVFR/IFR AS LOW STRATUS CLOUDS MOVE IN. LIGHT SNOW OR FLURRIES MAY
REDUCE VISIBILITIES INTO THE MVFR RANGE SUNDAY AFTERNOON. JAMBA
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
