FXUS65 KGGW 080324
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
824 PM MST MON DEC 7 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH WEDNESDAY...
UPDATES TO LOWER TEMPS AND ADD MENTION OF SCATTERED FLURRIES FOR
THE SE ZONES FOR TONIGHT AND TUESDAY. WAS WEARY OF WIND CHILLS
BEING A PROBLEM FOR THE SE ZONES AS NAM BRINGS IN A PRESSURE
GRADIENT THERE BUT GFS KEEPS IT FURTHER SOUTH. GFS SEEMS TO BE
INITIALIZING BETTER RIGHT NOW BUT WILL KEEP A WATCH ON IT. MAINLY
LOWERED TEMPS ACROSS THE NORTH AND WEST AS CLEAR SKIES AND LIGHT
WINDS SHOULD TAKE TEMPS WELL BELOW GUIDANCE...CLOSE TO -25 IN MANY
PLACES. REST OF FORECAST LOOKED GOOD. JAMBA

PREVIOUS DISCUSSION...
BROAD LONG WAVE TROF OVER NORTH AMERICA WITH SHORTWAVE MOVING
INTO THE GREAT BASIN THIS AFTERNOON. THIS SHORTWAVE WILL SLIDE
EASTWARD THROUGH THE FOUR CORNERS AND INTO THE CENTRAL PLAINS
DURING THE SHORT TERM. MOISTURE EXPECTED TO SPREAD NORTH INTO
SOUTHERN MONTANA WHILE DRY AIR WORKS SOUTH FROM CANADA. 

DOMINANCE OF THE ARCTIC HIGH IN SOUTHERN SASKATCHEWAN WILL
CONTINUE TONIGHT...AND WITH CLEARING SKIES EXPECT TEMPERATURE TO
AGAIN PLUMMET TO NEAR 20 BELOW IN THE NORTHWEST WHILE THE
YELLOWSTONE VALLEY WILL REMAIN A LITTLE WARMER. AS THE SOUTHERN
STORM MOVES FROM THE MOUNTAINS INTO THE PLAINS ON TUESDAY...THE
CANADIAN HIGH WILL FILTER FURTHER SOUTH KEEPING NORTHEAST MONTANA
COLD INTO TUESDAY NIGHT. A SECOND SHORTWAVE DIVES SOUTH ALONG THE
CANADIAN ROCKIES ON WEDNESDAY...PULLING ANOTHER SURGE OF COLD AIR
SOUTH...AND COULD BRING A SHOT OF FLURRIES OR LIGHT SNOW AS WELL.
EBERT 

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
WEDNESDAY NIGHT THROUGH FRIDAY... THE LONG WAVE TROUGH PATTERN
ACROSS THE NORTH AMERICAN CONTINENT IS ANTICIPATED TO FINALLY
BEGIN TO LIFT TO THE EAST. THIS WILL PLACE US BRIEFLY IN
TRANSITION FROM NORTHWEST FLOW TO INCREASING ZONAL FLOW AND A
SLIGHT WINTER RELATIVE SLIGHT WARM UP. BRIEF FLURRIES MAY BE
POSSIBLE WITH THE EXIT OF THIS SYSTEM ON WEDNESDAY NIGHT THROUGH
THURSDAY BUT SKIES SHOULD QUICKLY CLEAR INTO THURSDAY NIGHT AND
FRIDAY.

FRIDAY NIGHT THROUGH SUNDAY... THE THE TEETER TOTTERING JAVELIN
KNOWN AS POLAR VORTEX SLAMS DOWN THE FRONT RANGE AND INTO THE CWA
BRINGING A RETURN TO BITTERLY COLD ARCTIC TEMPERATURES. PACIFIC
MOISTURE IS ANTICIPATED TO BE LIFTED ACROSS THE AREA BY A MID
LEVEL TROUGH WHOSE AXIS IS ORIENTED NORTHWEST TO SOUTHEAST ACROSS
THE INTERMOUNTAIN WEST. THIS WILL PROVIDE AMPLE MOISTURE AND LIFT
TO GENERATE AT LEAST SOME LIGHT SNOW. DUE TO THE EXTREME
TEMPERATURES GRADIENT THAT WILL BE ORIENTED WITH THE PASSAGE OF THIS
POLAR VORTEX EXPECT THAT PRESSURE GRADIENTS AND THEREFORE WINDS
WILL BE FAIRLY STRONG WITH THE PASSAGE OF THIS SYSTEM. HOWEVER THE
MESOSCALE PLACEMENT AND TIMING OF THIS SYSTEM'S WINDS AND
TEMPERATURE GRADIENTS IS STILL TOO AMBIGUOUS TO DETERMINE AND WILL
REQUIRE FUTURE MODEL RUNS AND ANALYSIS TO PIN DOWN. 

SUNDAY NIGHT THROUGH MONDAY NIGHT... COLD AIR ACROSS THE REGION IS
ANTICIPATED TO SHALLOW OUT WITH A SLOW WARM UP AND CLEARING SKIES
AND HIGH PRESSURE NEAR THE SURFACE.

PREVIOUS LONG TERM DISCUSSION...
WILL CONTINUE TO HOLD THE PREVIOUS COURSE OF A MAINLY DRY AND
COLD FORECAST. POLAR VORTEX CENTERED NORTH OF SASKATCHEWAN
WEDNESDAY NIGHT THRU THURSDAY NIGHT KEEPS COLD NORTH TO NORTHWEST
FLOW ACROSS THE AREA. THERE MAY BE SOME FLURRIES AT TIMES BUT NOT
SEEING ANY BIG REASONS FOR ANY SNOW DEEMED SIGNIFICANT. ECMWF AND
GFS MODELS BEGIN TO DRIFT APART A BIT AFTER THAT AND GFS ENSEMBLE
MEMBERS BEGIN TO SHOW MORE SPREAD. OPERATIONAL GFS SEEMS A BIT
SUSPECT IN ITS RATHER FAST MOVEMENT OF THE CANADIAN LOW COMPARED
WITH THE ECMWF AND THE BULK OF THE ENSEMBLE MEMBERS. WILL CONTINUE
TO RIDE ALONG WITH A COLD FORECAST AS LOW LEVEL COLD AIR REMAINS
IN THE WAKE OF THE CANADIAN LOW FINALLY ROTATING CYCLONICALLY AND
KICKING EAST TO HUDSON BAY BY SATURDAY AFTERNOON. SURFACE HIGH
EXPECTED OVER NORTHEAST MONTANA SHOULD NOT ALLOW FOR MUCH IN THE
WAY OF MIXING WHICH LOOKS TO BE FORTUNATE AS COLD AIR REMAINS IN
THE LOWER LEVELS ANYWAY. UPPER FLOW BECOMES ZONAL FOR SUNDAY AND
MONDAY BEFORE PERHAPS SOME WEAK TO VERY WEAK UPPER RIDGING MOVES
IN FOR TUESDAY.

&&

.AVIATION...
EXPECT A RANGE OF VFR TO MVFR CONDITIONS DUE TO LOW CLOUDS
OVERNIGHT...WITH MOST OF THE LOW CLOUDS MOVING IN FROM THE
SOUTHWEST. THE MVFR CONDITIONS WILL START AT KGDV...KSDY THEN
POSSIBLY SPREAD NORTHWARD TO THE KGGW AND KOLF BY MORNING. THE
WINDS WILL REMAIN LIGHT OUT OF THE EAST AT ALL TERMINALS
OVERNIGHT. CONDITIONS WILL BECOME VFR IN THE MORNING AND REMAIN
THAT WAY THE REST OF THE DAY. ALSO EXPECT LIGHT NORTHEAST WIND AT
ALL TERMINALS DURING THE AFTERNOON. RSMITH

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

WEATHER.GOV/GLASGOW