FXUS65 KGGW 062126
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
226 PM MST SUN DEC 6 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH TUESDAY...

SYNOPTICLY... NORTHEAST MONTANA SETS IN THE MIDDLE OF A STRETCHED
OUT UPPER LEVEL TROUGH WITH THE JET STREAM TO THE SOUTH ACROSS
SOUTHERN WYOMING. UNDERNEATH THIS TROUGH IS A BUBBLE OF COOLER
HIGH PRESSURE NEAR THE SURFACE. LIMITED MOISTURE APPEARS TO BE
OVERRIDING THE TROUGH AND EMBEDDING ITSELF INTO THE AREA ALLOWING
FOR MOSTLY CLOUDY SKIES NEAR THE HORIZONTAL INTERFACE AND LIGHT
SNOW AND OCCASIONAL FLURRIES. THIS HAS TURNED INTO A STAGNANT
PATTERN WHICH IS ANTICIPATED TO CONTINUE THROUGH MONDAY NIGHT WITH
A MOVEMENT OF THE TROUGH FINALLY EJECTING TUESDAY AND PUTTING AN
END TO THE LIGHT FROZEN PRECIP FOR A TIME.

WHILE CLOUD COVER APPEARS TO BE THINNING DURING THE DAYLIGHT
HOURS... OVERNIGHT CONDITIONS ROUTINELY SEE A RETURN TO THIS
CLOUD COVER WHICH IS CURRENTLY DOMINATING SURFACE TEMPERATURES BY
HOLDING IN HEAT. THIS SHOULD CONTINUE TO BE THE NORM UNTIL A
PATTERN CHANGE ARRIVES ON TUESDAY AS 850 MB TEMPERATURES DURING THIS
GROUP OF PERIODS CONTINUES TO STAY IN A RANGE OF -17*C TO -23*C. GAH

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
NO CHANGES TO THE GOING FORECAST AS LITTLE CHANGE INDICATED BY THE
MODELS. COLD AND MOSTLY DRY WEATHER EXPECTED THROUGH THE WEEK AS
STRONG POLAR VORTEX WILL DROP INTO CENTRAL CANADA. SOME MODERATION
OF TEMPERATURES IS POSSIBLE BY NEXT WEEKEND WITH SLIGHT RIDGING
DEVELOPING ON THE WEST COAST. EBERT

PREVIOUS LONG TERM DISCUSSION...A COLD AND MAINLY DRY EXTENDED
FORECAST AS THE POLAR VORTEX CENTERED OVER THE ENVIRONS OF
NORTHWEST HUDSON BAY PERSISTS. THIS WILL KEEP COLD NORTH TO
NORTHWEST FLOW ALOFT ACROSS THE AREA AT LEAST INTO...IF NOT THRU
ALL OF NEXT WEEKEND. GFS ENSEMBLES AND ECMWF ARE IN PRETTY GOOD
AGREEMENT ON THIS BEFORE THE ECMWF GOES OFF IN A DIFFERENT
DIRECTION ROUNDABOUT NEXT SUNDAY OR MONDAY AND THE GFS ENSEMBLES
REALLY START LOOKING LIKE SPAGHETTI CHARTS. THE SAVING GRACE WITH
RESPECT THE COLD MAY BE THE EXPECTED STRATUS CLOUDS THAT WILL
LIKELY PREVAIL THRU MUCH OF WEDNESDAY THRU FRIDAY. ALTHO THEY WILL
KEEP DAYTIME READINGS DOWN...THEY WILL AID IN KEEPING THE BOTTOM
FROM FALLING OUT AT NIGHT...WHICH SURELY WOULD OCCUR IF WE CLEARED
OUT UNDER SUCH A COLD AIRMASS. ALTHO THERE COULD BE SOME
OCCASIONAL LIGHT SNOW...THINK THE SITUATION LOOKS MORE LIKE ONE OF
INTERMITTENT FLURRIES FOR MUCH OF THE PERIOD. CERTAINLY NOTHING
LOOKING EVEN CLOSE TO SIGNIFICANT AT THIS POINT WITH RESPECT TO
ANY SNOWFALL. THERE ARE INDICATIONS OF WARMING BY NEXT SUNDAY OR
MONDAY AS THE MAIN TROF ASSOCIATED WITH THE POLAR VORTEX MOVES FAR
ENUF EAST TO ALLOW SOME UPPER RIDGING OVER THE AREA AS ANOTHER
TROF CARVES SOUTH TOWARD THE WEST COAST. MAIN THRUST OF THE
CHANGES MADE FOR THIS PACKAGE WAS TO LOWER TEMPERATURES MID TO
LATE WEEK.

&&

.AVIATION...
MVFR CONDITIONS SHOULD PREVAIL THROUGH TONIGHT AS LOW CLOUDS AND
LIGHT SNOW/FLURRIES WILL PERSIST FOR MUCH OF THE TIME. THERE WILL
BE PERIODS WHEN CEILINGS RISE TO VFR AND LOWER TO IFR. WIND SHOULD
REMAIN ON THE LIGHT SIDE AND PRIMARILY FROM THE NORTH. RAE

&&

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

&&

$$

WEATHER.GOV/GLASGOW