FXUS65 KTFX 061148
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
445 AM MST SUN DEC 6 2009
AVIATION SECTION UPDATED
.DISCUSSION...
TODAY THROUGH TUESDAY...DEEP NORTHERLY FLOW CONTINUES TO IMPORT AN
INCREASINGLY COLD AIRMASS INTO THE REGION AS NORTHERLY FLOW AROUND
THE BACK SIDE OF AND UPPER UPPER LEVEL TROUGH EXTENDS FROM NEAR THE
NORTH POLE SOUTHWARD THROUGH CENTRAL CANADA AND SOUTHWESTWARD INTO
THE WESTERN UNITED STATES. MOISTURE AND LIFT CONTINUES TO DECREASE
OVER THE ENTIRE AREA...HOWEVER LOW LEVELS WILL REMAIN MOIST FOR
GENERALLY CLOUDY SKIES THROUGH AT LEAST MONDAY AND ANY WEAK
DISTURBANCES WITHIN THE UPPER TROUGH ALONG WITH CONTINUED UPSLOPE
NORTHERLY FLOW WILL PRODUCE VERY LIGHT SNOW SHOWERS OR FLURRIES
ACROSS MOST OF THE AREA. ADDITIONAL ACCUMULATIONS WILL BE MINIMAL
AND THEREFORE THE WINTER STORM WARNING WILL BE ALLOWED TO EXPIRE. A
VERY COLD AIRMASS CONTINUES TO POUR INTO THE REGION FROM THE NORTH
TODAY AND TONIGHT WITH TEMPERATURES EXPECTED TO FALL INTO THE LOW
SINGLE DIGITS ABOVE AND BELOW ZERO BY THIS AFTERNOON...CONTINUING
INTO THE TEENS BELOW AND TWENTIES BELOW ZERO TONIGHT. PRESSURE RISES
AS THE COLD ARCTIC HIGH BUILDS IN WILL SUPPORT BREEZY NORTH WINDS
ACROSS MUCH OF THE AREA PRODUCING VERY LOW WIND CHILLS. WIND CHILL
VALUES ARE EXPECTED TO REACH 20 BELOW TO 35 BELOW ZERO ACROSS
PORTIONS OF NORTH CENTRAL MT BY LATE THIS AFTERNOON WHERE STEADY
NORTH WINDS OF 15 TO 25 MPH WILL PERSIST INTO THIS EVENING.
ELSEWHERE...WINDS OF 10 TO 15 MPH WILL PRODUCE WINDS CHILLS OF 15
BELOW TO 25 BELOW ZERO BY LATER THIS AFTERNOON AND EVENING. WINDS
DIMINISH LATE TONIGHT THROUGH MONDAY MORNING...HOWEVER VERY COLD
OVERNIGHT LOWS OF 15 BELOW TO 25 BELOW ZERO ARE EXPECTED WITH
LOCALLY COLDER AREAS. TEMPS ON MONDAY AFTERNOON WILL LIKELY ONLY
RECOVER TO VALUES SLIGHTLY BELOW ZERO WITH ANOTHER VERY COLD NIGHT
EXPECTED MONDAY NIGHT INTO TUESDAY MORNING. BETTER CHANCES FOR
BREAKS IN THE CLOUD-COVER WILL ALLOW FOR SOME AREAS TO REACH LOWS IN
THE 25 BELOW TO 35 BELOW ZERO OR COLDER RANGE WITH ONLY SLIGHT
RECOVERY AGAIN ON TUESDAY AFTERNOON AS THE ARCTIC AIRMASS REMAIN IN
PLACE OVER THE FORECAST AREA. HOENISCH
TUESDAY NIGHT THROUGH SUNDAY...MODELS IS REASONABLY GOOD AGREEMENT
FOR THE MID-RANGE AND EXTENDED FORECAST PERIODS IN SHOWING GRADUAL
WEAKENING AND EASTWARD SHIFT OF THE DEEP LONGWAVE TROF OVER THE
ROCKIES. THIS WILL EVENTUALLY BRING AN END TO THE BITTERLY COLD
ARCTIC CONDITIONS BUT NOT BEFORE A FEW MORE FRIGID DAYS THROUGH
MIDWEEK. MOISTURE SWINGING SOUTH ALONG THE BACKSIDE OF THE UPPER
LEVEL TROF WILL BRING PERIODS OF LIGHT SNOW ON WED AND THURS...
MAINLY OVER CENTRAL AND NORTH CENTRAL MT...BUT ACCUMULATIONS SHOULD
BE ONLY A FEW INCHES AT MOST AS QPF VALUES ARE LOW. FLOW ALOFT
BEGINS TO SHIFT FROM NORTHWEST TO MORE WESTERLY DIRECTION ON FRI AS
WEAK UPPER LEVEL RIDGING BUILDS OVER THE GREAT BASIN. FRIDAY SHOULD
BE DRY OVER THE REGION BUT MOISTURE AND CHANCES OF LIGHT SNOW
INCREASE AGAIN ACROSS SOUTHWEST MT ON SAT AS NEXT WEATHER SYSTEM
MOVES FROM THE PACIFIC INTO CA/OR. MOISTURE WILL BE SLOW TO SPREAD
EAST OF THE DIVIDE SO PARTS OF CENTRAL MT MAY ONLY SEE INCREASING
CLOUDINESS ON SUN WITH LITTLE/NO SNOW. AS FOR TEMPERATURES...THE
ARCTIC AIRMASS WILL LINGER OVER THE CWA EARLY IN THIS PERIOD. WITH
FAIR AMOUNT OF SNOW COVER PRESENT AND LOW SEASONAL SUN ANGLE...HAVE
ADJUSTED OVERNIGHT LOWS DOWNWARD A FEW DEGREES...KEEPING BELOW ZERO
CONDITIONS THRU WED NIGHT. WIND CHILLS MAY AGAIN REACH 20 DEGREES
BELOW ZERO OR LESS ON TUES NIGHT. GRADUAL WARMUP STARTS ON THURS
BUT IT WILL TAKE A FEW DAYS TO COMPLETELY ERODE THE AIRMASS SO
EXPECT TEMPS TO REMAIN BELOW NORMAL ON THURS & FRI...BUT FINALLY GET
CLOSE TO SEASONAL AVERAGES NEXT WEEKEND. WARANAUSKAS
&&
.AVIATION...
UPDATED 1145Z.
MIX OF VFR-MVFR-IFR CONDITIONS WILL CONTINUE TODAY AS MOIST EASTERLY
FLOW ALOFT IS CAUSING WIDESPREAD UPSLOPE FLOW WITH SCATTERED AREAS
OF LIGHT SNOW. WITH CEILINGS GENERALLY AT FL070 OR LESS...MOST
MOUNTAIN PEAKS WILL BE OBSCURED. WINDS WILL BE PREDOMINANTLY FROM
NORTH-NORTHEAST AT AROUND 10 KTS...BUT EXPECT STRONGER WINDS WITH
GUSTS OF 20 TO 25 KTS FROM KCTB TO KHVR.
WARANAUSKAS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 3 -21 -10 -25 / 100 40 20 10
CTB 1 -25 -11 -35 / 90 30 10 10
HLN 8 -15 -2 -23 / 40 20 10 10
BZN 7 -18 0 -24 / 30 20 20 10
WEY 7 -39 4 -38 / 40 30 20 30
DLN 4 -16 -3 -24 / 30 20 20 10
HVR 9 -13 -6 -20 / 30 20 10 10
LWT 4 -15 -3 -20 / 70 40 20 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 5 AM MST MONDAY FOR MTZ008>015-044>055.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...WARANAUSKAS
AVIATION...SUK
WEATHER.GOV/GREATFALLS
