FXUS65 KTFX 112158
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
258 PM MST FRI DEC 11 2009
.DISCUSSION...
TONIGHT THROUGH SUNDAY...A CLOSED LOW PRESSURE CENTER IS SITUATED
OVER CENTRAL CANADA AND KEEPING NORTHWEST FLOW ALOFT OVER THE ZONES.
THE SURFACE PRESSURE GRADIENT IS WEAKENING AND WINDS HAVE DECREASED.
MAIN INTEREST IS THE CANADIAN COLD FRONT WHICH WILL BE CROSSING THE
BORDER EARLY SATURDAY AND THROUGH CENTRAL MONTANA BY THE AFTERNOON.
ASSOCIATED SNOW SHOULD MOVE INTO THE HILINE EARLY IN THE MORNING AND
INTO THE CENTRAL ZONES BY AFTERNOON. COLD TEMPERATURES WILL FOLLOW
AND WIND CHILLS BELOW MINUS 20 WILL DEVELOP BY SATURDAY EVENING.
BEST MOISTURE APPEARS OVER THE NORTHEAST ZONES BUT UPSLOPE FLOW
SHOULD BE STEADY AND PRECIP WILL BE WIDESPREAD. EXPECT ACCUMULATIONS
SHOULD REMAIN NEAR ADVISORY CRITERIA WITH LOCALLY HEAVY MOUNTAIN
SNOW. WIND SPEEDS SHOULD WEAKEN BY MIDNIGHT SUNDAY ALTHOUGH THE
MOIST...EAST FLOW WILL CONTINUE THROUGH SUNDAY. TO THE SOUTH...A
SHORTWAVE MOVING ACROSS NEVADA WILL AFFECT SOUTHWEST MONTANA
SATURDAY AFTERNOON. AT THE MOMENT...MOST PRECIP WILL BE OVER THE
SOUTHERN MOUNTAINS AND WILL NOT ISSUE ANY HIGH LIGHTS AT THIS
MOMENT. ZELZER
SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...PERIOD BEGINS WITH ANOTHER
SHOT OF ARCTIC AIR PUSHING ACROSS THE AREA. IT ALSO APPEARS THE BEST
TIMING FOR SNOW WILL BE SUNDAY EVENING AND OVERNIGHT. THIS IS A VERY
QUICK HITTING SYSTEM WITH SNOW AMOUNTS LESS THAN RECEIVED DURING THE
LAST EVENT. SCATTERED SNOW WILL TAPER OFF ON MONDAY. BY TUESDAY AN
UPPER RIDGE BEGINS TO MOVE IN FROM THE WEST ERODING THE SHALLOW
ARCTIC AIR AND PUSHING AFTERNOON TEMPERATURES INTO THE 20S. WEAK
IMPULSES MOVING THROUGH THE RIDGE ON WEDNESDAY WILL BRING ISOLATED
SNOW TO THE WESTERN AND SOUTHWEST PORTIONS OF THE COUNTY WARNING
AREA. TEMPERATURES WILL BE WELL BELOW SEASONAL AVERAGES MONDAY BUT A
WARMING TREND WILL COMMENCE ON TUESDAY WITH AFTERNOON READINGS
REACHING NEAR SEASONAL AVERAGES BY WEDNESDAY.
THURSDAY THROUGH FRIDAY...MODELS ARE IN ROUGH AGREEMENT DURING THIS
PERIOD...WITH SOME DIFFERENCE IN TIMING AND STRENGTH OF FEATURES. A
WEAK UPPER LEVEL RIDGE OVER THE PACIFIC NORTHWEST DRIFTS EASTWARD
ACROSS THE REGION. A FEW DISTURBANCES RIDING OVER THE RIDGE
CONTRIBUTE TO A CHANCE OF SNOW OVER THE MOUNTAINS WITH A SLIGHT
CHANCE OF RAIN OR SNOW OVER THE WESTERN PLAINS AND MOST VALLEYS.
DOWNSLOPE WINDS WILL BE GUSTY OVER NORTH CENTRAL MONTANA AND WILL
HELP LIMIT THE CHANCE OF PRECIPITATION OVER THE PLAINS AND LARGER
VALLEYS. TEMPERATURES WILL BE WARMING ABOVE SEASONAL AVERAGES FOR
MOST LOCATIONS. EK
&&
.AVIATION...
UPDATED 1800Z.
NORTHWEST FLOW ALOFT WILL CONTINUE WITH ISOLATED SNOW SHOWERS
POSSIBLE OVER THE MOUNTAINS. WEST TO SOUTHWEST SURFACE WINDS
WILL REMAIN BREEZY...ESPECIALLY ALONG THE ROCKY MOUNTAIN FRONT AND
ADJACENT PLAINS. VFR CONDITIONS WILL PREVAIL WITH MVFR CONDITIONS
POSSIBLE IN THE VICINITY OF SNOW SHOWERS. EXPECT OCCASIONAL MOUNTAIN
OBSCURATION ALONG THE CONTINENTAL DIVIDE AS WELL. ANOTHER WINTER
STORM WILL APPROACH THE REGION AT THE END OF THE CURRENT FORECAST
PERIOD FOR NORTHERN AIRFIELDS. THE SYSTEM IS EXPECTED TO BRING
ACCUMULATING SNOW AND ARCTIC AIR BACK TO THE REGION.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 18 22 -7 -5 / 20 60 70 70
CTB 11 11 -18 -12 / 20 80 70 70
HLN 12 22 2 7 / 10 60 70 70
BZN 5 27 12 17 / 20 40 50 70
WEY -1 22 13 27 / 40 90 90 90
DLN 8 28 13 29 / 20 50 50 60
HVR 8 11 -17 -12 / 20 60 70 60
LWT 10 22 -10 -3 / 20 50 60 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY
EVENING FOR BLAINE...CASCADE...CENTRAL AND SOUTHERN LEWIS AND
CLARK...CHOUTEAU...EASTERN GLACIER...EASTERN PONDERA...EASTERN
TETON...FERGUS...HILL...JUDITH BASIN...LIBERTY...NORTHERN ROCKY
MOUNTAIN FRONT...SOUTHERN ROCKY MOUNTAIN FRONT...TOOLE.
&&
$$
WEATHER.GOV/GREATFALLS
