FXUS65 KTFX 101802
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 AM MST THU DEC 10 2009
.UPDATE...
TODAY...SEVERAL DISTURBANCES WILL CONTINUE TO MOVE THROUGH THE
NORTHWEST FLOW ALOFT. THE CURRENT DISTURBANCE WILL BE MOVING
SOUTH OF THE ZONES LATER THIS AFTERNOON. IN THE MEAN TIME...LIGHT
SNOW IS POSSIBLE WITH THE MODELS DEVELOPING THE BEST LIFT SOUTH
OF KGTF THROUGH GALLATIN COUNTY. WARM ADVECTION WILL CONTINUE
TODAY AND TEMPS HAVE RISEN QUICKLY IN SOME LOCATIONS. WILL UPDATE
TO RAISE SEVERAL TEMPS AND FRESHEN FIRST PERIOD. ZELZER
&&
.AVIATION...
UPDATED 1800Z.
NORTHWEST FLOW ALOFT WILL PERSIST. BREEZY SURFACE WINDS WILL
CONTINUE ALONG THE ROCKY MOUNTAIN FRONT AS WELL AS OVER THE PLAINS.
WINDS WILL SLOWLY DIMINISH THIS AFTERNOON. THERE IS ENOUGH
INSTABILITY WITHIN THE NORTHWEST FLOW ALOFT FOR ISOLATED SNOW
SHOWERS BUT THESE WILL OCCUR MAINLY OVER HIGHER TERRAIN. VFR
CONDITIONS WILL PREVAIL WITH MVFR CONDITIONS IN THE VICINITY OF
SNOW SHOWERS AS WELL AS OCCASIONAL MOUNTAIN OBSCUREMENT.
&&
.PREV DISCUSSION...
/ISSUED 440 AM MST THU DEC 10 2009/
TODAY THROUGH SATURDAY...COLD/CYCLONIC NW FLOW ALOFT WILL PERSIST
OVER THE REGION INTO THIS WEEKEND AS A BROAD UPPER TROUGH OVER
MUCH OF NORTH AMERICA GRADUALLY LIFTS NORTHWARD AS THE PARENT
UPPER LEVEL LOW OVER CENTRAL CANADA ELONGATES. SURFACE PRESSURE
WILL CONTINUE GRADUALLY LOWER ACROSS THE FORECAST AREA THROUGH
FRIDAY...MAINTAINING DOWNSLOPE PRESSURE GRADIENTS AND BREEZY TO
WINDY CONDITIONS OVER THE PLAINS TODAY AND TOMORROW. STRONGEST
WINDS WILL LIKELY BE TODAY FOR AREAS ALONG THE IMMEDIATE EAST
SLOPES OF THE ROCKIES. MOST OF THE AREAS THAT ARE EXPERIENCING
WINDS HAVE ALSO SEEN TEMPERATURES RISE TO SUFFICIENT VALUES TO
KEEP WIND CHILLS ABOVE -20 AND THEREFORE AM NOT EXPECTING THE NEED
FOR ANY ADDITIONAL WIND CHILL HIGHLIGHTS THROUGH THE NEXT SEVERAL
DAYS. TEMPERATURES CONTINUE TO WARM TODAY AND FRIDAY BUT REMAIN
BELOW SEASONAL AVERAGES. LIMITED MOISTURE AND WEAK DISTURBANCES IN
THE NW FLOW ALOFT WILL BRING SOME LIGHT SNOW SHOWERS...MAINLY TO
THE MTNS TODAY AND AGAIN TOMORROW WITH LITTLE OR NO ACCUMULATION
EXPECTED. AN UPPER LEVEL TROUGH MOVING ONSHORE AND INTO THE GREAT
BASIN FRIDAY NIGHT WILL SPREAD ADDITIONAL MOISTURE AND BETTER
CHANCES FOR LIGHT SNOW INTO FAR SW MT ZONES BY LATE SATURDAY. THIS
SYSTEM WILL ALSO ALLOW FOR LOWERING SURFACE PRESSURE WEST OF
DIVIDE FRIDAY NIGHT AND SATURDAY...WHICH WILL WEAKEN PRESSURE
GRADIENTS AND ALLOW FOR LESSER WINDS ACROSS NORTH CENTRAL MT BY
SATURDAY. HOENISCH
SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODELS CONTINUE TO
EXHIBIT GENERAL SIMILARITIES DURING THE PERIOD. A CLOSED UPPER LOW
OVER NORTHERN CANADA WILL PUSH A LARGE AREA OF MOISTURE SOUTH ACROSS
THE INTERNATIONAL BORDER ON SUNDAY WHERE IT WILL MERGE WITH
MOISTURE WORKING ITS WAY NORTH FROM THE SOUTHWEST US. THE RESULT
WILL BE SCATTERED SNOW OVER MOST OF THE COUNTY WARNING AREA. A
SURFACE COLD FRONT WILL ALSO BEGIN TO MOVE ACROSS THE AREA SUNDAY
BRINGING COLDER AIR AS FAR SOUTH AND WEST AS GREAT FALLS. SCATTERED
SNOW AND COLD WILL CONTINUE ON MONDAY AS THE AREA REMAINS UNDER
NORTHWEST FLOW ALOFT...BETWEEN A BUILDING UPPER RIDGE OVER THE
PACIFIC NORTHWEST AND THE UPPER LOW MOVING EAST ACROSS CANADA. THE
REMAINDER OF THE PERIOD WILL SEE A DRYING AND WARMING TREND AS A
WEAK UPPER RIDGE MOVES ACROSS THE CONTINENTAL DIVIDE BY THURSDAY.
ISOLATED SNOW SHOWERS WILL REMAIN A POSSIBILITY FOR THE WESTERN
MOUNTAINS AS WELL AS THE MOUNTAINS OF SOUTHWEST MONTANA.
TEMPERATURES WILL REMAIN BELOW SEASONAL AVERAGES.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 19 7 28 11 / 20 10 10 20
CTB 15 4 23 10 / 10 10 20 30
HLN 18 -1 18 4 / 20 10 10 10
BZN 15 -10 14 0 / 20 10 0 10
WEY 7 -14 13 6 / 30 20 10 60
DLN 14 -6 18 5 / 10 10 0 10
HVR 18 4 19 -1 / 20 10 20 30
LWT 16 4 26 6 / 30 20 10 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
