AREA FORECAST DISCUSSION

 
 FXUS65 KTFX 241648
 AFDTFX
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE GREAT FALLS MT
 948 AM MST TUE NOV 24 2009
 
 .UPDATE...
 PACIFIC MOISTURE WILL CONTINUE TO PROPAGATE OVER UPPER-LEVEL RIDGE
 RESULTING IN PERSISTENT MID-HIGH CLOUD COVER THROUGHOUT THE DAY.
 STRONG DOWNSLOPING WINDS WILL LIMIT PRECIP OVER THE VALLEYS AND
 PLAINS...HOWEVER ISOLATED RAIN AND/OR SNOW SHOWERS ARE POSSIBLE IN
 THE MOUNTAINS SO HAVE LEFT HIGHER CHANCE POPS IN THE FORECAST.
 INCREASED HIGH TEMPS OVER THE PLAINS BASED ON CURRENT OBSERVATIONS
 HOWEVER LIMITED SUNSHINE SHOULD PREVENT RAPIDLY RISING
 TEMPERATURE READINGS. ALSO CANCELLED HIGH WIND WARNING FOR THE
 ROCKY MOUNTAIN FRONT AND EASTERN GLACIER COUNTY AS HIGH WIND
 THREAT HAS DIMINISHED OVER THE AREA. REMAINDER OF THE FORECAST IS
 RIGHT ON TRACK SO MADE NO FURTHER UPDATES THIS MORNING. MLS
 
 &&
 
 .AVIATION...
 UPDATED 1155Z. 
 EXPECT GENERALLY VFR CONDITIONS THROUGH THE PERIOD. EXPECT SCATTERED 
 SNOW SHOWERS OVER THE MOUNTAINS WITH THE POSSIBILITY OF MOUNTAIN TOP 
 OBSCUREMENT AT TIMES. ALTHOUGH AM CONFIDENT OF VFR CONDITIONS FOR 
 THE LOWER ELEVATIONS DO NOT HAVE CONFIDENCE IN EXACT CEILING HEIGHTS 
 WHICH COULD RANGE FROM 5000 FT TO 25000 FT. FEEL PRETTY GOOD ABOUT 
 GUSTY WINDS FORECAST IN THE TAFS THROUGH THIS AFTERNOON. BLANK 
 
 &&
 
 .PREV DISCUSSION...
 /ISSUED 455 AM MST TUE NOV 24 2009/
 
 TODAY THROUGH THANKSGIVING DAY...THE WESTERLY FLOW ALOFT WILL
 INCREASE FURTHER THROUGH THIS MORNING AS AN UPPER LEVEL SHORTWAVE
 TROUGH APPROACHES THE TFX CWA FROM THE NORTHWEST OUT OF
 SOUTHWESTERN CANADA. THIS SHORTWAVE WILL MAINLY MOVE ACROSS NORTH
 CENTRAL AND CENTRAL MONTANA AND BRING NUMEROUS SNOW SHOWERS TO THE
 WESTERN MONTANA MOUNTAINS THROUGHOUT THE DAY. THE STRONG WINDS
 OVER RIDGE TOPS AND THROUGH MOUNTAIN PASSES WILL CAUSE AREAS OF
 BLOWING SNOW THERE AS WELL. THERE WILL ONLY BE SCATTERED MAINLY
 MOUNTAIN SNOW SHOWERS IN SOUTHWEST MONTANA DUE TO THIS MORE
 NORTHERLY TRACK. THE RESULTING WESTERLY DOWNSLOPE WINDS THIS
 MORNING WILL LIMIT PRECIPITATION OVER THE PLAINS OF NORTH CENTRAL
 AND CENTRAL MONTANA AS WELL. THE STRONGEST WINDS WILL BE ALONG THE
 ROCKY MOUNTAIN FRONT AND INTO EASTERN GLACIER COUNTY. FORECAST
 MODELS AND OVERNIGHT OBSERVATIONS INDICATE THAT WINDS HAVE BEEN
 AND WILL NOT BE QUITE AS STRONG AS ORIGINALLY EXPECTED...BUT
 OCCASIONAL GUSTS COULD STILL REACH HIGH WIND CRITERIA THROUGH THE
 MORNING. WINDS WILL DECREASE IN THE AFTERNOON AS THE WINDS ALOFT
 WEAKEN AND SHIFT MORE NORTHWESTERLY. HOWEVER...THIS SHIFT WILL
 BRING ISOLATED SHOWERS TO THE MORE NORTH FACING SLOPE AREAS OF
 CENTRAL MONTANA...MAINLY EAST OF GREAT FALLS. THE UPPER LEVEL
 RIDGE OF HIGH PRESSURE ALONG THE PACIFIC COAST WILL BUILD EAST
 INTO THE STATE AGAIN TONIGHT THROUGH THANKSGIVING DAY.
 INITIALLY...THE MOIST NORTHWEST FLOW ALOFT WILL BRING A CHANCE OF
 SNOW SHOWERS TO THE MOUNTAINS TONIGHT...BUT DRY CONDITIONS WILL
 PREVAIL THROUGH THE REMAINDER OF THE PERIOD. TEMPERATURES WILL BE
 ABOUT 4 TO 7 DEGREES ABOVE NORMAL TODAY...THEN THEY WILL GRADUALLY
 WARM INTO THE 50S AND LOWER 60S BY THANKSGIVING DAY (15 TO 20
 DEGREES ABOVE NORMAL). BREEZY AND GUSTY SOUTHWEST TO WEST WINDS
 WILL ALSO PERSIST THROUGH MOST OF THE PERIOD ACROSS NORTH CENTRAL
 AND CENTRAL MONTANA.  COULSTON
 
 THURSDAY NIGHT THROUGH TUESDAY NIGHT...PROGRESSIVE PATTERN TO
 CONTINUE. AN UPPER TROUGH WILL MOVE THROUGH THE FORECAST AREA
 LATE THIS WEEK OR EARLY IN THE WEEKEND. MODELS DIFFER ON THE
 TIMING OF THIS UPPER TROUGH BUT IT APPEARS THE MOST LIKELY TIMING
 WILL BRING IT THROUGH FRIDAY NIGHT. THIS FEATURE MOVES THROUGH
 FAIRLY QUICKLY AND IS NOT ALL THAT STRONG SO INHERITED CHANCES OF
 PRECIPITATION IN THE SLIGHT CHANCE TO CHANCE CATEGORY FOR THE
 LOWER ELEVATIONS LOOKS FINE. BEST THREAT FOR PRECIPITATION WITH
 THIS SYSTEM APPEARS TO BE OVER THE MOUNTAINS OF THE ROCKY
 MOUNTAIN FRONT SO WENT WITH CHANCES OF PRECIPITATION IN THE
 LIKELY CATEGORY THERE. AFTER THE PASSAGE OF THE UPPER TROUGH
 THERE COULD BE SOME LINGERING MOISTURE AND POSSIBLY A WEAK
 WEATHER DISTURBANCE OR TWO IN THE NORTHWEST TO NORTH FLOW ALOFT
 SATURDAY AND SATURDAY NIGHT SO WILL CONTINUE WITH A MENTION OF
 PRECIPITATION. THEN ANOTHER UPPER TROUGH IS EXPECTED TO MOVE
 THROUGH THE AREA EARLY NEXT WEEK. THE PREVIOUS RUN OF THE GFS
 COMPUTER MODEL WAS QUITE A BIT FASTER THAN THE ECMWF COMPUTER RUN
 WITH THE UPPER TROUGH BUT THE LATEST GFS RUN IS NOW IN RELATIVELY
 BETTER AGREEMENT WITH THE ECMWF COMPUTER RUN. WHEREAS THE UPPER
 TROUGH OF LATE THIS WEEK WILL BE OF PACIFIC ORIGIN THE UPPER
 TROUGH OF EARLY NEXT WEEK WILL COME FROM THE GULF OF ALASKA AND
 WILL LIKELY BE COLDER. AS MODELS HAVE NOT BEEN CONSISTENT ON THIS
 COOL DOWN DID NOT GO REALLY COLD BUT THERE IS THE POTENTIAL FOR
 TEMPERATURES TO BE 10 DEGREES COLDER THAN CURRENT FORECASTS.
 BLANK
 
 &&
 
 .PRELIMINARY POINT TEMPS/POPS...
 GTF  47  30  54  39 /  10  10   0   0 
 CTB  45  28  52  37 /  10  10   0   0 
 HLN  44  24  49  28 /  20  10   0   0 
 BZN  38  17  43  18 /  10  20   0   0 
 WEY  30  10  34  13 /  10  10  10   0 
 DLN  39  20  43  24 /  10  10   0   0 
 HVR  48  17  51  31 /  10  10   0   0 
 LWT  43  19  48  30 /  20  20   0   0 
 
 &&
 
 .TFX WATCHES/WARNINGS/ADVISORIES...
 NONE.
 &&
 
 $$
 
 WEATHER.GOV/GREATFALLS