270 
FXUS65 KTFX 291206
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
505 AM MST MON NOV 29 2010

.DISCUSSION...

TODAY THROUGH WEDNESDAY...A BROAD UPPER LEVEL TROUGH WITH MOST 
DYNAMICS TO THE SOUTH AND EAST OF THE REGION...WILL MOVE TO THE
EAST AS AN UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS OVER MONTANA
OVER THE NEXT COUPLE OF DAYS. AREAS OF LIGHT SNOW CONTINUE TO
DIMINISH AS DRIER MOVES IN FROM THE NORTH WEST. THERE WILL BE ARES
OF FREEZING FOG ACROSS PARTS OF NORTH CENTRAL MONTANA THIS
MORNING. SKIES WILL BECOME PARTLY CLOUDY BY LATE MORNING WITH
UNSEASONABLY COOL WEATHER TODAY. BY TONIGHT...SOUTHWEST WINDS WILL
INCREASE AS A SURFACE TROUGH DEVELOPS ACROSS SOUTHERN
CANADA...EXTENDING INTO CENTRAL MONTANA. WINDS WILL BECOME STRONG
ON TUESDAY INTO TUESDAY NIGHT...RESULTING IN MODERATING
TEMPERATURES ALONG WITH AREAS OF BLOWING AND DRIFTING OF
SNOW...ESPECIALLY ACROSS PARTS OF NORTH CENTRAL MONTANA. SKIES
WILL ALSO BECOME MOSTLY CLOUDY WITH AREAS OF LIGHT SNOW ACROSS THE
ROCKY MOUNTAINS FRONT AS PACIFIC MOISTURE INCREASES IN A WEST TO
NORTHWEST FLOW. HAVE DECIDED NOT TO GO FOR A HIGH WIND WATCH AS
MAX WINDS ARE ONLY AROUND 50 KTS AT 800 MB OVER THE ROCKY MOUNTAIN
FRONT. BUT WILL STRONGLY MENTION STRONG WINDS IN FORECAST. ANOTHER
CONCERN IS BLOWING AND DRIFTING SNOW. HOWEVER...CURRENT REPORTS
WERE ONLY ABOUT AN INCH. WILLIAMSON DC

WEDNESDAY NIGHT THROUGH TUESDAY...CONFIDENCE IN THE FORECAST IS LOW 
WITH RESPECT TO THE CHANCES OF PRECIPITATION BUT CONFIDENCE IS HIGH 
THAT TEMPERATURES WILL GENERALLY BE BELOW NORMAL..ESPECIALLY FOR THE 
PLAINS. LATER THIS WEEK A WEATHER DISTURBANCE ALOFT IS FORECAST TO 
MOVE THROUGH THE FORECAST AREA BUT MODELS DIFFER GREATLY ON ITS 
TIMING. ALTHOUGH SNOW IS A GOOD BET WITH THE WEATHER 
DISTURBANCE..DUE TO THE BIG DIFFERENCES IN WHERE AND WHEN THE MODELS 
HAVE SNOW..HAVE KEPT THE THREAT OF SNOW IN ANY 12 HOUR PERIOD IN THE 
CHANCE CATEGORY. PREVIOUS RUN OF THE GFS MODEL HAD A CLOSED UPPER 
LOW MOVING SOUTH OVER THE AREA LATER IN THE WEEKEND WITH A SHOT OF 
SNOW AND VERY COLD TEMPERATURES. LATEST RUN OF THE GFS HAS BACKED 
OFF ON THIS IDEA AND IS MORE IN LINE WITH THE GEM MODEL WHICH HAS AN 
UPPER RIDGE APPROACHING THE AREA LATE IN THE WEEKEND. THE ECMWF 
MODEL IS SLOWER WITH THE UPPER RIDGE THAN THE GEM/GFS MODELS BUT ALL 
3 MODEL RUNS DO DEVELOP AN UPPER RIDGE OVER THE AREA BY TUESDAY. 
GOING WITH THE GEM/LATEST GFS SOLUTION..INHERITED FORECAST WHICH WAS 
DRY OVER THE PLAINS LATE IN THE WEEKEND SEEMS PLAUSIBLE AND WILL 
CONTINUE WITH THIS IDEA AND EXTEND IT THROUGH TUESDAY. INHERITED 
FORECAST DID HAVE A THREAT OF SNOW FOR THE WESTERN AND SOUTWWESTERN 
MOUNTAINS LATE IN THE WEEKEND. RIDGE MIGHT BE STRONG ENOUGH TO KEEP 
THESE AREAS DRY AS WELL BUT SINCE CONFIDENCE IS NOT HIGH WILL 
CONTINUE TO MENTION A THREAT OF SNOW. BLANK  

&&

.AVIATION...
UPDATED 1205Z.
EXPECT AREAS OF MVFR CEILINGS/VISIBILITIES AND LOCAL IFR 
CEILINGS/VISIBILITIES IN LIGHT SNOW AND FOG EARLY THIS MORNING. BY 
NOON CONDITIONS SHOULD BE VFR. BY LATE AFTERNOON CONDITIONS SHOULD 
NOT ONLY BE VFR BUT SKIES SHOULD BE CLEAR. TONIGHT CEILINGS ABOVE 
15000 FEET ARE EXPECTED TO SPREAD EAST OVER THE AREA. ALSO TONIGHT 
SOME GUIDANCE IS SUGGESTING THE THREAT OF IFR CEILINGS/VISIBILITIES 
IN FOG. THOUGHT THE THREAT WAS GREAT ENOUGH TO MENTION IN THE KHVR 
TAF BUT CONDITION CAN NOT BE RULED OUT AT KLWT/KBZN/KHLN. THERE 
SHOULD BE ENOUGH WIND TO PRECLUDE CONDITION AT KGTF AND KCTB. ALSO 
TONIGHT COULD SEE MVFR/IFR VISIBILITIES IN BLOWING SNOW OVER THE 
ROCKY MOUNTAIN FRONT. BLANK 

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  26  14  33  25 /  10   0   0  10 
CTB  25  14  32  24 /  10   0  10  10 
HLN  21   7  27  18 /  10   0  10  20 
BZN  20  -2  24  13 /  20   0   0  20 
WEY  16  -2  19   6 /  20  10  20  30 
DLN  18   1  25  15 /  20  10  10  30 
HVR  21   6  30  17 /  10   0   0  10 
LWT  23   7  30  21 /  20   0   0  10 

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...WILLIAMSON DC
LONG TERM...BLANK
AVIATION...BLANK

WEATHER.GOV/GREATFALLS