FXUS65 KTFX 232354
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
454 PM MST WED DEC 23 2009
...UPDATE TO AVIATION...
.DISCUSSION...
TONIGHT THROUGH CHRISTMAS DAY...FAIRLY QUIET BUT COLD WEATHER
EXPECTED OVER THE REGION THROUGH CHRISTMAS. PRECIPITATION THIS
AFTERNOON IS COMING TO AN END OVER THE REGION...WITH ANY NEW SNOW
FALL MAINLY CONFINED TO THE MOUNTAINS...WITH SNOW ACCUMULATIONS
LESS THAN A QUARTER OF AN INCH. WITH CLEARING SKIES
TONIGHT...FORECASTED LOWS ARE A BIT COLDER THAN GUIDANCE...AS GOOD
RADIATIONAL COOLING SHOULD OCCUR AFTER MIDNIGHT.
ADDITIONALLY...PATCHY FREEZING FOG COULD ALSO DEVELOP...ESPECIALLY
OVER NORTH CENTRAL MONTANA. FOR THURSDAY...GENERALLY SEASONABLY
COLD CONDITIONS EXPECTED OVER THE REGION...BUT NO PRECIP IS
EXPECTED. EXPECT THE QUIET TREND TO CONTINUE INTO CHRISTMAS
DAY...WITH NO PRECIPITATION EXPECTED ACROSS THE REGION AT THIS
TIME. TEMPERATURES SHOULD MODERATE A BIT...BUT STILL REMAIN ABOUT
10 DEGREES BELOW NORMAL. BRUSDA
FRIDAY NIGHT THROUGH WEDNESDAY...LONG-RANGE MODELS IN FAIR AGREEMENT
REGARDING STRONG RIDGE OF HIGH PRESSURE BUILDING OVER THE WESTERN
U.S. DURING THE START OF THE FORECAST PERIOD. NORTHERLY FLOW AND
SNOWPACK WILL KEEP TEMPERATURES IN CHECK WITH HIGH TEMPERATURES
AROUND SEASONAL AVERAGES SATURDAY AND SUNDAY. DRY CONDITIONS ARE
ALSO EXPECTED. THERE ARE SOME MODEL DIFFERENCES REGARDING THE
PLACEMENT OF THE HIGH ALOFT AS THE ECMWF ATTEMPTS TO BRING IN A
WEAK UPPER-LEVEL LOW ONTO THE WEST COAST ON SUNDAY WHICH WILL KEEP
THE CENTER OF THE HIGH OVER SOUTHERN ALBERTA RATHER THAN MONTANA
AS THE GFS INDICATES. NEVERTHELESS...DRY CONDITIONS ARE EXPECTED
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. MODELS CONTINUE TO
SHOW CONSIDERABLE DIFFERENCES WITH REGARDS TO OUR NEXT PRECIP
CHANCES...HOWEVER BOTH THE GFS AND EC HINT AT A TROUGH OF LOW
PRESSURE MOVING INTO THE PACIFIC NORTHWEST TUESDAY AND WEDNESDAY
OF NEXT WEEK. A COLDER CANADIAN AIRMASS MAY ALSO SLIDE INTO THE
AREA DURING THIS SAME TIME FRAME SO TRENDED TEMPERATURES ABOUT 5
TO 10 DEGREES BELOW AVERAGE. MLS
&&
.AVIATION...
UPDATED 2354Z.
VFR CONDITIONS WILL DOMINATE OVER THE NEXT 24 HOUR PERIOD...HOWEVER
ALL TAF SITES DO HAVE A SMALL CHANCE OF FOG FORMING DURING THE
OVERNIGHT HOURS. WILL CONTINUE TO MONITOR TEMPERATURES AS THE
SUNSETS UNDER CLEARING SKIES. TEMPERATURES ARE ALREADY DROPPING
SIGNIFICANTLY AND WITH FRESH SNOWFALL SOME RADIATIONAL FOG COULD
FORM. MODELS ARE CURRENTLY SHOWING ENOUGH OF A DRAINAGE WIND AT
SITES ACROSS THE AREA THAT FOG OR EVEN LOW STRATUS WOULD BE
INHIBITED. CURRENTLY THE LIKELIHOOD OF FOG FORMATION IS LOW ENOUGH
TO AVOID MENTIONING IN THE CURRENT SET OF TAFS. IF CONDITIONS CHANGE
AMENDMENTS WILL BE ISSUED. SUK
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF -14 12 -8 23 / 0 0 0 0
CTB -20 11 -9 28 / 0 0 0 0
HLN -11 9 -5 17 / 0 0 0 0
BZN -15 8 -12 16 / 10 0 0 0
WEY -15 13 -12 17 / 30 10 10 10
DLN -2 14 1 21 / 10 0 0 0
HVR -25 -3 -17 13 / 0 0 0 0
LWT -13 7 -10 22 / 10 0 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
