FXUS65 KTFX 231747
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1050 AM MST WED DEC 23 2009
.UPDATE...
LIGHT SNOW CONTINUES TO FALL OVER MUCH OF NORTH CENTRAL MONTANA
THIS MORNING. OVERALL...REPORTED SNOWFALL GENERALLY RANGE FROM 2
TO 4 INCHES...WITH ISOLATED 5 INCH REPORTS. THE SNOW SHOULD
CONTINUE THROUGH THE MORNING...BEFORE GRADUALLY TAPERING OFF FROM
WEST TO EAST THIS AFTERNOON. NEW SNOW AMOUNTS WILL GENERALLY RANGE
FROM 1 TO 2 INCHES TODAY. COLDER AIR CONTINUES TO WORK ITS WAY
SOUTHWARD INTO THE REGION. TEMPERATURES WILL GENERALLY HOLD STEADY
OR SLIGHTLY FALL OVER NORTH CENTRAL MONTANA. NOT MUCH OF A
TEMPERATURE RISE IS EXPECTED OVER SOUTHWEST MONTANA. FOR
TONIGHT...WITH CLEARING SKIES...IT COULD BE VERY COLD OVER NORTH
CENTRAL MONTANA. TEMPERATURES COULD BE LOWERED A BIT TO THE 10 TO
15 BELOW RANGE OVER NORTH CENTRAL MONTANA. THIS WILL BE LOOKED AT
CLOSER LATER TODAY. OTHERWISE...FAIRLY QUIET AND SEASONABLE
DECEMBER WEATHER IS EXPECTED TONIGHT THROUGH CHRISTMAS. BRUSDA
&&
.AVIATION...
UPDATED 1750Z.
HAVE HIGH CONFIDENCE IN IMPROVING WEATHER CONDITIONS DURING THE TAF
PERIOD. FAIRLY WIDESPREAD MVFR AND EVEN IFR CEILINGS AND VISIBILTIES
AND AREAS OF SNOW WILL DIMINISH DURING THE AFTERNOON. ALONG WITH
THIS TREND MOUNTAIN OBSCUREMENT WILL ALSO BECOME LESS WIDESPREAD
THROUGH THE AFTERNOON. AFTER 00Z EXPECT VFR CONDITIONS WITH THE
POSSIBILITY OF SOME LINGERING MVFR/IFR CONDITIONS IN SNOW SHOWERS
OVER SOUTHWEST MONTANA THROUGH 03Z. DURING THE 03Z-12Z PERIOD AM
CONFIDENT THAT SKIES WILL CLEAR. DO NOT SEE MUCH THREAT FOR FREEZING
FOG LATE TONIGHT/THURSDAY MORNING SO HAVE NOT MENTIONED IT IN THE
TAFS. WINDS SHOULD GENERALLY BE LESS THAN 10 KNOTS BUT CONFIDENCE IN
FORECAST WINDS DIRECTIONS IS ONLY FAIR. BLANK
&&
.PREV DISCUSSION...
/ISSUED 508 AM MST WED DEC 23 2009/
TODAY THROUGH FRIDAY...A LOW PRESSURE TROF WILL QUICKLY MOVE FROM
CENTRAL MONTANA INTO EASTERN MONTANA TODAY WHILE A HIGH PRESSURE
RIDGE OVER THE EASTERN PACIFIC BUILDS OVER THE WEST COAST. THIS WILL
PUT THE ZONES UNDERNEATH NORTH FLOW ALOFT AND KEEP THE REGION UNDER
A COLD AIRMASS. SNOW WILL QUICKLY TAPER OFF AS THE TROF MOVES EAST
ALTHOUGH NORTHERLY FLOW WILL CONTINUE TO KEEP A THREAT OF SNOW
SHOWERS IN THE AREA. CURRENT ADVISORIES WILL BE CONTINUED. BUILDING
HIGH PRESSURE WILL DOMINATE THE REMAINING PERIOD...THE AIRMASS WILL
STAY DRY AND SLOWLY WARM. TEMPS WILL REMAIN BELOW NORMALS THROUGH
THE PERIOD ALTHOUGH TRENDING WARMER THROUGH FRIDAY. ZELZER
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
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 7 -2 15 1 / 100 10 0 0
CTB 5 -8 15 0 / 40 0 0 0
HLN 14 -1 12 -3 / 100 10 0 0
BZN 25 -3 16 -10 / 90 10 0 0
WEY 23 -10 13 -10 / 70 20 10 0
DLN 26 -3 17 -7 / 30 10 0 0
HVR 7 -17 0 -12 / 100 10 0 0
LWT 9 -6 12 -4 / 100 10 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING FOR
CASCADE...CHOUTEAU...EASTERN GLACIER...EASTERN PONDERA...EASTERN
TETON...HILL...JUDITH BASIN...LIBERTY...MEAGHER...NORTHERN ROCKY
MOUNTAIN FRONT...SOUTHERN ROCKY MOUNTAIN FRONT...TOOLE.
WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
BLAINE...FERGUS.
&&
$$
WEATHER.GOV/GREATFALLS
