FXUS65 KTFX 091806
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 AM MST WED DEC 9 2009
.UPDATE...
TODAY...AN UPPER LEVEL DISTURBANCE IS MOVING SOUTH THROUGH THE FLOW
ALOFT. ASSOCIATED WITH THIS WILL BE A PUSH OF CANADIAN AIR ACROSS
THE BORDER AND SOME ADDITIONAL LOW LEVEL MOISTURE. STRONG WEST
WINDS WILL HELP KEEP ZONES IN THE LEE OF THE ROCKIES DRY BUT
POINTS FARTHER EAST WILL HAVE A CHANCE OF LIGHT SNOW. BRISK WINDS
WILL INCREASE DURING THE DAY BUT TEMPERATURES WILL BE RISING SO
WINDS CHILLS WILL RISE ABOVE NEGATIVE 20. WILL LET THE WIND CHILL
ADVISORY EXPIRE. ZELZER
&&
.AVIATION...
UPDATED 1800Z.
NORTHWEST FLOW ALOFT WILL CONTINUE OVER THE AREA. THE AIRMASS WILL
REMAIN SOMEWHAT UNSTABLE WITH SCATTERED SNOW SHOWERS OVER THE
MOUNTAINS AND ISOLATED SNOW SHOWERS OVER THE PLAINS. WEST SURFACE
WINDS WILL BECOME BREEZY MID-DAY. VFR CONDITIONS WILL PREVAIL FOR
THE MOST PART WITH MVFR CONDITIONS POSSIBLE AT A FEW SITES AND IN
THE VICINITY OF SNOW SHOWERS. MOUNTAINS MAY BE OBSCURED AT TIMES.
&&
.PREV DISCUSSION...
/ISSUED 440 AM MST WED DEC 9 2009/
TODAY THROUGH FRIDAY...WEST TO SOUTHWEST WINDS HAVE DEVELOPED OVER
WESTERN PORTIONS OF THE NORTH CENTRAL MT PLAINS IN RESPONSE TO
A MORE NORTHWESTERLY FLOW ALOFT AND SHORTWAVE ENERGY EMBEDDED
WITHIN THAT FLOW. THIS HAS BEGUN THE PROCESS OF SWEEPING OUT THE
VERY COLD ARCTIC AIRMASS WITH TEMPERATURES RISING THROUGH THE
NIGHT OVER WESTERN PORTIONS OF THE PLAINS AND SOME LOCATIONS ALONG
THE EAST SLOPES OF THE ROCKIES HAVE ALREADY RISEN ABOVE ZERO. MOST
LOCATIONS SHOULD SEE TEMPERATURES RISE ABOVE ZERO TODAY AS THE3
ARCTIC AIRMASS IS SWEPT OUT OR AT LEAST GRADUALLY MODIFIED WITH
THE MOST PRONOUNCED WARMING OVER WESTERN PORTIONS OF NORTH
CENTRAL MT AND THE LEAST/SLOWEST WARMING OVER THE SW MT VALLEYS
AND FAR NE ZONES. DESPITE THE WARMING TEMPS...BREEZY WEST WINDS WILL
ALSO SPREAD EAST OVER MUCH OF NORTH CENTRAL MT TODAY...MAKING
CONDITIONS FEEL MUCH COLDER. WIND CHILL VALUES WILL LIKELY REMAIN
BELOW -20 FOR THROUGH EARLY THIS MORNING AND A WIND CHILL ADVISORY
WILL REMAIN IN EFFECT THROUGH 9AM THIS MORNING. NOT AS COLD
TONIGHT...BUT TEMPS WILL LIKELY STILL FALL BELOW ZERO FOR MOST OF
THE FORECAST AREA...ESPECIALLY SW MT. ADDITIONAL WARMING OCCURS
THURSDAY AND FRIDAY BUT TEMPS WILL REMAIN BELOW AVERAGE. CYCLONIC
NW FLOW ALOFT PERSISTS OVER THE REGION THROUGH FRIDAY AND WHILE
MOISTURE IS VERY LIMITED...A FEW SNOW SHOWERS MAY OCCUR AT
TIMES...ESPECIALLY OVER THE MTNS. ANY ACCUMULATIONS WOULD BE VERY
LIGHT AND MAINLY LIMITED TO THE MTNS.
FRIDAY NIGHT THROUGH WEDNESDAY...MEDIUM RANGE MODELS SHOWING A BIT
MORE CONSISTENCY DURING THE PERIOD. AN UPPER LOW OVER SOUTHERN
CANADA FRIDAY NIGHT STEERS THE FLOW ALOFT TO A MORE WESTERLY
DIRECTION. MOISTURE WITH THIS FEATURE THEN MERGES WITH MOISTURE THAT
MOVES UP FROM THE SOUTHWEST UNITED STATES AND BRINGS A CHANCE OF
SNOW TO THE NORTHERN PORTION OF THE COUNTY WARNING AREA. SCATTERED
SNOW CONTINUES THROUGH SUNDAY AS IMPULSES OF SHORT WAVE ENERGY
CONTINUE TO ROTATE ACROSS THE AREA. BOTH THE EUROPEAN AND GFS MODELS
PUSH A BACKDOOR COLD FRONT ACROSS THE AREA ON SUNDAY NIGHT INTO
MONDAY. HAVE DROPPED MONDAY AFTERNOON HIGH TEMPERATURES CONSIDERABLY
ACROSS THE NORTH AND PORTIONS OF CENTRAL MONTANA AS THIS SURGE OF
COLD AIR PUSHES AS FAR SOUTH AND WEST AS GREAT FALLS. MODELS BEGIN
TO DIVERGE IN THEIR SOLUTIONS BY MIDWEEK WITH THE EUROPEAN MOVING
THE COLD AIR OUT MUCH FASTER THAN THE GFS. HAVE GONE WITH A SLOWER
MODERATING TREND WITH TEMPERATURES AND A CONTINUED SLIGHT CHANCE OF
SNOW ACROSS SOUTHWEST AND CENTRAL MONTANA. TEMPERATURES WILL REMAIN
BELOW SEASONAL AVERAGES.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 10 -3 14 1 / 20 10 20 10
CTB 10 -1 13 1 / 20 10 20 10
HLN 4 -10 10 -3 / 20 10 20 10
BZN 2 -16 10 -9 / 30 20 20 10
WEY 1 -19 6 -12 / 40 30 30 20
DLN 5 -14 12 -5 / 20 10 10 10
HVR 6 -11 11 -10 / 30 20 20 10
LWT 5 -6 11 -1 / 30 30 20 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
