FXUS65 KTFX 102207
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
307 PM MST THU DEC 10 2009
.DISCUSSION...
TONIGHT THROUGH SATURDAY...THE ZONES ARE UNDERNEATH NORTHWEST FLOW
ALOFT WHICH IS ASSOCIATED WITH A LOW PRESSURE SYSTEM IN CANADA.
WESTERLY FLOW TO THE SOUTH OF THE ZONES IS ASSOCIATED WITH A
SHORTWAVE OVER THE PACIFIC. HIGH PRESSURE ALOFT WILL CONTINUE TO
BUILD OVER THE REGION AND SEVERAL DISTURBANCES WILL MOVE THROUGH THE
NORTHWEST FLOW ALOFT. THE UPPER LEVEL FLOW GRADUALLY SHIFTS TO THE
WEST THROUGH THE PERIOD AND MID LEVEL WINDS REMAIN STRONG. LIGHT
SNOW ASSOCIATED WITH THE CURRENT UPPER LEVEL DISTURBANCE WILL AFFECT
MOSTLY THE SOUTHWEST ZONES DURING THE EVENING. THE CHANCE FOR PRECIP
WILL REMAIN SLIGHT FRIDAY BUT THE CHANCE BEGINS TO INCREASE LATE
FRIDAY AS A BOUNDARY SETS UP ACROSS THE HILINE. A SECOND SOURCE OF
PRECIP WILL MOVE UP TOWARDS THE SOUTHWEST THAT IS ASSOCIATED WITH
THE PACIFIC SHORTWAVE. HIGHEST CHANCE OF PRECIP WILL BE OVER THE
EXTREME SOUTHERN MOUNTAINS WHERE SNOW SHOULD BE ACCUMULATING BY
SATURDAY. TEMPS WILL REMAIN AT OR BELOW SEASONAL NORMALS BUT BEGIN
TO APPROACH NORMALS BY SATURDAY. ZELZER
SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODELS CONTINUE TO
EXHIBIT GENERAL SIMILARITIES DURING THE PERIOD. A CLOSED UPPER LOW
OVER CENTRAL CANADA WILL PUSH A LARGE AREA OF MOISTURE SOUTH ACROSS
THE CANADIAN BORDER ON SUNDAY MERGING WITH MOISTURE WORKING ITS WAY
NORTH FROM THE SOUTHWEST US. THE RESULT WILL BE ACCUMULATING
SNOWFALL OVER THE ROCKY MOUNTAIN FRONT AND SCATTERED SNOW OVER MOST
OF THE REST OF COUNTY WARNING AREA. A SURFACE COLD FRONT WILL MOVE
ACROSS THE AREA SUNDAY BRINGING MUCH COLDER AIR AS FAR SOUTH AS
GREAT FALLS WHILE ONLY COOLING SOUTHWEST MONTANA A BIT. SCATTERED
SNOW AND COLD TEMPS WILL CONTINUE MONDAY AS THE AREA REMAINS UNDER
NORTHWEST FLOW ALOFT. THE REMAINDER OF THE PERIOD WILL SEE A DRYING
AND WARMING TREND AS A WEAK UPPER RIDGE MOVES ACROSS THE CONTINENTAL
DIVIDE BY THURSDAY. ISOLATED SNOW SHOWERS WILL REMAIN A POSSIBILITY
FOR THE WESTERN MOUNTAINS AS WELL AS THE MOUNTAINS OF SOUTHWEST
MONTANA. TEMPS WILL REMAIN BELOW SEASONAL AVERAGES UNTIL THE MIDDLE
OF NEXT WEEK WHEN IT APPEARS A STRONGER WARMING TREND MAY BEGIN.
&&
.AVIATION...
UPDATED 1800Z.
NORTHWEST FLOW ALOFT WILL PERSIST. BREEZY SURFACE WINDS WILL
CONTINUE ALONG THE ROCKY MOUNTAIN FRONT AS WELL AS OVER THE PLAINS.
WINDS WILL SLOWLY DIMINISH THIS AFTERNOON. THERE IS ENOUGH
INSTABILITY WITHIN THE NORTHWEST FLOW ALOFT FOR ISOLATED SNOW
SHOWERS BUT THESE WILL OCCUR MAINLY OVER HIGHER TERRAIN. VFR
CONDITIONS WILL PREVAIL WITH MVFR CONDITIONS IN THE VICINITY OF
SNOW SHOWERS AS WELL AS OCCASIONAL MOUNTAIN OBSCUREMENT.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 9 29 16 31 / 10 10 10 20
CTB 6 24 8 24 / 10 10 30 30
HLN 4 24 8 28 / 10 10 10 20
BZN -3 22 2 30 / 10 10 20 30
WEY -10 17 3 24 / 10 10 60 60
DLN -1 23 7 30 / 10 10 20 30
HVR 1 22 4 22 / 10 10 30 20
LWT 1 27 6 29 / 10 10 10 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
