FXUS65 KTFX 290532
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1032 PM MST SAT NOV 28 2009
UPDATED AVIATION DISCUSSION
UPDATE...NARROW BAND OF CLOUDS WITH A FEW EMBEDDED LIGHT SNOWSHOWERS
MOVING NORTH TO SOUTH ALONG THE CONTINENTAL DIVIDE ARE THE ONLY
WEATHER ITEMS OF NOTE THIS EVENING. THAT BAND WILL CONTINUE TO MOVE
SOUTH AND WEAKEN TONIGHT RESULTING IN A PERIOD OF CLEAR TO PARTLY
CLOUDY SKIES OVERNIGHT FOR MOST OF CENTRAL AND SOUTHWEST MT. MADE
ONLY SLIGHT ADJUSTMENTS TO SHORT-TERM FORECAST GRIDS TO REDUCE POPS
OVER SOUTHWEST ZONES AND DECREASE OVERNIGHT LOW TEMPERATURES A FEW
DEGREES ACROSS THE REGION. REST OF FORECAST IS ON TRACK.
WARANAUSKAS
.DISCUSSION...
TONIGHT THROUGH MONDAY...HIGH PRESSURE RIDGE SITTING OVER PACIFIC
NORTHWEST COAST WITH MOISTURE SPILLING OVER TOP AND INTO NORTH
CENTRAL MONTANA. SOME VERY SMALL SYSTEMS EMBEDDED IN THIS FLOW
EXPECTED TO BE STRONG ENOUGH TO CREATE SOME SCATTERED SNOW SHOWERS
TONIGHT...MAINLY OVER THE MOUNTAINS. TEMPERATURES WILL AGAIN WARM
SUNDAY AND MONDAY AS SURFACE PRESSURE GRADIENTS GRADUALLY INCREASE
IN RESPONSE TO SURFACE LOW THAT WILL DEVELOP OVER ALBERTA. THE
RESULT WILL BE YET ANOTHER ROUND OF GUSTY WEST WINDS...ESPECIALLY
ALONG THE ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS. CURRENTLY...IT
APPEARS WINDS WILL BE CLOSE TO BUT BELOW WARNING CRITERIA AND NO
HIGHLIGHTS ARE EXPECTED AT THIS TIME. WILL LET LATER SHIFTS RE-
EVALUATE SITUATION AS NECESSARY. LITTLE IN THE WAY OF
PRECIPITATION EXPECTED SUNDAY AND MONDAY UNDER THE INFLUENCE OF
THE RIDGE AND WEST WINDS...THOUGH COULD SEE SOME SNOW SHOWERS OVER
THE MOUNTAINS.
MONDAY NIGHT THROUGH THURSDAY NIGHT...A CANADIAN COLD FRONT WILL
MOVE SOUTHWARD THROUGH THE REGION ON TUESDAY. EXPECT A RETURN TO
MORE WINTER/SEASONAL TEMPERATURES OVER THE REGION BEGINNING ON
TUESDAY AND THEN CONTINUING THROUGH THE REST OF THE WEEK. THERE
WILL BE A GOOD CHANCE FOR SNOW WITH THE FRONTAL PASSAGE...BUT
TOTAL SNOW ACCUMULATIONS ON TUESDAY STILL LOOK TO BE ON THE MINOR
SIDE...WITH AROUND OF INCH OF SNOWFALL EXPECTED AT LOWER
ELEVATIONS AND 2 TO 4 INCHES IN THE MOUNTAINS. FAIRLY QUIET
WEATHER IS EXPECTED FOR WEDNESDAY AND THURSDAY...WITH ANY
PRECIPITATION THAT FALLS CONFINED MAINLY TO MOUNTAINS...AND
TEMPERATURES RETURNING TO SLIGHTLY BELOW NORMAL READINGS. BRUSDA
FRIDAY THROUGH SATURDAY...MODEL DIFFERENCES AND RUN TO RUN
INCONSISTENCIES DETRACT FROM FORECAST CONFIDENCE DURING THIS PERIOD.
THIS FORECAST LEANS TOWARD THE ECMWF WHICH HAS SHOWN A LITTLE BETTER
RUN TO RUN CONTINUITY. A RIDGE OVER THE WEST COAST RESULTS IN A COLD
BUT GENERALLY DRY NORTHERLY FLOW ALOFT. A WEAK FRONT SLIDES SOUTH
EARLY FRIDAY...WITH WINDS SHIFTING NORTHERLY BEHIND THE FRONT AND
TEMPERATURES FALLING. NOT MUCH MOISTURE WITH THE FRONT SO ONLY A
CHANCE OF SNOW OVER THE MOUNTAINS IS EXPECTED. A WEAK UPPER LEVEL
SHORTWAVE MOVES QUICKLY SOUTHEAST ACROSS THE REGION FRIDAY NIGHT
WITH INCREASING CLOUDS...A CHANCE OF SNOW CONTINUES OVER THE
MOUNTAINS WITH A SLIGHT CHANCE OVER THE VALLEYS AND UPSLOPE AREAS OF
THE PLAINS. DRIER AIR ALOFT SATURDAY SHOULD BRING DECREASING CLOUDS
AND PRECIPITATION. TEMPERATURES WILL BE A LITTLE BELOW SEASONAL
AVERAGES. EK
&&
.AVIATION...
UPDATED 0600Z.
AN UPPER LEVEL RIDGE BUILDING EASTWARD INTO THE PACIFIC NW AND
NORTHERN ROCKIES WILL MAINTAIN A STABLE AND MOSTLY DRY NW FLOW ALOFT
ACROSS THE REGION THROUGH THE NEXT 24 HRS. A WEAK DISTURBANCE
EMBEDDED WITHIN THE NW FLOW WILL PRODUCE SOME VERY ISOLATED LIGHT
SNOW SHOWERS AND MTN OBSCURATIONS ALONG NORTHERN PORTIONS OF THE
CONTINENTAL DIVIDE TONIGHT...HOWEVER THE MAJORITY OF THE CENTRAL AND
SW MT WILL ONLY SEE A PERIOD OF THICKER MID TO HIGH CLOUDS WITH VFR
CONDITIONS PREVAILING. HOENISCH
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 30 49 34 55 / 0 0 0 0
CTB 27 48 31 52 / 0 0 0 0
HLN 24 47 28 49 / 10 10 10 0
BZN 13 39 15 44 / 10 10 10 10
WEY -1 33 11 32 / 10 10 10 0
DLN 18 38 19 43 / 0 10 10 10
HVR 20 52 28 56 / 0 0 0 0
LWT 21 48 29 53 / 10 10 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...LOSS
LONG TERM...BRUSDA/EK
AVIATION...HOENISCH
WEATHER.GOV/GREATFALLS
