FXUS65 KTFX 010426
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
910 PM MST MON NOV 30 2009
UPDATE...THE EXPECTED COLD FRONT IS CURRENTLY PASSING THRU CENTRAL
MONTANA AND WILL CONTINUE TO MAKE STEADY SOUTHWARD PROGRESS
OVERNIGHT. WITH THE PRESSURE GRADIENT DECREASING BEHIND THE
FRONT...WINDS ACROSS THE ROCKY MTN FRONT AND ADJACENT PLAINS HAVE
BEGUN TO WEAKEN AND WILL CONTINUE TO DO SO TONIGHT. SO HAVE
CANCELLED THE HIGH WIND WARNING FOR THOSE NORTHWEST ZONES.
POST-FRONTAL AREAS OF LIGHT SNOW HAVE DEVELOPED OVER
GLACIER-TETON-PONDERA COUNTIES AND THIS SNOW IS EXPECTED TO SPREAD
TO THE SOUTH AND EAST OVERNIGHT. MOISTURE AVAILABLE FOR SNOW
REMAINS LOW SO ONLY LIGHT ACCUMULATIONS ARE FORECAST...GENERALLY AN
INCH OR LESS FOR LOW ELEVATIONS FROM GREAT FALLS SOUTHWARD AND 2 TO
3 INCHES IN THE MOUNTAINS. TEMPS WILL BE CHILLY TOMORROW WITH HIGHS
ONLY IN THE MID 20S TO LOW 30S. WARANAUSKAS
.DISCUSSION...
TONIGHT THROUGH WEDNESDAY...A SHORTWAVE WILL MOVE OVER THE
ROCKIES TONIGHT WITH A COLDER NORTHERLY FLOW FOLLOWING DURING THE
DAY TOMORROW. EXPECT STRONG WINDS TO CONTINUE THROUGH THE EVENING
ACROSS MUCH OF THE REGION. THE CURRENT WIND WARNING WILL THUS
CONTINUE AND EXPIRES AT MIDNIGHT TONIGHT. SNOW ACCUMULATIONS WITH
THE SHORTWAVE WILL NOT BE ANYTHING OF NOTE. THE MOUNTAINS MAY GET
A FEW INCHES BUT GENERALLY ONLY AN INCH OR SO IS EXPECTED IN MOST
LOWER ELEVATIONS. THE MAIN AREA OF MOISTURE SHOULD CROSS THE
CANADIAN BORDER AFTER 00Z TUE AND ACROSS KCTB AND KHVR BY 09Z.
MOISTURE JUMPS QUICKLY INTO THE CENTRAL ZONES DURING THE MORNING.
SNOW WILL WEAKEN BY LATE TUESDAY MORNING AND SHOULD BE CONFINED TO
THE SOUTH CENTRAL PORTION OF THE STATE BY AFTERNOON. THE AIRMASS
WILL COOL QUICKLY BEHIND THE FRONT. COLD AIR CONTINUES TO MOVE
INTO THE AREA THROUGH TUESDAY NIGHT. THE AIRMASS DRIES WEDNESDAY
BUT WITH A FRESH COATING OF SNOW AND CLEARING SKIES AS WELL AS
COLDER NORTHERLY FLOW...TEMP RECOVERY WILL BE DIFFICULT. EXPECT
OVERNIGHT LOWS TO BE MUCH COLDER THAN THEY HAVE BEEN RECENTLY WITH
TEENS AND SINGLE DIGITS WEDNESDAY NIGHT AND BEYOND.
WEDNESDAY NIGHT THROUGH SATURDAY NIGHT...EXPECT A SEASONABLY COLD
AND DRY PERIOD OF WEATHER TO BEGIN THE PERIOD...AS A NORTHERLY FLOW
ALOFT RESIDES OVER THE REGION. TEMPERATURES WILL RANGE FROM 4 TO 8
DEGREES BELOW NORMAL THURSDAY...THEN MODERATE A FEW DEGREES FOR
FRIDAY...BEFORE COOLING OFF AGAIN ON SATURDAY. OVERALL...I WENT WITH
THE ECMWF MODEL...WHICH IS DRIER AND WARMER THROUGH SATURDAY. THE
GFS MODEL CONTINUES TO PROG MUCH COLDER AIR...AND PERIODS OF
SNOW...TO MOVE INTO THE REGION AS EARLY AS FRIDAY...BUT SINCE THE
GFS HAS SHOWN A TREND TO GO SLOWER WITH THIS COLD AIR MASS...I WENT
WITH THE ECMWF OVERALL...THUS THE MILDER/DRIER WEATHER PATTERN.
HOWEVER...THIS SITUATION WILL NEED TO BE WATCHED CLOSELY OVER THE
NEXT FEW DAYS...AS TEMPERATURES COULD BE OVER 20 DEGREES COLDER THAN
CURRENTLY FORECASTED SHOULD THE GFS PAN OUT...ALONG WITH A MUCH
BETTER CHANCE FOR SNOW. BRUSDA
SUNDAY THROUGH MONDAY...MODEL DIFFERENCES LESS SIGNIFICANT ON THIS
RUN...WITH BOTH ECMWF AND GFS INDICATING A DRAMATIC CHANGE TO WINTER
LIKE CONDITIONS. NORTHERLY SURFACE WINDS...PLUNGING TEMPERATURES AND
A CHANCE OF SNOW IS INDICATED. DUE TO SOME UNCERTAINTY PRECIPITATION
PROBABILITIES ARE KEPT NEAR CLIMO VALUES. MONDAY...LIGHTER UP-SLOPE
WINDS AND DRIER AIR ALOFT SHOULD RESULT IN SNOW TAPERING OFF OVER
THE NORTH. DAYTIME TEMPERATURES WILL FALL INTO THE TEENS TO NEAR 20
WITH LOWS IN SINGLE DIGITS ABOVE OR BELOW ZERO. EK
&&
.AVIATION...
UPDATED 0000Z.
AN UPPER LEVEL TROUGH CONTINUES TO DIG SE INTO THE REGION WHILE
SURFACE LOW PRESSURE TRACKS EAST ACROSS THE CANADIAN BORDER TONIGHT.
A COLD FRONT WILL DROP SOUTH ACROSS THE CANADIAN BORDER EARLY THIS
EVENING...REACHING CENTRAL MT BY AROUND 06Z AND CONTINUING SOUTH
THROUGH THE REMAINDER OF SW MT BY 12Z TUES. STRONG AND GUSTY WEST TO
SOUTHWEST WINDS AHEAD OF THE FRONT WILL SHIFT TO THE NW AND N BEHIND
THE FRONT AND DIMINISH SOMEWHAT BUT REMAIN BREEZY. CEILINGS WILL
LOWER TO MVFR BEHIND THE COLD FRONT WITH A PERIOD OF SNOW DEVELOPING
ABOUT 2 HRS AFTER THE FRONTAL PASSAGE. OCCASIONAL IFR CIGS/VIS WILL
BE POSSIBLE DURING PERIODS OF MORE INTENSE SNOWFALL. SNOW SHOULD
ONLY LAST FOR A PERIOD OF 2-4 HRS AT MOST TERMINALS WITH
ACCUMULATIONS GENERALLY AN INCH OR LESS. BREEZY N-NW WINDS WILL
PERSIST ON TUESDAY WITH GRADUAL IMPROVEMENT TO CIGS THROUGH LATE
MORNING WITH CLEARING FROM NORTH TO SOUTH BY TUESDAY AFTERNOON.
HOENISCH
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 29 7 27 / 60 80 0 0
CTB 23 28 6 28 / 60 70 0 0
HLN 29 33 16 29 / 40 70 10 0
BZN 26 28 -6 24 / 40 70 10 0
WEY 16 26 0 22 / 10 50 10 10
DLN 22 28 7 26 / 20 50 10 0
HVR 25 31 6 28 / 40 40 0 0
LWT 22 25 4 24 / 50 70 10 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL MIDNIGHT MST TONIGHT FOR MTZ009-010-044-
046-048-049.
&&
$$
SHORT TERM...GUSTAFSON
LONG TERM...COULSTON
AVIATION...HOENISCH
WEATHER.GOV/GREATFALLS
