000
FXUS65 KGGW 032144
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
244 PM MST WED DEC 3 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
GUSTY NORTHWEST WINDS AND ISOLATED FLURRIES ARE BEING DRIVEN BY
LOW LEVEL INSTABILITY ACROSS MUCH OF EASTERN MONTANA. EXPECT THE
BULK OF THE SHOWER ACTIVITY ALONG WITH THE GUSTY WINDS TO TAPER OFF
WITHIN A FEW HOURS OF SUNSET AS THE LOSS OF SOLAR GAIN WILL ALLOW
THE ATMOSPHERE TO STABILIZE. THE CURRENT LAKE WIND ADVISORY LOOKS
ON TRACK FOR NOW...ALTHOUGH MARGINAL CRITERIA WINDS MAY CONTINUE
FOR AN HOUR OR TWO AFTER IT EXPIRES. LATE TONIGHT THE CENTER OF
THE POLAR SURFACE HIGH WILL MOVE INTO THE CENTRAL PART OF THE
STATE. THIS WILL ALLOW FOR AT LEAST SOME PARTIAL CLEARING ACROSS
THE SOUTHWEST ZONES. THURSDAY THE SURFACE HIGH WILL REMAIN THE
DOMINANT FEATURE...CONTINUING TO DECREASE CLOUD COVER.
ALTHOUGH EVEN WITH CLEARING SKIES TEMPERATURES WILL CONTINUE TO
BE SOME 10 DEGREES BELOW NORMAL. THURSDAY NIGHT THE SURFACE HIGH
WILL SLIDE TO THE SOUTHEAST AS A LEE SIDE TROUGH DEVELOP WHILE A
CLIPPER CYCLONE SPINS UP OVER CENTRAL ALBERTA. EXPECT MID AND
HIGH LEVEL CLOUDS TO PICK UP AHEAD OF THIS SYSTEM. SAID LEE TROUGH
WILL SERVE TO WARM THE ATMOSPHERE...ALTHOUGH THE POLAR AIR IN
PLACE ACROSS THE EASTERN PART OF THE STATE WILL BE TOUGH TO SCOUR
OUT. FRIDAY THE CLIPPER SYSTEM WILL DROP TO THE SOUTH AND EAST.
THERE ARE MODEL DIFFERENCES ON THE EXACT TIMING OF THE
SYSTEM...THUS CONTINUED TO HOLD ON TO A 12 HOUR POP GRID.
TEMPERATURES WILL ALSO WARM AS THE POLAR IS SCOURED OUT...BUT KEPT
TEMPS BELOW GUIDANCE AS AN AIRMASS WILL BE VERY STABLE AND
STUBBORN TO MOVE OUT. GILCHRIST
.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...
FRIDAY NIGHT THROUGH SATURDAY NIGHT... TEMPERATURES ARE EXPECTED
TO REBOUND SLIGHTLY AS 850 MB TEMPS RISE SLOWLY FROM -8*C TO -4*C.
MODERATING OUT THIS REBOUND FOR SURFACE TEMPERATURES WILL BE
CLIPPER SYSTEM EMBEDDED IN THE NORTHWEST FLOW ALOFT. THIS SYSTEM
MAY BRING UP TO AND INCH OF SNOW FOR SOME AREAS AND MOSTLY CLOUDY
SKIES WELL ACROSS OUR CWA.
SUNDAY INTO MONDAY NIGHT... A PACIFIC NORTHWEST SHORTWAVE IS
EXPECTED TO PASS INTO THE THROUGH THE AREA. THIS SHORTWAVE SHOULD
AGAIN BRING A CHANCE FOR SNOW INTO THE FORECAST ALONG WITH COLD
AIR AND WINDY CONDITIONS DIRECTLY BEHIND IT. WHILE THE EXACT
TIMING AND STRENGTH FOR THIS SYSTEM AND ITS ASSOCIATED COLD AIR
AND WINDS IS IN QUESTION DUE TO THE PROGRESSIVE NATURE OF THE
CURRENT LONG TERM FORECAST... WINDS DURING THE EVENT CAN BE
EXPECTED TO REACH ROUGHLY 15 TO 25 MPH SUSTAINED WITH GUSTS UP TO
35 MPH POSSIBLE. WHILE THE BULK OF THIS SYSTEM WILL PASS THROUGH
IN ROUGHLY A DAY... DIRECTLY BEHIND IT EXISTS A CURIOUS FEATURE IN
THE MODELS THAT LOOKS TO BE A MINI SHORTWAVE ON MONDAY AND MONDAY
NIGHT. THE MINI SHORTWAVE SEEMS VERY SIMILAR TO THE CONDITIONS
THAT CREATED SMALL AMOUNTS OF SNOW FOR TODAY... THEREFORE POPS
WERE KEPT UP SLIGHTLY DURING THE PERIOD TO REFLECT THIS FEATURE.
TUESDAY INTO WEDNESDAY NIGHT... BRIEF WARMING AND COOL DOWN IS
AGAIN POSSIBLE WITH CLEARING SKIES AND 850 TEMPS RISING TO ROUGHLY
0*C TO 4*C THEN FALLING TO AROUND -12*C. WHILE THESE FEATURES ARE
EXPECTED... THE GFS AND ECMWF ARE SLIGHTLY DIFFERENT IN THE STRENGTH
OF THE EVENTS WITH THE GFS TAKING THE MORE AMPLIFIED ROUTE OF HOT
AND COLD AND THE ECMWF MODERATING THE SEVERITY OF THE SITUATION.
WITH CONFIDENCE BEING FAIR TO SLIGHTLY BELOW NORMAL THIS FAR OUT
THE MODERATED APPROACH SEEMS MORE LIKELY FOR NOW. HICKS
PREVIOUS LONG TERM DISCUSSION...
MUCH OF THE EXTENDED PERIOD WILL SEE AN AMPLIFIED LONG WAVE
PATTERN OVER THE NATION WITH A RIDGE TO THE WEST AND A TROUGH TO
THE EAST. THE PERIOD WILL BE ACTIVE WITH A PROGRESSIVE PATTERN OF
SEVERAL SHORT WAVES BRINGING UNSETTLED WEATHER TO THE LOCAL
REGION. IT BEGINS FRIDAY NIGHT WITH THE AREA UNDER A STRONG 100KT
PLUS NW JET ALOFT...MARKING THE BOUNDARY BETWEEN THE VERY COLD
ARCTIC AIR MASS AND LOW ANCHORED OVER HUDSON BAY AND A WARM WEST
COAST UPPER LEVEL HIGH CENTERED OFF SOUTHERN/BAJA CALIFORNIA. A
WEAK UPPER LEVEL DISTURBANCE/ENHANCED VORTICITY SHORTWAVE WILL BE
ABLE TO WRING OUT SOME MOISTURE IN THE FORM OF LOW QPF LIGHT SNOW
SHOWER/FLURRY ACTIVITY...MAINLY OVER NE ZONES. AS THE STATIONARY
BOUNDARY NUDGES EAST...OVERRUNNING MOISTURE AND WEAK UPPER LEVEL
DISTURBANCES WILL GENERATE ADDITIONAL SNOW SHOWERS SATURDAY AND
SATURDAY NIGHT...WITH SOME AFTERNOON RAIN POSSIBLY MIXED IN OVER
THE SOUTHWEST ZONES. THEN A MORE VIGOROUS SHORTWAVE LOW CROSSES
THE WASHINGTON/BRITISH COLUMBIA COAST SUNDAY MORNING WHICH WILL
INCREASE IN STRENGTH AS IT HEADS EAST AND DEVELOPS INTO AN COMPACT
CYCLONIC STORM SYSTEM EAST OF MT. THIS WAVE WILL PASS OVER THE
LOCAL AREA LATE SUNDAY THROUGH MONDAY WITH A SLIGHT CHANCE TO
CHANCE OF SNOW. BUT THE INVERTED TROUGH HEAD WILL REMAIN NORTH OF
THE LOCAL AREA KEEPING THE BEST CONDITIONS FOR HEAVIER
PRECIPITATION IN CANADA UNTIL THE STORM REACHES THE DAKOTAS. THERE
APPEARS TO BE A BRIEF REPRIEVE MONDAY NIGHT AND EARLY TUESDAY
BEFORE THE AREA IS AGAIN POSSIBLY CLOBBERED BY ANOTHER EASTERN
PACIFIC SHORTWAVE TROUGH LATE TUESDAY.
THERE SEEMS TO BE GENERAL AGREEMENT AMONG THE GFS/GEM/DGEX AND
ECMWF OPERATIONAL MODELS WITHOUT TOO MUCH SPREAD IN THE
ENSEMBLES. FORECASTER CONFIDENCE BEGINS GOOD...THEN BECOMES FAIR
BY EARLY NEXT WEEK AS TIMING AND LOCATION ISSUES BEGIN TO
APPEAR. SCT
TUESDAY THROUGH THURSDAY MORNING...LONG RANGE MODELS CONTINUE TO
LEAN TOWARD A PROGRESSIVE PATTERN WITH NORTHWEST FLOW NEXT WEEK.
HOWEVER...INCONSISTENCIES LIE WITH INTENSITY OF THE SHORTWAVE AND
THE AMOUNT OF MOISTURE ASSOCIATED WITH IT. BOTH THE GFS AND EC
SHOW AN IMPACT TO NE MT ON TUESDAY...BUT AGAIN...MOISTURE AND
INTENSITY ARE SIGNIFICANTLY DIFFERENT AS THE GFS DEEPENS THE SFC
LOW GREATLY COMPARED TO THE EC. AS OF NOW...850 MB TEMPERATURES
SHOW WARM AIR STRETCHING AS FAR NORTHEAST AS WESTERN ND SO
PRECIPITATION TYPE MAY BE A CHALLENGE. POPS WERE LEFT IN THE
FORECAST FOR TUESDAY AND WEDNESDAY AS IT APPEARS ENOUGH MOISTURE
AND FORCING WILL BE PRESENT. A REINFORCING SHOT OF COLD AIR WILL
FOLLOW THE FRONT BUT IT APPEARS THE BULK OF THE COLD AIR WILL BE
IN THE DAKOTAS AS THE PACIFIC RIDGE WILL HOLD ITS GROUND.
SHALLENBERGER
&&
.AVIATION...
MOSTLY VFR CONDITIONS THROUGHOUT THE PERIOD WITH A FEW POSSIBLE
SPRINKLES OF MVFR CONDITIONS IN THE GDV AND SDY AREAS OVERNIGHT.
WINDS ARE EXPECTED TO REMAIN OUT OF THE NORTHWEST TONIGHT
GAINING MORE OF A WESTERLY COMPONENT BY TOMORROW. SPEED WILL TAPER
OFF THIS EVENING TO AROUND A SPREAD OF 8 TO 13 MPH TONIGHT
INCREASING TO A SPREAD OF 11 TO 17 MPH TOMORROW. HICKS
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR FORT PECK
LAKE.
&&
$$
WEATHER.GOV/GLASGOW
