FXUS65 KBYZ 102151
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
251 PM MST THU DEC 10 2009
.SHORT TERM...VALID FOR FRI AND SAT...
WARMING TREND ON SOLID FOOTING OVER THE REGION THIS AFTERNOON AS
WESTERLY WINDS ARE PUSHING THE ARCTIC AIRMASS EAST OF THE REGION.
NORTHWESTERLY FLOW ALOFT WITH WEAK DISTURBANCES PASSING OVER
MONTANA BUT SNOWFALL LIMITED TO THE MOUNTAINS AND EASTERN PORTIONS
OF SOUTHEAST MONTANA. KGGW RADAR SHOWS ACTIVITY IS GENERALLY LESS
INTENSE AND KBHK OBS ARE SHOWING IMPROVING VISIBILITIES SO THINK
THAT ISOLATED SNOW SHOWERS IN THE FORECAST TONIGHT WILL BE
ADEQUATE. ELSEWHERE 15 DEGREE DEWPOINT DEPRESSIONS ARE KEEPING ANY
FLURRIES FROM HITTING THE GROUND SO HAVE ELIMINATED POPS FROM THE
REST OF THE AREA EXCEPT FOR MOUNTAINS. BIGGER CONCERN CONTINUES TO
BE WINDS ALONG AN AREA FROM HARLOWTON TO BIG TIMBER TO LIVINGSTON.
ANOTHER ROUND OF PRESSURE FALLS EXPECTED TONIGHT IN RESPONSE TO
ANOTHER WAVE ROTATE AROUND THE POLAR LOW OVER NORTHERN
SASKATCHEWAN BUT FLOW IS BEGINNING TO BACK OVER THE REGION. THIS
CAUSES THE PRESSURE FALLS TO BECOME MORE DIFFUSED ACROSS THE AREA
SO WHILE GRADIENTS TO GET MAINTAINED TONIGHT THINK THAT THEY WILL
CONTINUE TO PUSH ADVISORY CRITERIA AND NOT CLEARLY EXCEED CURRENT
SPEEDS. EXPECT TEMPERATURES TO AGAIN BE WARMER OVERNIGHT WITH
MIXING CONTINUING BUT WITH DEWPOINTS LOW ENOUGH AND SNOW COVER
SHOULD SEE SOME FALLS. FRIDAY WINDS CONTINUE AND AIRMASS DRIES OUT
AS BACKING FLOW ALOFT BECOMES MORE DOWNSLOPE SO PRECIPITATION
CONTINUES TO BE LIMITED TO THE MOUNTAINS. THIS WESTERLY FLOW WILL
BRING EVEN WARMER TEMPERATURES AND EXPECT READINGS TO REACH THE
MID 20S EXCEPT OVER SOUTHEAST MONTANA WHILE LOW LEVEL FLOW WILL BE
A BIT MORE SOUTHEASTERLY AND DRAW SOME COOLER AIR BACK IN FROM THE
DAKOTAS. FRIDAY NIGHT LEESIDE TROUGHING IS MAINTAINED WITH
TEMPERATURES EVEN WARMER. A WEAK WAVE MOVING ACROSS THE EASTERN
PACIFIC INFUSES MOISTURE INTO THE FLOW PATTERN AND WILL SEE AND
INCREASE IN MOUNTAIN SNOWFALL TOWARDS MORNING...BUT ONLY FOR
WESTERLY ORIENTED OROGRAPHIC AREAS AS FLOW ALOFT IS CONFLUENT.
DOWNSLOPE WINDS CONTINUE TO MAKE THE WESTERLY HALF OF THE AREA
WARMER WITH TEMPERATURES LIKELY TO RISE TO NEAR FREEZING. LIGHTER
WINDS WITH LESS MIXING SHOULD CAUSE SOUTHEAST MONTANA TO REMAIN
COOLER AND PROBABLY STRUGGLE TO REACH 20. PATTERN BECOMES MORE
FAVORABLE FOR SNOW OVER THE MOUNTAINS WITH PLAINS STILL LOOKING
DRY. SATURDAY NIGHT THE APPROACH OF THE PACIFIC WAVE CAUSES SOME
WEAK CYCLOGENESIS OVER THE AREA BUT THIS SERVES TO PULL IN DRY AIR
FROM THE SOUTH SO DESPITE MIDLEVEL MOISTURE INCREASING ONLY SEE A
SLIGHT CHANCE FOR SNOW. WINDS AND CLOUDS OVER SOUTHERN MONTANA AND
NORTH CENTRAL WYOMING SHOULD KEEP TEMPERATURES CLOSE TO 20...WHICH
WILL ONLY SERVE TO MAKE SUNDAYS ARCTIC ARRIVAL A RUDER SHOCK. BORSUM
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
MAIN ISSUES FOR THE EXTENDED PERIOD CONTINUES TO BE GETTING A
READ ON THE NEXT ARCTIC MOVING INTO THE REGION. CURRENT TIMING
LOOKS LIKE THIS SYSTEM SHOULD MOVE INTO THE REGION SUNDAY
EVENING/NIGHT. MOVING QUICKLY ACROSS THE REGION AND OUT BY
WEDNESDAY NIGHT. THIS SYSTEM WILL BRING A GOOD CHANCE FOR PRECIP
TO THE REGION...ESPECIALLY WITH PREFRONTAL WARMUP THROUGH THE
EARLY PART OF THE WEEKEND.
ARCTIC WILL HOLD OFF A BIT SUNDAY...BUT HIGHS WILL LIKELY COME
EARLY WITH COOL AIR SEEPING INTO THE AREA...AND SNOW SPREADING
INTO THE REGION. DID RAISE TEMPS SLIGHTLY...MAINLY ACROSS
SOUTHERN ZONES. CHANCES FOR PRECIP LOOK GOOD WITH THIS
SYSTEM...BUT STILL DO NOT EXPECT LARGE SNOW ACCUMULATIONS AT THIS
TIME...AGAIN DUE COLD TEMPS AS WITH PREVIOUS ARCTIC.
HOWEVER...BEST ACCUMULATIONS SHOULD AGAIN COME ALONG THE LEADING
EDGE OF THE FRONT BEFORE COLD SETS IN...ESPECIALLY BETWEEN 18Z
SUNDAY AND 06Z MONDAY...AT THIS TIME. HAVE RAISED POPS
DRASTICALLY THROUGH MONDAY MORNING AND INTO EARLY AFTERNOON WITH
CURRENT GRID CONSISTENCY. PRECIP WITH THE SYSTEM SHOULD BE
CLEARING OUT BY MONDAY EVENING...WITH COLD AIR CLEARING FROM WEST
TO EAST THROUGH WEDNESDAY. ARCTIC APPEARS TO TAKE A PRETTY DEEP
CUT INTO THE REGION BY MONDAY...DID DROP TEMPS FOR MONDAY AND
MONDAY NIGHT WITH THIS SYSTEM. MAY NOT BE QUITE ENOUGH...BUT
SHOULD BE A GOOD START.
RIDGE BEGINS BUILDING INTO THE AREA BY TUESDAY AFTERNOON...DRYING
THE AREA OUT AND AFFECTING A GRADUAL WARMUP FROM WEST TO EAST
WITH HIGHS NEAR FREEZING IN KBIL WEDNESDAY...AND LOW TO MID 40S
THURSDAY. GILSTAD
&&
.AVIATION...
VFR FLIGHT CONDITIONS WILL PREVAIL UNDER PARTLY CLOUDY
SKIES THROUGH THE NIGHT. SNOW SHOWERS ARE LETTING UP IN THE EAST AND
GUSTY WESTERLY WINDS ARE BEGINNING TO LET UP...BUT WILL STILL SEE
GUST OF 20 TO 30 KTS. WINDS ARE EXPECTED TO PICK UP AGAIN EARLY IN
THE MORNING...WITH GUSTS OF 30 TO 40 KTS...FROM K3HT TO KLVM ALONG
THE EASTERN SLOPES OF THE CRAZY AND BEARTOOTH/ABSAROKA MOUNTAINS.
20 TO 30 KT GUSTS WILL SPREAD EASTWARD TO AROUND KBIL BY TOMORROW
AFTERNOON. GILSTAD
&&
.PRELIMINARY POINT TEMP/POPS...
FRI SAT SUN MON TUE WED THU
-----------------------------------------------------------
BIL 004/025 011/030 016/025 004/013 002/024 015/029 023/042
00/N 11/E 25/S 43/S 21/B 11/B 11/N
LVM 010/028 015/034 019/024 010/022 008/031 020/033 025/042
10/N 12/J 24/S 43/S 22/S 11/N 11/N
HDN 003/025 004/028 012/023 902/016 908/022 007/026 014/037
00/B 11/B 24/S 42/S 21/B 11/B 11/B
MLS 902/019 902/018 003/015 904/007 910/015 002/020 011/033
10/B 12/J 23/S 53/S 11/B 11/B 11/B
4BQ 901/025 003/026 008/022 901/011 907/018 006/024 015/036
10/B 11/E 22/S 53/S 11/B 11/B 11/B
BHK 903/018 902/015 003/016 906/007 910/013 003/018 010/030
20/B 12/J 22/S 42/S 11/B 11/U 11/B
SHR 902/026 009/033 013/030 004/019 902/025 010/030 015/040
10/B 11/B 23/S 43/S 21/B 11/B 11/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
