000
FXUS65 KBYZ 032201
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
301 PM MST WED DEC 3 2008
.SHORT TERM...VALID FOR THU AND FRI...
SHORTWAVE MOVING S THROUGH ALBERTA THIS AFTERNOON...PER WATER VAPOR
IMAGERY...WILL MOVE S INTO MT TONIGHT THROUGH THU MORNING. MODELS
DID NOT SHOW MUCH Q VECTOR CONVERGENCE WITH THE SYSTEM...BUT DID
GENERATE LIFT OVER NORTHERLY UPSLOPE AREAS AND SE MT. HAVE INCREASED
POPS TO LIKELY OVER THE SW FOOTHILLS AND NE FACING SLOPES OF
BEARTOOTHS/ABSAROKAS...AS WELL AS THE NE BIG HORNS. ALSO RAISED POPS
OVER S BIG HORN COUNTY AND KSHR AREA. THE FAVORABLE DENDRITIC GROWTH
LAYER WAS VERY LOW IN THE ATMOSPHERE DUE TO THE COLD AIRMASS OVER THE
AREA. THUS SNOW AMOUNTS SHOULD BE LOW TONIGHT. SNOW WILL TAPER OFF
AROUND KBHK THROUGH THE EVENING AS THE AIRMASS BECOMES MORE STABLE.
TEMPERATURE FORECAST IN THE SINGLE DIGITS TONIGHT WAS IN GOOD SHAPE
WITH 850 MB TEMPERATURES IN THE NEGATIVE TEENS C.
STRONG JET ALOFT WILL MOVE OVER THE AREA DURING THU BRINGING
INCREASINGLY ANTICYCLONIC FLOW. THE SHORTWAVE WILL DEPART THE AREA
EARLY ON THU. LOW LEVEL MOISTURE WILL SLOWLY DECREASE OVER THE AREA.
TIME-HEIGHT CROSS SECTIONS SHOWED A STABLE AIRMASS WITH NO LIFT SO
WILL KEEP THE DRY FORECAST. HOWEVER...WEAK LIFT AND NORTHERLY FLOW
WILL BE OVER THE SW IN THE MORNING WITH LINGERING MOISTURE
SUPPORTING A SLIGHT CHANCE OF SNOW. MOISTURE WITH NORTHERLY FLOW
WILL ALSO BRING A SLIGHT CHANCE OF SNOW...MAINLY IN THE MORNING...TO
THE CRAZYS AND NE BIG HORNS. WILL REMOVE AFTERNOON POPS SW AS
AIRMASS SHOULD BE TOO DRY FOR PRECIPITATION BY THAT TIME. 850 MB
TEMPERATURES ON BOTH THE WRF AND GFS RANGED FROM -8 DEGS C W TO -15
DEGS C NE...SUPPORTING HIGHS ONLY IN THE TEENS TO AROUND 20 DEGREES.
THU NIGHT WILL BE DRY UNDER ANTICYCLONIC FLOW AND LEE TROUGHING
SETTING UP AT THE SURFACE. MAY END UP NEEDING A WIND ADVISORY FOR
GAP FLOW AREAS BUT HIGH PRESSURE WAS FORECAST OVER ID WHICH MAY KEEP
THE PRESSURE GRADIENT TOO NW TO SE ORIENTED. WILL CONTINUE TO
HIGHLIGHT POSSIBILITY IN HWO. LOW TEMPERATURES WILL LIKELY OCCUR
EARLY IN THE NIGHT...WITH STEADY TO RISING TEMPERATURES THEREAFTER.
WEAK SHORTWAVES ACCOMPANIED BY PACIFIC MOISTURE AND WARM ADVECTION
WILL MOVE SE INTO THE REGION FRI THROUGH FRI NIGHT IN NW FLOW ALOFT. FRI
MORNING WAS DRY ON TIME-HEIGHT CROSS SECTIONS SO WENT MOSTLY DRY.
KEPT THE SLIGHT CHANCE E FOR FRI AFTERNOON ALONG WITH LOW MOUNTAIN
POPS. MOISTURE WILL BE SLOW TO SATURATE LOW LEVELS FRI NIGHT SO
DRIED OUT LOW ELEVATIONS WEST. LOWER LEVELS WERE MOIST OVER THE E SO
KEPT THE LOW POPS THERE. IT WILL BE MUCH WARMER THAN THU ON
FRI...BUT MODELS DIFFERED A BIT IN THEIR 850 MB TEMPERATURE FORECAST
WITH WRF RUNNING COOLER THAN THE GFS. GOING FORECAST REPRESENTED A
COMPROMISE BETWEEN THE TWO MODELS. THE THREAT FOR STRONG WINDS IN
THE GAP AREAS WILL LINGER INTO FRI BEFORE SURFACE LOW STARTS TO PULL
E. FRI NIGHT TEMPERATURES LOOKED REASONABLE. ARTHUR
.LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED...
MODELS IN FAIRLY GOOD AGREEMENT THROUGH THE WEEKEND WITH UPPER
LEVEL DISTURBANCES BUT DIFFER SOMEWHAT ON TIMING AND EXACT
LOCATIONS. NORTHWEST FLOW ALOFT WILL BE OVER THE FORECAST AREA
SATURDAY AND SUNDAY. A FEW WAVES WITHIN THE FLOW MOVE OVERHEAD
BRINGING SLIGHT PRECIP CHANCES. ALTHOUGH LEE-SIDE TROUGHING SETS
UP BRINGING WINDY CONDITIONS TO THE WESTERN ZONES AND THIS
DOWNSLOPING MAY HINDER PRECIP. A STRONGER DISTURBANCE IS PROGGED
TO MOVE OVER THE FORECAST AREA SUNDAY AND SUNDAY NIGHT BRINGING A
BETTER CHANCE FOR PRECIP. HOWEVER...MODELS NOT IN THE BEST
AGREEMENT WITH STRENGTH AND TIMING. NORTHWEST FLOW ALOFT WILL
CONTINUE INTO EARLY NEXT WEEK. STREAMWISE VORTICITY WILL BE
MOVING OVERHEAD BUT MOISTURE LOOKS LIMITED SO WILL LEAVE CLIMO
POPS ACROSS THE BOARD. TEMPERATURES LOOK TO BE WARMING BACK INTO
THE 30S AND 40S THROUGH THE PERIOD. BUT COLD AIR BOUNDARY WILL BE
SITUATED NEAR BAKER SO TEMPERATURES BETWEEN MILES CITY AND BAKER
WILL BE TRICKY. AREAS FROM BILLINGS ON WEST WILL SEE MAINLY A
DOWNSLOPE FLOW RESULTING IN TEMPERATURES IN THE 40S. HOOLEY
&&
.AVIATION...
LIGHT SNOW WILL BE POSSIBLE ACROSS THE FORECAST AREA TONIGHT. THE
BEST CHANCES WILL BE ACROSS THE MOUNTAINS...AS WELL AS THE
FOOTHILLS LOCATIONS OF THE BEARTOOTH/ABSAROKA AND BIG HORN
RANGES. VFR CONDITIONS WILL PREVAIL ACROSS THE PLAINS WITH SOME
MVFR CONDITIONS WITHIN ANY SNOW SHOWER ACTIVITY. MOUNTAIN
OBSCURATIONS WILL CONTINUE THROUGHOUT THE NIGHT. HOOLEY
&&
.PRELIMINARY POINT TEMP/POPS...
THU FRI SAT SUN MON TUE WED
-----------------------------------------------------------
BIL 008/021 014/043 027/046 028/047 029/042 023/047 024/047
30/U 00/N 02/W 22/W 22/W 22/W 22/W
LVM 005/021 014/041 031/047 039/050 031/038 020/047 025/047
30/U 00/N 13/W 32/W 33/W 22/W 22/W
HDN 007/021 008/042 023/044 024/046 024/041 021/048 023/048
30/U 00/B 02/W 22/W 22/W 22/W 22/W
MLS 007/019 006/041 022/036 021/041 024/035 019/040 024/040
20/B 02/O 22/J 22/J 22/J 22/J 22/J
4BQ 007/018 005/038 023/041 022/045 021/036 019/045 024/042
30/B 02/O 22/W 22/W 22/J 22/W 22/W
BHK 003/017 003/034 021/032 022/040 021/028 017/034 021/032
30/B 02/S 22/J 22/J 22/J 22/J 22/J
SHR 005/018 004/042 022/046 022/049 022/038 018/047 023/047
50/B 00/B 03/W 22/W 22/J 22/W 22/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
