Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 211025
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
325 AM MST WED JAN 21 2015

.SHORT TERM...VALID FOR TDY AND THU...

SHORT WAVE IN NORTHERLY FLOW ALOFT WAS PASSING OVER OUR EASTERN
ZONES OVERNIGHT. LIGHT SNOW SHOWERS WERE INDICATED AT TIMES ON
BOWMAN RADAR AND FROM BAKER SURFACE OBSERVATIONS. THIS MAY
CONTINUE TO PRODUCE SOME SPOTTY LIGHT SNOW OVER OUR DAKOTA BORDER
AREA EARLY TODAY...BUT OTHERWISE WE SHOULD SEE DRY CONDITIONS
PREVAIL BEHIND THIS SYSTEM WITH FLOW ALOFT BECOMING ANTI-CYCLONIC
AS A MID LEVEL RIDGE BUILDS OVER THE REGION THROUGH THURSDAY.

THE PRIMARY WEATHER FEATURE WILL ONCE AGAIN BECOME WIND IN OUR
WESTERN ZONES. PROGGS SUGGEST LEE SIDE SURFACE TROUGHING WILL
OCCUR LATE THIS EVENING IN SOUTH CENTRAL MONTANA. I EXPECT THE
AFFECTS OF THIS TO BE SEEN AT NYE AND LIVINGSTON OVERNIGHT WITH
INCREASING SOUTHWEST WINDS. THE PRESSURE FALLS ON THE ORDER OF ONE
OR TWO MB PER 6 HOURS DOES NOT IMPRESS ME. LOCAL RESEARCH AIDS DO
NOT SUGGEST A SLAM DUNK PROBABILITY OF HIGHLIGHT CRITERIA EITHER
AS FLOW MAY HAVE TOO MUCH OF A WESTERLY COMPONENT FOR TRUE GAP
EFFECTS. BY LATE THURSDAY THE GRADIENT MAY TURN WESTERLY ENOUGH TO
ACTUALLY FAVOR THE HARLOWTON TO BIG TIMBER CORRIDOR. AT THIS TIME
WE WILL CONTINUE THE HAZARDOUS WEATHER OUTLOOK FOR THE AREA AND
ALSO PRODUCE A WEATHER STORY REGARDING WINDY CONDITIONS IN THE
WEST FOR THE WEBSITE...BUT HOLD OFF ON ANY HIGHLIGHTS TO SEE IF
PROGGS TREND THE PRESSURE FALLS TO FAVOR A STRONGER AND MORE
SOUTHWEST GRADIENT.

PASSAGE OF MID LEVEL SHORTWAVE SHOULD BEGIN TO REDUCE THE WIND
ALONG OUR FOOTHILLS THURSDAY NIGHT...THOUGH IT WILL BE SOMEWHAT
BREEZY ACROSS THE ENTIRE CWA. THAT SHORT WAVE MAY ALSO BRING
ISOLATED SNOW SHOWERS/FLURRIES ACROSS THE FORECAST AREA.

AS FOR TEMPERATURES...LESS DOWNSLOPING/MIXING SHOULD BRING OUR
COOLEST DAY OF THE WEEK TODAY...WITH HIGHS RANGING FROM THE UPPER
20S ALONG THE DAKOTAS BORDER TO MID 30S IN OUR WEST. WE WILL BEGIN
TO TREND WARMER WITH THE INCREASING DOWNSLOPE FLOW THURSDAY. BT

.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE...

INTEGRATED WATER VAPOR TRANSPORT FORECAST FROM THE GEFS/GFS STILL
TARGETS THE WEEKEND FOR AN ATMOSPHERIC RIVER TO AFFECT THE AREA.

BEFORE THE WEEKEND...A WEAK WAVE WILL MOVE THROUGH ANTICYCLONIC
FLOW ON FRI WITH A FAIRLY DRY AIRMASS IN PLACE. JUST EXPECTING A
SLIGHT CHANCE OF SHOWERS ACROSS THE FAR SOUTHERN ZONES IN THE
MORNING WITH THE WAVE. ADDITIONAL WEAK ENERGY WILL MOVE THROUGH
THE AREA FRI NIGHT AS A PACIFIC JET APPROACHES THE AREA. JET
DIVERGENCE WILL BRING A SLIGHT CHANCE OF PRECIPITATION LATE FRI
NIGHT TO AREAS W OF KBIL. THE LEE TROUGH WILL TIGHTEN UP AGAIN
BRINGING WINDY CONDITIONS W OF KBIL.

THE JET DIVES SE INTO THE AREA SAT ACCOMPANIED BY JET DIVERGENCE
AND A DECENT SHORTWAVE. HOWEVER...THE ECMWF BRINGS THE WAVE INTO
THE DAKOTAS WHILE THE GFS KEEPS IT OVER THE FORECAST AREA. THE GFS
BRINGS A QUICK SHOT OF MOISTURE TO THE AREA WITH THE DYNAMICS. THE
CANADIAN MODEL BROUGHT SOME QPF TO THE AREA AS WELL. THE ECMWF WAS
DRIER FOR SAT. DESPITE THE ATMOSPHERIC RIVER...THERE WILL BE
UNCERTAINTY FOR SAT...SO HAVE NUDGED POPS TOWARD THE SUPERBLEND
GUIDANCE. 850 MB TEMPERATURES SUGGEST THAT IF THE GFS IS
CORRECT...PRECIPITATION WILL BE MOSTLY RAIN WITH SOME MIXED RAIN
AND SNOW. THE ECMWF WOULD KEEP ANY PRECIPITATION ALL RAIN. THE
PACIFIC JET PUSHES OFF TO THE E SAT NIGHT AND SOME PRECIPITATION
WILL LINGER OVER THE AREA. THE JET CONTINUES TO PUSH OFF TO THE E
THROUGH MON AND UPPER RIDGING BUILDS OVER THE REGION. THE WEATHER
WILL TURN DRY AFTER SOME MOUNTAIN SHOWERS ON SUN. PACIFIC MOISTURE
WILL MOVE INTO THE MOUNTAINS ON WED BRINGING A CHANCE OF SHOWERS.

TEMPERATURES WILL BE ABOVE NORMAL THROUGH THE EXTENDED PERIOD WITH
THE WARMEST DAY EXPECTED TO BE MON WHEN HIGHS COULD REACH THE 50S.
ARTHUR

&&

.AVIATION...

MVFR AND SOME IFR CONDITIONS WILL OCCUR OVER SE MT FROM KMLS E
AND S THIS MORNING AS SNOW SHOWERS MOVE THROUGH THE AREA. IN
ADDITION...THERE WILL BE AREAS OF MOUNTAIN OBSCURATION OVER THE NE
BIG HORNS. VFR WILL RETURN TO THE ENTIRE AREA THIS AFTERNOON AND
CONTINUE THROUGH TONIGHT. W TO SW SURFACE WINDS WILL INCREASE
TONIGHT OVER AREAS W OF KBIL. ARTHUR

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY THU     FRI     SAT     SUN     MON     TUE
-------------------------------------------------------
BIL 032 020/042 028/043 031/047 035/048 034/050 034/046
    0/B 00/N    11/B    12/W    21/B    10/B    11/U
LVM 033 019/044 027/044 031/047 035/050 036/053 036/050
    0/U 00/N    11/N    22/W    21/B    10/N    11/U
HDN 032 010/041 021/042 024/046 029/048 028/048 027/045
    0/B 00/B    11/B    13/W    21/B    11/B    11/U
MLS 030 014/038 026/040 028/045 031/044 029/047 028/042
    2/J 00/B    11/B    12/W    11/B    11/B    11/U
4BQ 031 012/039 024/041 026/046 031/045 030/047 028/045
    2/J 00/B    01/B    12/W    21/B    11/B    11/U
BHK 029 014/038 025/039 026/043 028/042 028/045 028/041
    4/J 00/B    01/B    12/W    21/N    11/B    11/U
SHR 031 007/040 020/042 022/046 028/047 029/049 027/046
    1/B 00/B    11/B    02/W    21/B    11/U    11/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


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