Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 032157
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
257 PM MST WED FEB 3 2016

.SHORT TERM...VALID FOR THU AND FRI...

SHORTWAVE TROUGH MOVING ONTO THE WESTERN COAST WAS INDUCING
SURFACE PRESSURE FALLS OVER THE NORTHERN ROCKIES. THIS WILL
TIGHTEN A LEE TROUGH AND DEVELOP STRONG WINDS AT LIVINGSTON AND
NYE OVERNIGHT. WIND FORECAST TRICKY OVER THE WEST AS THE TROUGH
DOES SEND QUITE A BIT OF ENERGY INTO IDAHO AND THIS MAY CAUSE TOO
MUCH IN THE WAY OF SURFACE PRESSURE FALLS OVER THE GREAT BASIN FOR
ADVISORY LEVEL WINDS. ANOTHER THOUGHT...HOWEVER...IS FOR THE QUICK
ERODING OF SURFACE HIGH PRESSURE OVER NORTHERN IDAHO WOULD ALLOW
FOR THE PROPER GRADIENT TO FORM OVER WESTERN VALLEYS. LOCAL
GUIDANCE PRODUCTS WERE TRENDING UPWARD FOR WIND SPEED AND THE NAM
MODEL WAS HITTING LIVINGSTON HARD WITH WIND OVERNIGHT AND THURSDAY
MORNING. WILL BE CLOSE BUT DECIDED TO ISSUE AN ADVISORY FOR THIS
EVENT THROUGH THROUGH MORNING FOR THE UPPER YELLOWSTONE AND UPPER
STILLWATER RIVER VALLEYS.

THE SHORTWAVE TROUGH CRASHES THROUGH THE AREA THURSDAY AND THIS
WILL GENERATE LOW TO MID LEVEL COLD AIR ADVECTION WHICH WILL SHUT
THE WINDS OFF OVER THE WEST BY NOON. THE SPLITTING NATURE OF THE
TROUGH WILL LIMIT THE LARGE SCALE ASCENT FOR THIS SYSTEM ON
THURSDAY BUT ENOUGH INSTABILITY WITH 850-500MB LAPSE RATES NEAR
8C/KM AND SOME MOISTURE FOR A FEW SHOWERS. MODELS WERE KEEPING
POPS EAST OF BILLINGS AS DOWNSLOPE WINDS KEEP MOST OF THE CENTRAL
ZONES DRY. A SECONDARY SHORTWAVE CRUISES INTO EASTERN MONTANA
THURSDAY NIGHT FOR ANOTHER ROUND OF SNOW SHOWERS. COULD BE A QUICK
INCH OF SNOW ACCUMULATION IN SPOTS.

FRIDAY WILL BE DRY AS AN UPPER RIDGE SHIFTS IN. THIS RIDGE GETS
SHUNTED EAST AND FLATTENED LATE FRIDAY NIGHT AND ALLOW FOR
MOISTURE AND ASCENT TO ENTER INTO THE WESTERN MOUNTAINS. A LEE
TROUGH WILL FORM AND TIGHTEN AGAIN FRIDAY AND FRIDAY NIGHT WITH
ADVISORY LEVEL WINDS POSSIBLE FRIDAY NIGHT INTO SATURDAY OVER THE
WESTERN VALLEYS. TWH

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

ANOTHER WEAK SHORTWAVE WILL MOVE THROUGH LATE SAT INTO EARLY
SUN... AS PER GFS AND EURO GUIDANCE. THIS WILL BRING A CHANCE OF
SNOW TO THE MOUNTAINS AND POSSIBLY ACROSS THE PLAINS IF THE WETTER
GFS SOLUTION OCCURS. PRECIP WILL HAVE TO OVERCOME STRONG WEST
WINDS AND DOWNSLOPING HOWEVER. THIS INFLUENCE WILL MAINLY BE IN
WESTERN ZONES AND COULD PUSH AS FAR EAST AS BILLINGS. THE
REMAINDER OF THE PERIOD LOOKED DRY OUTSIDE OUR EASTERN ZONES
WHERE RAIN/SNOW MAY FORM IN THE COLD AIR SURGE WITHIN THE N-NW
UPPER LEVEL FLOW ON LATE MON THROUGH TUES... DEPENDING ON
PLACEMENT OF THIS SURGE.

WINDS GUST OVER 60 MPH ARE POSSIBLE IN THE GAP FLOW AREAS EARLY
SAT... THEN TRANSITIONING TO A POST FRONT WIND EVENT WITH GUSTS
TO 50 MPH SAT NIGHT AND INTO SUN MORNING... ESPECIALLY FOR
BILLINGS AND W... THEN REMAINING GUSTY FOR THE REMAINDER OF SUN
ACROSS MOST OF OUR AREA. GUSTS MAY BE HIGHER IF SHOWERS MIX DOWN
FASTER MID-LEVEL FLOW.

WITH CONTINUING DOWNSLOPE FLOW... THE EARLY PART OF NEXT WEEK WILL
BE WARM FOLLOWING THE WEAK COLD FRONT OVER THE WEEKEND. THERE IS
STILL UNCERTAINTY ASSOCIATED WITH STRENGTH AND PLACEMENT OF THE
HIGH AMPLITUDE RIDGE ACROSS THE WEST. THIS COULD FORCE THE COLD
AIR SURGE FURTHER EAST AND KEEP THE AREA WARMER THAN FORECAST...
BUT GIVEN UNCERTAINTIES ON WHERE THIS GRADIENT WILL SET UP... HAVE
TAKEN THE BLENDED GUIDANCE FOR NOW. MROWELL

&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL OVER THE NEXT 24 HOURS. EXPECT WINDS
AROUND KLVM TO BE INCREASING THROUGH THE DAY WITH GUSTS OVER 40
MPH LIKELY BY MIDNIGHT. MROWELL

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 022/041 028/045 032/048 030/043 029/051 033/057 033/051
    01/N    10/N    02/W    22/W    01/N    10/N    00/N
LVM 023/037 024/039 029/042 028/040 029/047 033/050 035/047
    13/W    31/N    13/W    31/N    11/N    01/N    10/N
HDN 014/042 025/045 026/048 025/042 023/048 026/053 027/049
    01/E    21/B    02/W    22/W    01/E    10/U    00/B
MLS 015/041 025/045 029/049 029/042 025/043 028/049 028/045
    02/W    20/B    02/W    41/N    02/W    21/B    00/B
4BQ 013/040 025/043 025/049 027/040 023/044 026/052 027/046
    02/W    21/B    03/W    31/N    01/N    21/B    00/B
BHK 011/037 024/041 026/047 027/038 021/039 023/046 023/041
    02/J    32/J    02/W    41/N    02/J    21/B    01/B
SHR 007/037 021/041 022/047 025/039 021/047 026/054 025/049
    01/E    11/B    03/W    32/W    01/E    10/U    00/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO NOON MST
      THURSDAY FOR ZONES 65-66.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


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