Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 110425
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
925 PM MST WED FEB 10 2016

.UPDATE...

UPPER RIDGE AXIS TO THE WEST WAS IN THE PROCESS OF BRIEFLY BEING
FLATTENED BY ENERGY RIDING ACROSS BRITISH COLUMBIA. THIS ENERGY
WAS SPREADING MID LEVEL WARM ADVECTION CLOUDS AND LIGHT PRECIP
ACROSS CENTRAL AND NORTHERN MONTANA. SOME OF THE WEAK ECHOES WERE
RIDING SOUTHEAST INTO THE NORTHERN PART OF THE CENTRAL ZONES. LOW
LEVELS WERE PRETTY DRY TO START...SO NOT EXPECTED MUCH MORE THAN A
LIGHT SNOW SHOWER OR FLURRY. ADDED THAT WORDING THE REST OF THE
EVENING FOR NORTHERN ZONES. LEFT THE REST OF THE FORECAST IN CHECK
WITH SHALLOW COLDER AIR BACKING INTO NORTHEAST MONTANA. THIS AIR
WILL EVENTUALLY ARRIVE TOWARD MORNING. THE COMBINATION OF THIS LOW
LEVEL COLD ADVECTION AND MID LEVEL WARM ADVECTION COULD PRODUCE
SOME LIGHT FREEZING PRECIP OVER THE FAR EAST AND THIS COVERED WELL
IN GOING FORECAST.

NOW FOR WINDS...STRONGEST SURFACE PRESSURE FALLS WERE MOVING INTO
NORTHEAST MONTANA THIS HOUR...WITH RISES OCCURRING OVER BRITISH
COLUMBIA. STRONGEST GRADIENT WILL BE OVERNIGHT...BUT THE
ORIENTATION OF THE GRADIENT WOULD NOT SUPPORT HIGHLIGHT LEVEL
WINDS IN LIVINGSTON. BELIEVE ENOUGH HIGHER PRESSURE WILL SURVIVE
OVER NORTHERN IDAHO TO NOT ALLOW ADVISORY LEVELS WINDS. WILL THUS
NOT ISSUE A HIGHLIGHT AT THIS TIME...DESPITE THE FACT THAT WINDS
HAVE INCREASED WITH A GUST TO 41 MPH THIS LAST HOUR. BELIEVE
GUSTS TO 50 MPH ARE POSSIBLE AND WILL THUS KEEP THE HWO IN PLACE
AND LEAVE THE GRAPHIC ON THE WEB. TWH

&&

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

WATER VAPOR IMAGERY SHOWS NW FLOW OVER OUR AREA WITH A STRONG
UPPER RIDGE ANCHORED TO OUR WEST. DEEP TROF AND MUCH COLDER AIR
EXISTS OVER THE EASTERN CONUS...BUT WE HAVE A FEW ISSUES TO WORK
OUT IN THE SHORT TERM DESPITE OUR REGION BEING DOMINATED BY THE
UPPER RIDGE.

MODEST COOL ADVECTION IS ONGOING ACROSS EASTERN MT BEHIND A WEAK
CANADIAN FRONTAL PASSAGE. A LARGE AREA OF LOW CLOUD IS APPROACHING
FROM THE NORTHERN PLAINS AS WINDS SHIFT TO THE N-NE...AND EXPECT
THIS LOW CLOUD TO GET INTO OUR EAST THIS EVENING. WATER VAPOR
IMAGERY SHOWS A WEAK SHORTWAVE MOVING INTO SOUTHERN BC WHICH MAY
BRING SOME LIGHT PCPN TO AREAS EAST OF SFC TROF LATER TONIGHT INTO
EARLY THURSDAY. SFC TEMPS SHOULD BE BELOW FREEZING BUT AN ELEVATED
WARM LAYER MAY RESULT IN A NARROW AREA OF LIGHT FREEZING RAIN...OR
A MIX OF THAT AND SNOW...FOR MAINLY FALLON COUNTY FOR A BRIEF
TIME. WILL CONTINUE TO HIGHLIGHT THIS POTENTIAL IN WX STORY AND
HWO. FURTHER WEST ACROSS MOST OF OUR CWA...DRY DOWNSLOPE WINDS
WILL PREVAIL.

SPEAKING OF FURTHER WEST...AFOREMENTIONED CANADIAN SHORTWAVE WILL
INDUCE A PERIOD OF LEE SIDE PRESSURE FALLS AND THIS WILL ENHANCE
THE GAP FLOW AT LIVINGSTON AND NYE TONIGHT. WITH MID LEVEL WINDS
IN EXCESS OF 40 KTS WE WILL SEE ADVISORY LEVEL GUSTS APPROACHED IN
THE USUAL SPOTS. HAVE PUSHED UP GUSTS TO 55 MPH BUT THERE IS SOME
UNCERTAINTY GIVEN THE CURRENT LEE SIDE PRESSURE RISES. WILL LET
EVENING SHIFT MAKE FINAL CALL WHETHER A WIND ADVISORY IS NEEDED
FOR LIVINGSTON AND NYE.

ANOTHER VERY MILD DAY IS IN STORE FOR THURSDAY WITH MIXED WESTERLY
WINDS...AND WE WILL SEE 60+ DEGREE HIGHS ONCE AGAIN. SHERIDAN
RECORD OF 61F FOR FEBRUARY 11TH WILL BE CHALLENGED.

A STRONGER AND MORE INTERESTING BACKDOOR FRONT WILL SURGE IN FROM
THE NE THURSDAY NIGHT INTO FRIDAY...AS ANOTHER PACIFIC SHORTWAVE
INTERACTS WITH ANOTHER COLD SURGE OUT OF CANADA. LATEST MODELS ARE
IN GOOD AGREEMENT SHOWING COOLER EAST WINDS PUSHING WEST OF
BILLINGS. THIS WILL BRING SIGNIFICANTLY COOLER TEMPS FOR FRIDAY
FOR ALL BUT THE MTNS AND FOOTHILLS...WITH HIGHS ONLY IN THE 30S TO
LOWER 40S. ALSO...A PERIOD OF MOIST ISENTROPIC ASCENT WILL BRING A
REASONABLE CHANCE OF SNOW/RAIN TO MUCH OF OUR LOWER ELEVATIONS
FROM LATE THURSDAY NIGHT THROUGH FRIDAY...EAST OF SFC TROF OF
COURSE...AND THIS INCLUDES BILLINGS. THIS IS SOMETHING TO
WATCH...BUT AT THIS TIME FEEL THAT WARM GROUND AND WEAK DYNAMICS
SUPPORT SNOW ACCUMS OF LESS THAN AN INCH. SFC TROF SHOULD PUSH
EAST AND OFF THE FOOTHILLS FRIDAY NIGHT AS PCPN TAPERS OFF.

ONLY OTHER POTENTIAL ISSUE IS FOG AND LIGHT FREEZING DRIZZLE FOR
OUR EAST LATE THURSDAY NIGHT INTO FRIDAY AS WE TAP INTO THE LOW
LEVEL COLDER AIR AND MOISTURE BEHIND BACKDOORING FRONT. WE COULD
SEE ENOUGH SATURATION WITH TEMPS WARMER THAN -10C TO SUPPORT SOME
FREEZING DRIZZLE.

JKL

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

SATURDAY WILL SEE THE A TROUGH MOVE THROUGH ENDING THE DOMINANCE
OF THE WEST COAST RIDGE. THE 12Z GUIDANCE DID NOT OFFER ANY
IMPROVEMENT WITH THE TIMING DISCREPANCIES. THE GFS REMAINS SLOWER
BUT SLIGHTLY STRONGER WITH THE WAVE. THE EC IS ABOUT 6 HOURS
FASTER THAN THE GFS. GIVEN THAT THE PATTERN HAS NOT
CHANGED...HAVE BASICALLY CONTINUED THE INHERITED POPS.

BEHIND THE SHORT WAVE...WINDS WILL INCREASE. 850 WINDS ARE IN THE
RANGE OF 40 KTS WITH INSTABILITY. THIS HAS COME DOWN SOME OVER THE
PAST 24 HOURS...BUT NONE THE LESS IT WILL BE BREEZY ACROSS THE
AREA. GOING INTO THE EARLY PART OF NEXT WEEK...WINDS WILL REMAIN
GUSTY. THE GFS CONTINUES TO SHOW AN EXTENDED PERIOD OF UNSTABLE
AND WINDY CONDITIONS. TEMPERATURES WILL BE MORE MODERATE THROUGH
THE EXTENDED. REIMER
&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL TONIGHT. GUSTY WSW SURFACE WINDS WILL
AFFECT BIG TIMBER AND KLVM WITH GUSTS OF 45 TO 50 KNOTS EXPECTED
AT KLVM. WIND SHEAR WILL BE A CONCERN OVERNIGHT AT OTHER
TERMINALS...INCLUDING KBIL...KMLS...AND KSHR...AS LIGHT WINDS
PERSIST AT THE SFC BELOW THE INVERSION...WHILE STRONG NORTHWEST
WINDS OF 30 TO 40 KNOTS PERSIST JUST ABOVE THE SFC. GILSTAD

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 040/064 035/042 035/057 034/051 035/059 039/059 033/056
    00/N    23/O    12/W    22/W    22/W    21/N    11/B
LVM 044/058 038/055 038/050 033/048 038/054 040/053 034/051
    00/N    33/W    23/W    43/W    32/W    21/N    12/W
HDN 031/065 030/045 030/059 030/052 031/059 034/060 028/057
    00/B    23/O    12/W    33/W    32/W    21/N    11/B
MLS 029/053 026/037 028/055 030/049 031/055 037/055 030/053
    11/E    12/S    32/W    21/B    22/W    21/N    11/B
4BQ 028/058 026/038 027/055 030/049 029/055 034/058 028/053
    01/E    13/O    22/W    32/W    22/W    21/N    11/B
BHK 025/044 022/030 020/045 028/045 028/048 034/051 026/048
    33/O    11/Z    33/W    32/W    22/W    21/N    11/B
SHR 030/060 029/046 029/054 029/046 029/054 033/056 027/053
    00/B    22/O    12/W    32/W    22/W    11/B    11/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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