Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 231527
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
827 AM MST TUE DEC 23 2014

.UPDATE...

NO UPDATES PLANNED FOR THIS MORNING AS THE INHERITED FORECAST
IS IN GREAT SHAPE. LOCATIONS IN FAR SOUTHEASTERN MONTANA MAY SEE A
AN OCCASIONAL SNOW SHOWER THIS MORNING. WINDS WILL PICK UP NEAR
LIVINGSTON AND IN THE BEARTOOTH FOOTHILL AREAS THIS AFTERNOON.
SINGER

&&

.SHORT TERM...VALID FOR TDY AND WED...

MODELS IN GOOD AGREEMENT THIS MORNING WITH A SNOW EVENT FOR
WEDNESDAY NIGHT THROUGH CHRISTMAS DAY. THE OUTLIER SOLUTION FROM
THE GFS YESTERDAY IS GONE AND THE GFS IS NOW IN AGREEMENT WITH THE
REMAINING MODELS RESULTING IN HIGH CONFIDENCE IN THE SHORT TERM
FORECAST THROUGH CHRISTMAS NIGHT.

TODAY...UNSTABLE NORTHWEST FLOW CONTINUES ACROSS THE AREA THIS
MORNING. AS A RESULT THERE IS A CONTINUING SLIGHT CHANCE OF SNOW
SHOWERS THIS MORNING...MAINLY OVER FOOTHILLS AND MOUNTAINS AS WELL
AS ALONG THE EASTERN STATE LINE. BY THIS AFTERNOON DRIER AIR AND
BACKING FLOW ALOFT WILL BRING DRY CONDITIONS AND DECREASING CLOUDS
TO THE AREA. THE BACKING WINDS ALOFT WILL GENERATE LEE SIDE
TROFFING WHICH WILL BEGIN TO INCREASE WINDS IN FAVORED GAP FLOW
REGIONS AROUND LIVINGSTON AND NYE. EXPECT TO SEE GUSTS IN
LIVINGSTON AND NYE AROUND 50 MPH BY LATE AFTERNOON...WITH GUSTS
UP TO 70 MPH TONIGHT. ISSUED A WIND ADVISORY FOR THESE AREAS
STARTING AT 6 PM. THOSE DRIVING THROUGH THESE AREAS SHOULD BE
PREPARED FOR DANGEROUS CROSSWINDS AND ANY HIGH PROFILE VEHICLES
MAY WANT TO CHOOSE AN ALTERNATE ROUTE TONIGHT.

WEDNESDAY...A PREFRONTAL DAY TUESDAY WILL BE THE WARMEST DAY OF
THE WEEK. GUSTY SOUTHWEST WINDS OVER THE WESTERN FOOTHILLS WILL
SPILL OUT INTO THE PLAINS DURING THE AFTERNOON. THIS SHOULD PUSH
TEMPERATURES AT LEAST BRIEFLY INTO THE LOW TO MID 40S. CLOUD COVER
WILL BE ON THE INCREASE THROUGH THE DAY AND THAT MAY KNOCK A
COUPLE DEGREES OFF THE FORECAST HIGHS BUT WENT A FEW OVER GUIDANCE
TO ACCOUNT FOR PRE-FRONTAL WARMING. FOR THE MOST PART WEDNESDAY
WILL BE DRY...BUT BY LATE WEDNESDAY AFTERNOON WILL BEGIN TO SEE
PRECIPITATION DEVELOP OVER WESTERN AND NORTHERN ZONES AS A COLD
FRONT PUSHES INTO THE AREA. STRONG GAP FLOW WINDS WILL CONTINUE
OVER WESTERN VALLEYS UNTIL THE COLD FRONT MOVES THROUGH LATE
AFTERNOON/EARLY EVENING. WIND ADVISORY CONTINUES FOR THESE AREAS
UNTIL 6 PM WEDNESDAY.

WEDNESDAY NIGHT AND CHRISTMAS...COLD FRONT PUSHES THROUGH THE AREA
EARLY EVENING WEDNESDAY WITH PRECIPITATION DEVELOPING ALONG THE
FRONT. PRECIPITATION COULD START OUT AS RAIN IN SOME LOCATIONS
BEFORE TURNING OVER TO ALL SNOW ACROSS THE AREA BY MIDNIGHT.
DIVERGENCE ALOFT COMBINED WITH DECENT QG FORCING AND GOOD UPSLOPE
WINDS SHOULD BRING A PERIOD OF ACCUMULATING SNOW FROM MIDNIGHT
THROUGH MID AFTERNOON ON CHRISTMAS. GENERAL 2 TO 4 INCH AMOUNTS
SEEM REASONABLE FOR LOWER ELEVATION LOCATIONS WEST OF A MILES CITY
TO BROADUS LINE...WITH AN INCH OR TWO TO THE EAST. NORTH FACING
MOUNTAINS AND FOOTHILLS COULD SEE SIGNIFICANTLY MORE SNOW DUE TO
10 TO 20 MPH UPSLOPE NORTHERLY WINDS. 15 TO 1 SNOW RATIOS AND
CURRENT QPF FORECASTS WOULD YIELD 4 TO 8 INCHES FOR FOOTHILLS
LOCATIONS FROM LIVINGSTON TO RED LODGE AND THE SHERIDAN FOOTHILLS.
MAY NEED A FEW SNOW ADVISORIES AND CAN`T RULE OUT A HEAVY SNOW
WARNING IN THESE UPSLOPE AREAS WITH THIS SYSTEM AS CURRENT SNOW
ACCUMULATION GRIDS INDICATE. HOWEVER THERE IS STILL A BIT OF TIME
TO MAKE THAT DECISION WITH SNOW NOT STARTING UNTIL TOMORROW
NIGHT...SO WILL PUNT THAT TO THE FOLLOWING SHIFTS WHO CAN TAKE A
LOOK AT THE LATEST MODEL DATA. TEMPERATURES ON CHRISTMAS WILL FALL
SLOWLY FROM AROUND 30 INTO THE MID 20S THROUGH THE DAY AS COLDER
AIR BUILDS IN BEHIND THE FRONT. SNOW WILL TAPER OFF CHRISTMAS
AFTERNOON AS UPPER LEVEL SUPPORT SHIFTS SOUTHEAST. BUT LIGHT SNOW
COULD LINGER INTO FRIDAY MORNING IN MANY AREAS WITH LIGHT UPSLOPE
FLOW AND SLOW TO SHALLOW LOW LEVEL MOISTURE. WITH FRESH SNOW
COVER EXPECT COLD TEMPERATURES FOR FRIDAY MORNING. CHAMBERS


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

EXTENDED PERIOD LOOKS TO BE COLD AND SNOWY. MODELS OVERALL ARE IN
GOOD AGREEMENT LATE IN THE WEEK THROUGH THE UPCOMING WEEKEND. THE
STORM SYSTEM THAT WILL BE RESPONSIBLE FOR OUR CHRISTMAS SNOW IS
EXPECTED TO BE OUT OF THE AREA AND OUT INTO THE CENTRAL PLAINS BY
FRIDAY. THERE STILL WILL BE SOME LINGERING SNOW SHOWERS ALONG THE
WYOMING AND DAKOTA BORDERS SO WILL MAINTAIN A SLIGHT POP CHANCE
ACROSS OUR FAR SOUTH AND SOUTHEAST AREAS FOR FRIDAY.

FORECAST AREA WILL BE BETWEEN SYSTEMS BRIEFLY SATURDAY SO NOT
EXPECTING MUCH IN THE WAY OF SNOW SHOWER ACTIVITY. LEE-SIDE
TROUGHING SETS UP ONCE AGAIN BRINGING WINDY DOWNSLOPE CONDITIONS
TO THE AREA SATURDAY INTO SATURDAY NIGHT. HOWEVER...AN ARCTIC
FRONT APPROACHES LATE SATURDAY NIGHT WITH MODELS BRINGING IT
THROUGH BY LATE MORNING SUNDAY. TIMING DIFFERENCES DO EXIST THIS
FAR OUT BUT HAVE INTRODUCED A CHANCE FOR SNOW WITH THE FRONT LATE
IN THE DAY SATURDAY INTO SATURDAY NIGHT...BUT AS IT LOOKS
NOW...THE BEST CHANCES FOR SNOW LOOK TO ARRIVE SUNDAY ALONG AND
BEHIND THE FRONT.

TEMPERATURES WILL BE BELOW NORMAL THROUGHOUT THE ENTIRE EXTENDED
PERIOD WITH READINGS IN THE 20S FRIDAY THROUGH SUNDAY AND ONLY
TEENS FOR HIGHS MONDAY AND POSSIBLY TUESDAY. HOOLEY
&&

.AVIATION...

PARTLY CLOUDY SKIES WITH AN ISOLATED SNOW SHOWER CAN BE EXPECTED
FROM KBIL WESTWARD WITH VFR CONDITIONS PREVAILING. MVFR CEILINGS
WILL BE POSSIBLE THIS MORNING FOR THE KSHR AREA WITH VFR
CONDITIONS BY AFTERNOON. AREAS FURTHER EAST ALONG AND SOUTH OF A
KMLS-KBHK LINE CAN EXPECT SNOW SHOWERS ALONG WITH LOW CEILINGS AND
MVFR CONDITIONS THROUGH THIS MORNING WITH IMPROVING CONDITIONS
THIS AFTERNOON. HOOLEY/REIMER
&&

.PRELIMINARY POINT TEMP/POPS...

    TDY WED     THU     FRI     SAT     SUN     MON
-------------------------------------------------------
BIL 038 026/045 026/029 011/024 009/027 017/026 005/017
    0/U 01/E    ++/S    41/E    11/B    33/S    42/J
LVM 036 022/042 026/030 007/029 007/030 016/032 009/025
    1/N 02/R    ++/S    52/J    14/S    44/S    42/J
HDN 038 023/043 026/030 014/023 006/027 012/027 004/017
    0/B 02/R    ++/S    41/E    11/B    23/S    52/J
MLS 036 023/043 026/029 014/022 010/028 014/025 007/016
    1/B 12/R    76/S    21/E    11/B    23/S    32/J
4BQ 035 020/044 024/030 014/023 009/027 012/027 007/017
    2/J 10/B    68/S    42/J    11/B    13/S    32/J
BHK 031 018/040 023/028 011/018 008/025 012/023 004/013
    2/J 12/O    46/S    21/E    11/B    12/S    22/J
SHR 034 018/043 026/029 011/023 005/029 012/031 008/024
    1/B 00/B    ++/S    62/J    10/B    14/S    62/J

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO 6 PM MST
      WEDNESDAY FOR ZONES 65-66.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS



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