Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 011029
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
329 AM MST SUN FEB 1 2015

.SHORT TERM...VALID FOR TDY AND MON...

SHORTWAVE WHICH BROUGHT EVENING SNOWFALL TO SOUTHERN MONTANA HAS
SHIFTED INTO EXTREME SOUTHEAST MONTANA AND RADAR IS SHOWING A
DECREASING TREND IN THE CENTRAL ZONES. UPPER LEVEL RIDGING ALREADY
BUILDING INTO WESTERN MONTANA AND ASSOCIATED SUBSIDENCE OVER
CENTRAL MONTANA CAUSING DRYING EVIDENT IN WATER VAPOR IMAGERY.
HRRR SHOWING CHANCE FOR SNOW TO LINGER IN EXTREME SOUTHEAST
MONTANA FOR A FEW HOURS THIS MORNING BUT ACCUMULATING SNOW IS DONE
FOR THE EVENT.

MORNING ROADS WILL BE ICY BECAUSE INITIAL SNOWFALL MELTED AND
FROZE AND IT WILL BE A COLD START WITH TEMPERATURES MOSTLY AT 10
OR LESS EXCEPT FOR LIVINGSTON WHERE TEMPERATURES HAVE NOT COOLED
AS MUCH. EASTERLY WINDS THIS MORNING WILL TURN TO MORE OF A
DRAINAGE FLOW AS SURFACE HIGH PRESSURE RETREATS INTO THE DAKOTAS
AND CLEAR SKIES SHOULD ALLOW MODERATING TEMPERATURES. SHOULD BE
ENOUGH TO CAUSE ROADS TO THAW A BIT ACROSS THE WESTERN HALF OF THE
AREA WHERE SNOWFALL WAS LOCALLY HEAVIER.

NEXT ROUND OF ENERGY HEADING THROUGH CANADA TONIGHT WILL CAUSE
THE FLOW OVER WESTERN MONTANA TO BACK WHICH BRINGS A WARM FRONT
ACROSS THE AREA TONIGHT. THIS BRINGS A BETTER FLOW OF MOISTURE
INTO THE WESTERN ZONES AND THERE IS A CHANCE FOR SOME MOUNTAIN
SNOW. PLAINS COULD SEE SOME SNOW SHOWERS BUT DOWNSLOPE WILL BE
OFFSETTING MOST OF THE PRECIPITATION. TEMPERATURES WILL BE WARMER
OVERNIGHT. WINDS WILL INCREASE IN THE GAP FLOW AREAS BUT PRESSURE
GRADIENTS WILL NOT BE TOO STRONG AS THE ENERGY ALOFT KEEPS SURFACE
HIGH PRESSURE FROM DEVELOPING OVER WESTERN WYOMING AND EASTERN
IDAHO.

ON MONDAY COLD AIR BEGINS TO MOVE BACK INTO THE AREA BEHIND THE
WARM FRONT BUT STALLS OVER WESTERN PORTIONS OF SOUTHEAST MONTANA.
THIS KEEPS A DOWNSLOPE MODERATING FLOW OVER THE WESTERN HALF OF
THE AREA AND COLDER AIRMASS WITH SOME LIGHT SNOW OVER EASTERN
AREAS. SHOULD BE A TRANSITION ZONE ALONG THE WESTERN EDGE OF THE
PRECIPITATION SHIELD BUT WOULD EXPECT MORE OF A RAIN SNOW MIX AS
OPPOSED TO FREEZING RAIN BECAUSE OF SURFACE WINDS BEING WESTERLY.

LATEST GFS HOLDS THE DOWNSLOPE ZONE ACROSS THE CENTRAL AREAS
MONDAY NIGHT BUT THE ECMWF ALLOWS THE COLDER AIR TO DEEPEN WHICH
WOULD BRING THE SNOW BACK THROUGH CENTRAL AREAS INCLUDING BILLINGS
LATER MONDAY NIGHT. MADE NO CHANGES TO THIS PERIOD AS SUPPORT FOR
BOTH SOLUTIONS EVIDENT IN SREF GUIDANCE BUT LATEST RUN DOES SHOW A
STRONGER INCREASE PRECIPITATION COMPARED TO PREVIOUS RUNS. BORSUM
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...

MADE SEVERAL CHANGES TO THE EXTENDED FORECAST THIS MORNING...MOST
SIGNIFICANTLY IN THE FIRST COUPLE OF DAYS. THAT BEING SAID THE
OVERALL MESSAGE REMAINS THE SAME...WITH COOL AND UNSETTLED WEATHER
INTO MIDWEEK AND A WARM WEATHER THROUGH THE WEEKEND...WITH MID 50S
BY FRIDAY.

NORTHWEST FLOW ALOFT IS EXPECTED TO PERSIST OVER THE REGION ON
TUESDAY...AND A STRONG SHORTWAVE SLIDING THROUGH THE REGION
TUESDAY. THIS WAVE WILL BRING A REINFORCING SHOT OF COLD AIR INTO
THE REGION...ALTHOUGH MODELS APPEAR TO KEEP COLD AIR A BIT MORE
SHALLOW THAN IN EARLIER MODEL RUNS. OTHER THAN SLIGHTLY CHANGE IN
DEPTH OF COLD AIR...MODELS HAVE BEEN VERY CONSISTENT OVER THE PAST
FEW DAYS WITH THIS SYSTEM. DEVELOPING BAROCLINIC ZONE WILL IMPACT
NORTHERN AND EASTERN ZONES TUESDAY MORNING AND EARLY
AFTERNOON...AND PUSH WESTWARD TO IMPACT UPSLOPE AREAS IN THE
EVENING AND OVERNIGHT. RAISED POPS SIGNIFICANTLY FOR TUESDAY
THROUGH TUESDAY NIGHT...BASED ON MODEL CONSISTENCY. PRECIP APPEARS
TO TAPER OFF QUICKLY WEDNESDAY...BUT COLD AIRMASS WILL REMAIN IN
PLACE THROUGH THE DAY. THE ECMWF HAS BEEN CONSISTENTLY A BIT
SLOWER MOVING THE PRECIP OUT OF THE REGION...LINGERING QPF ACROSS
THE SOUTHERN TIER OF THE REGION THROUGH THE DAY WEDNESDAY.
LIKEWISE...THE GFS HAS BEEN CONSISTENT WITH FASTER MOVEMENT.
THEREFORE ADJUSTMENT WILL BE NEED IF THE ECMWF ENDS UP BEING CORRECT.

UPPER LEVEL RIDGING BEINGS TO TAKE OF THE PATTERN THURSDAY...AND
GENERALLY REMAINS IN CONTROL OVER THE REGION THROUGH THE REMAINDER
OF THE PERIOD. WEAK ENERGY...AND PACIFIC MOISTURE WILL CONTINUE TO
RIDE OVER THE RIDGE...KEEPING SOME SLIGHT POPS IN THE MOUNTAINS.
PERIODIC SHORTWAVES WILL FLATTEN RIDGE BY THURSDAY NIGHT...AND A
DEVELOPING LEESIDE SFC TROF WILL DEVELOP TO BRING POTENTIAL FOR
WINDY CONDITIONS TO LIVINGSTON AND NYE AREAS. FLATTENED FLOW WILL
ALSO LEAD TO RAPIDLY WARMING TEMPERATURES ACROSS THE WEST...WITH
DEVELOPING DOWNSLOPE FLOW THROUGH THE END OF THE WORK WEEK AND
INTO THE WEEKEND. A STRONGER PACIFIC WAVE WILL PUSH ACROSS THE
REGION SATURDAY...BUT WILL MAINLY BRING PRECIP WITH MOUNTAINS AND
EASTERN ZONES...AS DOWNSLOPE FLOW IN THE WEST SHOULD LIMIT ANY
PRECIP DEVELOPMENT. AAG


&&

.AVIATION...

LINGERING SNOW CONTINUES TO TAPER OFF ACROSS SOUTHEAST MONTANA
THIS MORNING...WITH MOST LOCATIONS RETURNING TO VFR FLIGHT
CONDITIONS...BUT SOME LOCALIZED MVFR CONDITIONS ARE POSSIBLE. MOSTLY
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE DAY AS SKIES
CLEAR. MORE SNOW AND REDUCED FLIGHT CONDITIONS CAN BE EXPECTED TO
BEGIN ACROSS THE REGION OVERNIGHT TONIGHT. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY MON     TUE     WED     THU     FRI     SAT
-------------------------------------------------------
BIL 031 028/047 027/031 013/031 026/045 036/053 038/056
    0/B 21/E    55/J    52/J    21/B    01/N    11/N
LVM 038 031/049 034/036 021/037 029/049 036/054 039/055
    0/B 31/N    44/W    43/W    21/E    11/N    21/N
HDN 030 022/043 022/029 008/030 018/043 030/051 030/054
    0/B 22/J    56/J    52/J    21/B    01/B    12/W
MLS 023 017/032 017/020 000/021 012/038 025/046 027/052
    0/B 24/J    67/J    30/B    11/B    11/B    12/W
4BQ 027 017/042 022/027 007/028 019/044 029/054 034/058
    1/B 23/W    57/J    41/B    11/B    01/B    12/W
BHK 019 013/031 015/017 000/018 012/036 025/045 028/050
    1/B 24/J    57/J    30/B    10/B    11/B    12/W
SHR 028 020/045 024/029 013/030 020/044 029/055 031/055
    0/B 21/E    22/J    52/J    11/B    00/B    12/W

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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