Winter Storm Watch 2, NWS Billings, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
314 AM MST TUE JAN 17 2012

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

VERY ACTIVE WEATHER PATTERN FOR THE REST OF THE WEEK. MANY THINGS
TO CONSIDER FROM WINDS AND BLOWING SNOW...TO FALLING TEMPERATURES
DURING THE DAY WEDNESDAY PRODUCING VERY LOW WIND CHILLS...TO A
POTENTIALLY SIGNIFICANT SNOW EVENT SETTING UP FOR WEDNESDAY
THROUGH THURSDAY. WILL START WITH WINDS FROM LIVINGSTON TO BIG
TIMBER.

LEE TROUGH WAS DEEPENING THIS MORNING...BUT HAS YET TO SET UP TO
THE DEGREE IT WILL BY LATE MORNING. THIS WILL BE A CONCERN
BECAUSE WILL LIKELY CAUSE ISSUES WITH BLOWING AND DRIFTING SNOW.
THE AREA FROM LIVINGSTON TO BIG TIMBER PICKED UP 2 TO 4 INCHES OF
NEW SNOW SUNDAY NIGHT AND MONDAY. THIS SNOW SHOULD BE EASILY
BLOWN AROUND AS SNOW IS LOOSE YET. WINDS HAVE ALREADY PICKED UP
AT LIVINGSTON WITH SUSTAINED WINDS TO 30 MPH AND GUSTS TO 35 MPH.
VISIBILITIES HAVE NOT BEEN RESTRICTED AT THE AIRPORT AS OF YET.
MODELS TIGHTEN UP THE LEE TROUGH A GREAT DEAL THIS MORNING AND
AFTERNOON WITH STRONG GAP FLOW EXPECTED. WINDS WILL BE STRONG
ENOUGH FOR AN ADVISORY. BELIEVE THERE WILL BE SOME RESTRICTION OF
VISIBILITY TO BLOWING SNOW...BUT NOT SURE HOW MUCH AS SNOW DEPTH
NOT TREMENDOUSLY DEEP. WILL ISSUE A BLOWING SNOW ADVISORY DUE TO
UNCERTAINTY OF HOW BLOWING SNOW WILL OCCUR AND MONITOR FOR A
POSSIBLE UPGRADE TO A BLIZZARD WARNING.

THE ARCTIC HAS LIFTED OFF THE SLOPES THIS MORNING AS LIVINGSTON
HAS TEMPERATURES RISING INTO THE TEENS AND BILLINGS WENT FROM
BELOW ZERO READINGS TO AROUND 10 WITH A SOUTHWEST WIND. WARMING
WILL BE LIMITED AS SOUTHWEST WINDS WILL BE BLOWING OVER FRESH
SNOW AND 850MB TEMPERATURES ARE NOT PROGGED THAT WARM TO BEGIN
WITH. THE ARCTIC BOUNDARY WILL GET PUSHED NORTH INTO NORTHERN
MONTANA TODAY. THE BOUNDARY WILL RETREAT TONIGHT FOR A RETURN
VISIT ON WEDNESDAY AND THIS TIME WILL INCLUDE AIR IN SOUTHERN
CANADA WHICH DID NOT MAKE IT THIS FAR DURING THE FIRST PUSH OF
COLDER AIR. THE FOCUS THEN BECOMES A POTENTIAL SIGNIFICANT SNOW
EVENT WEDNESDAY AND WEDNESDAY NIGHT.

AS MENTIONED ABOVE...THE ARCTIC BOUNDARY SURGES SOUTH THROUGH THE
AREA ON WEDNESDAY WITH 850MB TEMPERATURES OF -22C ENTERING
SOUTHERN MONTANA. HIGHS WILL BE IN THE MORNING WITH FALLING
READINGS THROUGH THE DAY. READINGS WILL LIKELY FALL TO AROUND
ZERO BY LATE AFTERNOON IN BILLINGS...WITH READINGS FALLING BELOW
ZERO IN THE EAST. WIND CHILLS WILL FALL WELL BELOW ZERO IN THE
AFTERNOON AS THE ARCTIC SETTLES IN. THE BOUNDARY WILL DEVELOP
UPSLOPE FLOW. THE AIRMASS WILL NOT BE AS UNSTABLE AS THE AIRMASS
OF SUNDAY NIGHT AND MONDAY BUT UPSLOPE WILL BE UP TO AROUND
800MB. DEEP MOISTURE WILL SPREAD OVER THE ARCTIC DOME AS MID
LEVEL HEIGHTS RISE. THE PATTERN LOOKS LIKE A STRONG MID LEVEL
WARM AIR ADVECTION SNOW PRODUCER.

THE GOOD DENDRITIC GROWTH ZONE IS PRETTY DEEP WITH STRONG WARM
AIR ADVECTION. WITH SUCH A COLD AIRMASS IN PLACE AND STRONG WARM
AIR ADVECTION ALOFT...SNOW RATES AND ACCUMULATIONS COULD BE
RATHER SIGNIFICANT FOR WEDNESDAY AND WEDNESDAY NIGHT. THERE WILL
BE A BAND OF HEAVY SNOW DEVELOP NEAR THE ARCTIC BOUNDARY AND
LOOKS TO BE OVER CENTRAL AND NORTHERN ZONES. THE MODELS WERE
HITTING THE MOUNTAINS AND THE WEST HARD TOO WITH THIS SYSTEM
THOUGH NOT SURE HOW MUCH SNOW WILL ACCUMULATE JUST NEAR THE
BOUNDARY NEAREST THE SLOPES. THE HEAVY SNOW BAND WILL PUSH NORTH
WEDNESDAY NIGHT AND WILL LIKELY SET UP FROM HARLOWTON TO JUST
NORTH OF BILLINGS TO HARDIN AND OVER THE LAME DEER. ACCUMULATIONS
COULD BE 6 TO 10 INCHES OVER NORTHERN LOCATIONS...WITH 4 TO 8
INCHES LIKELY IN BILLINGS. THE SNOW WILL TAPER OFF LATE THURSDAY
FROM BILLINGS SOUTH BUT LINGER OVER THE NORTH. WILL ISSUE A
WINTER STORM WATCH FOR WESTERN AND CENTRAL ZONES FOR THIS EVENT.
TWH

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

THE ACTIVE WINTER WEATHER PATTERN CONTINUES THROUGH THE EXTENDED
PERIOD. THE ARCTIC AIRMASS APPEARS TO BE DRAGGING ITS FEET AND
LINGERS IN THE REGION INTO EARLY FRIDAY. ADDITIONALLY...MOIST
PACIFIC FLOW LOOKS LIKE IT WILL PERSIST AT LEAST INTO EARLY NEXT
WEEK.

TREND TO KEEP ARCTIC AIR IN PLACE CONTINUES IN NEW MODEL RUNS.
HAVE COOLED TEMPS SLIGHTLY FOR BOTH THURSDAY AND FRIDAY. BUMPED
TEMPS UP SLIGHTLY THURSDAY IN THE NORTHERN ZONES WITH SLOWER
PROGRESSION OF ARCTIC AIR LIFTING OUT OF THE REGION. MULTIPLE
SHORTWAVES AND WEAKER COLD FRONTS CONTINUE ARE PROGGED THROUGH
THE REGION THROUGH THE EXTENDED PERIOD. BEST CHANCES FOR
SIGNIFICANT SNOW FOLLOWING THE ARCTIC WILL BE ON THE WESTERN
SLOPES AS OROGRAPHIC LIFT WILL COMBINE WITH MOISTURE AND
SHORTWAVES FOR SIGNIFICANT SNOW POTENTIAL IN THIS AREAS. SOME OF
THE STRONGER SHORTWAVES AND COLD FRONTS WILL GIVE AT LEAST A
SLIGHT CHANCES FOR PRECIP ACROSS MUCH OF THE REGION THROUGHOUT
THE EXTENDED PERIOD.

COOL SURFACE TEMPS ARE PROGGED TO BE ERODED AWAY BY ABOUT
SATURDAY...WITH HIGHS BACK IN THE 40S...WITH AN UPPER LEVEL RIDGE
MOVING OVER THE REGION. THE HITCH IS HOW MUCH SNOW WE STACK UP BY
THE BEGINNING OF THE EXTENDED PERIOD...AND HOW LONG IT STICKS
AROUND. DEEP SNOW COVER WOULD HINDER WARMUP. STRONG PACIFIC FLOW
OF WARM AIR...AND DOWNSLOPING IS BOUND TO HAVE IMPACT THROUGH
FRIDAY IN THE WEST PLAINS...AND MORE ON SATURDAY...BUT WILL HAVE
A BETTER IDEA AS WE GET CLOSER IN TIME. HAVE COOLED TEMPS
SLIGHTLY FOR SATURDAY...BUT MAINLY ALONG NORTHERN BORDER. AAG

&&

.AVIATION...

WEST TO SOUTHWEST WINDS OF 30 TO 40 KNOTS ARE EXPECTED TO
CONTINUE THROUGH TODAY FOR AREAS WEST OF KBIL. BLOWING SNOW
CAUSING REDUCED SFC VIS IS THE GREATEST CONCERN IN THESE
AREAS...ESPECIALLY IN BIG TIMBER AND KLVM. BLOWING SNOW MAY ALSO
CAUSE PERIODIC MOUNTAIN OBSCURATIONS THROUGH THE DAY.
OTHERWISE...MAINLY VFR CONDITIONS WILL PREVAIL ACROSS THE REGION
TODAY. SNOW SHOWERS WILL RETURN TO AREAS WEST OF KBIL AND IN THE
HIGH TERRAIN THIS EVENING...RESULTING IN REDUCED FLIGHT
CONDITIONS IN HEAVIER SNOW...AND MOUNTAIN OBSCURATION. SNOW WILL
SPREAD ACROSS THE REGION THROUGH WEDNESDAY MORNING. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY WED     THU     FRI     SAT     SUN     MON
-------------------------------------------------------
BIL 022 008/011 902/021 012/032 021/043 027/038 021/034
    0/N 28/S    86/S    42/S    33/W    22/W    22/J
LVM 022 008/016 006/037 028/038 027/041 025/035 021/033
    2/S 69/S    65/S    52/S    44/W    22/W    22/J
HDN 023 003/014 902/020 009/033 016/043 023/037 018/036
    0/B 28/S    87/S    52/S    33/W    22/J    22/J
MLS 020 902/003 908/014 002/022 014/035 022/033 016/032
    2/S 44/S    68/S    52/S    23/J    22/J    22/J
4BQ 022 004/014 905/021 005/028 017/044 023/038 021/036
    0/B 15/S    67/S    52/S    22/W    22/W    22/J
BHK 018 908/003 911/013 901/020 012/035 021/034 017/031
    2/S 33/S    48/S    52/S    23/J    22/J    23/J
SHR 022 006/020 004/029 014/037 022/044 023/038 021/034
    0/B 16/S    44/S    31/E    22/W    22/W    22/J

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH
      THURSDAY AFTERNOON FOR ZONES 28>30-34-35-38>42-56>58-63>68.
     WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 PM MST THIS
      AFTERNOON FOR ZONES 41-64>66.
WY...NONE.

&&

WEATHER.GOV/BILLINGS

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