High Wind in Montana, January 25, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
451 AM MST WED JAN 25 2012

...FREEZING RAIN TO SIGNIFICANTLY IMPACT THE MORNING COMMUTE
THROUGHOUT MANY WESTERN MONTANA VALLEYS...

.DISCUSSION...A DISTINCT WARM FRONT HAS MOVED THROUGH THE NORTHERN
ROCKIES OVERNIGHT BRINGING AMPLE WARM AIR AND STEADILY INCREASING
WINDS TO THE REGION WHICH HAVE SUCCESSFULLY ERODED MANY OF THE
PREVIOUSLY ESTABLISHED VALLEY INVERSIONS. DESPITE THE WARMING AIR
TEMPERATURES...PAVED SURFACES REMAIN WELL BELOW FREEZING AND AS
SUCH THE TRANSITION IN PRECIPITATION FROM SNOW TO RAIN HAS
RESULTED ICE ACCUMULATION. VERY SLIPPERY AND HAZARDOUS CONDITIONS
WILL REMAIN THROUGHOUT THE MORNING FOR PERSONS WALKING OR DRIVING
AND THUS HAVE ISSUED A FREEZING RAIN ADVISORY FOR THE
MISSOULA/BITTERROOT VALLEYS. REMOTELY DETERMINING PRECIPITATION
TYPE IN THE POTOMAC/SEELEY LAKE REGION HAS BEEN MORE DIFFICULT
THIS MORNING WITH SOME AREAS PERHAPS FAVORING SNOWFALL OVER
FREEZING RAIN. HOWEVER OTHERS WILL BE SIGNIFICANTLY IMPACTED BY
FREEZING RAIN THIS MORNING. THUS HAVE ISSUED A WINTER WEATHER
ADVISORY FOR THE WINTRY MIX OF PRECIPITATION ANTICIPATED TO
CONTINUE THROUGH MUCH OF THE DAY. TRAVEL ALONG STATE HIGHWAYS
200...141 AND 87 COULD BE EXTREMELY CHALLENGING AT TIMES THIS
MORNING DUE TO LIGHT RAIN FALLING INTO VALLEYS WHERE VERY COLD
TEMPERATURES REMAIN. ELSEWHERE PREVIOUSLY ISSUED WINTER WEATHER
ADVISORIES WERE NOT CHANGED AS SNOW WILL CONTINUE TO FALL
THROUGHOUT THE MOUNTAINS WITH LOWER ELEVATIONS RECEIVING A WINTRY
MIX OF SNOW...RAIN AND FREEZING RAIN.

THE OTHER STORY FOR TODAY WILL BE VERY STRONG WINDS IN THE
MOUNTAINS AND AFFECTING SOME OF THE MORE WIND FAVORED VALLEYS OF
CENTRAL IDAHO AND WESTERN MONTANA. HAVE EXTENDED THE WIND ADVISORY
FOR GRANGEVILLE AND THE CAMAS PRAIRIE THROUGH THIS MID MORNING
WHEN MODELS SUGGEST A COLD FRONTAL PASSAGE WILL HELP INITIATE A
WIND SHIFT AND REDUCED THE AFFECTS WHICH PRODUCED GUSTS IN EXCESS
OF 50 MPH AT TIMES OVERNIGHT. HOWEVER DID MOVE UP THE START TIME
FOR THE WIND ADVISORY ACROSS THE BUTTE/BLACKFOOT REGION AS SOME
OBSERVING STATIONS ARE SHOWING WIND GUSTS TO 40 MPH. GUSTS IN
EXCESS OF 50 MPH AT TIMES ARE LIKELY THROUGH THIS
AFTERNOON...INCLUDING WITHIN THE CITY OF BUTTE.

VALLEY PRECIPITATION WILL GRADUALLY DECREASE THIS EVENING HOWEVER
THIS WILL NOT BE THE CASE IN THE MOUNTAINS AS STRONG FLOW ALOFT
WILL KEEP A STEADY FLOW OF MOISTURE ACROSS THE REGION. COLDER AIR
BEHIND THE FRONT WILL LOWER SNOW LEVELS BACK TO THE SURFACE OF
MANY VALLEYS TONIGHT. THIS WILL SET THE STAGE FOR ANOTHER WARM
FRONT/COLD FRONT PASSAGE ON THURSDAY. SNOW LEVELS DURING THE DAY
WILL RISE WHICH SHOULD KEEP MOST VALLEYS TO A RAIN/SNOW MIX OR
PERHAPS ALL RAIN DURING THE MORNING. FREEZING RAIN DOES NOT APPEAR
TO BE AN ISSUE BECAUSE THERE WON'T BE SUFFICIENT TIME OR CLEARING
TO REESTABLISH VALLEY COLD POOLS. HOWEVER PERSISTENT MOUNTAIN SNOW
RESULTING IN ANOTHER 5 TO 10 INCHES OF ACCUMULATION APPEAR LIKELY.
AS DOES THE POTENTIAL ISSUANCE OF ANOTHER SET OF WINTER WEATHER
ADVISORIES FOR THE PASSES. SHOWERY CONDITIONS BEHIND THE COLD
FRONT LATE THURSDAY AFTERNOON THROUGH THURSDAY NIGHT WILL LIKELY
RESULT IN SOME LIGHT VALLEY SNOW ACCUMULATIONS. THE MAIN EXCEPTION
WILL BE THE SEELEY LAKE/POTOMAC REGION WHERE COLD AIR SHOULD
REMAIN AND PRECIPITATION TYPE STAY ALL SNOW PRODUCING TOTAL
ACCUMULATION POTENTIALLY IN THE 4 TO 7 INCH RANGE.

EXTENDED...SATURDAY THROUGH TUESDAY...WESTERN MONTANA WILL BE
UNDER THE INFLUENCE OF HIGH PRESSURE FOR THE EARLY PART OF THE
WEEKEND. GLACIER PARK REGION AND EXTREME NORTHWEST MONTANA COULD
SEE A FEW SNOW SHOWERS WITH WESTERN MONTANA BEING ON THE EASTERN
AXIS OF HIGH PRESSURE AND THE INFLUENCE OF A NORTHWEST FLOW. MODELS
ARE STILL IN AGREEMENT WITH A STORM SYSTEM MOVING INTO THE
NORTHERN ROCKIES FOR THE START OF NEXT WEEK...ALTHOUGH IT IS STILL
TO EARLY TO NAIL DOWN THE PREDOMINATE PRECIPITATION TYPE FOR THE
VALLEYS. BUT THE MOUNTAINS CAN EXPECT ANOTHER ROUND OF SNOW.

&&

.AVIATION...A LARGE SHIELD OF PRECIPITATION IS STILL OVER WESTERN
MONTANA AND CENTRAL IDAHO...MOST OF THIS IS FALLING IN THE FORM OF
RAIN WITH ALL SNOW IN THE HIGHEST TERRAIN AND EXTREME NORTHWEST
MONTANA. POCKETS OF FREEZING RAIN WILL CONTINUE TO BE A CONCERN
FOR THE MISSOULA AND BITTERROOT VALLEY LOCATIONS INCLUDING KMSO UNTIL
25/1600Z.  ANOTHER CONCERN WILL BE THE GUSTY SOUTHEAST
WINDS...WHICH COULD GUST AS HIGH AS 30KTS FOR ALL AVIATION
SITES...WHICH WILL THEN TURN MORE WESTERLY THIS AFTERNOON. AVIATORS
CAN EXPECT TERRAIN OBSCURATION THROUGH WEDNESDAY MORNING AND INTO
THE EVENING AFTER THE PASSAGE OF THE COLD FRONT.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FLATHEAD/MISSION
     VALLEYS.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR MARIAS
     PASS.

     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY KOOTENAI/CABINET
     REGION.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR LOST
     TRAIL PASS.

     WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON BUTTE/BLACKFOOT
     REGION.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR I-90
     LOOKOUT PASS TO HAUGAN.

ID...WIND ADVISORY UNTIL 4 AM PST EARLY THIS MORNING FOR GRANGEVILLE
     AND VICINITY.

     WINTER WEATHER ADVISORY UNTIL 5 PM PST THIS AFTERNOON SOUTHERN
     CLEARWATER MOUNTAINS.

     WIND ADVISORY UNTIL 4 AM PST EARLY THIS MORNING LOWER HELLS
     CANYON/SALMON RIVER REGION.

     WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR LOST
     TRAIL PASS.

&&

SHORT TERM...DICKERSON
LONG TERM....ROBINSON
AVIATION...ROBINSON