FXUS65 KMSO 060350
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
850 PM MST SAT DEC 5 2009
.UPDATE...HAVE UPDATED WIND SPEED AND DIRECTION...WIND CHILL
READINGS AND TEMPERATURES.
&&
.DISCUSSION...SINGLE DIGIT DEW POINT TEMPERATURES AND EAST TO
NORTHEAST WINDS REVEAL THAT THE MODIFIED ARCTIC AIR-MASS HAS
SPILLED OVER THE DIVIDE AND FUNNELED THROUGH THE MOUNTAIN VALLEYS
INTO THE MISSOULA...BITTERROOT AND FLATHEAD VALLEYS. BUT THIS IS
ONLY THE BEGINNING OF THE EXTREMELY COLD WEATHER. 00Z SOUNDINGS
FROM GREAT FALLS AND EDMONTON...ALBERTA SHOW THAT THE COLDEST
ARCTIC AIR HAS YET TO SPILL OVER THE DIVIDE OR EVEN CROSS THE
CANADIAN BORDER FOR THAT MATTER. THIS BODES WELL FOR THE EXTREME
TEMPERATURES CURRENTLY FORECAST FOR TOMORROW THROUGH TUESDAY AND
WIND CHILL HIGHLIGHTS IN EFFECT. THUS HAVE MADE MINOR CHANGES TO
ADJUST THE TIMING AND STRENGTH OF WIND SPEEDS BASED ON CURRENT
OBSERVATIONS AS WELL AS FORECAST TEMPERATURES FROM RECENT DEW
POINT TRENDS AS THE FIRST BIT OF ARCTIC AIR MAKES ITS WAY INTO
WESTERN MONTANA.
THE COLD AIR-MASS HAS ALSO SHOWN TO BE A LITTLE BIT DEEPER THAN
PREVIOUSLY FORECAST...SPILLING OVER INTO LEMHI COUNTY...IDAHO.
STRONG AND GUSTY WINDS DEVELOPED EARLIER ALONG THE FRONT AND WILL
REMAIN ABOVE 10 MPH THROUGH THE NIGHT AND MUCH OF TOMORROW. WITH
FALLING TEMPERATURES FORECAST...WIND CHILL READINGS OF -10 TO -20
DEGREES CAN BE EXPECTED AND THUS HAVE ISSUED A WIND CHILL
ADVISORY.
&&
.AVIATION...THE ARCTIC COLD FRONT WILL MOVE THROUGH WESTERN MONTANA
TONIGHT...AND NORTH CENTRAL IDAHO SUNDAY. SNOW IS CONFINED TO THE
CONTINENTAL DIVIDE AND THIS WILL CONTINUE THROUGH SUNDAY. WINDS
WILL INCREASE FROM THE NORTH/NORTHEAST THIS EVENING AND CONTINUE TONIGHT.
THE STRONGEST WINDS ARE EXPECTED AT KGPI AND KMSO. KGPI MAY ALSO
EXPERIENCE SOME REDUCTIONS TO VISIBILITIES FROM BLOWING SNOW WITH
THE INITIAL PUSH...BUT THIS IS ONLY EXPECTED TO LAST A FEW HOURS.
BREEZY AND COLD WITH IMPROVING CEILINGS WILL BE THE STORY FOR
SUNDAY...EXCEPT ALONG THE CONTINENTAL DIVIDE.
&&
.PREV DISCUSSION... /ISSUED 504 PM MST SAT DEC 5 2009/
UPDATE...HAVE ALLOWED THE WINTER WEATHER ADVISORY FOR THE GLACIER
NATIONAL PARK AREA TO EXPIRE AT 5 PM.
DISCUSSION...JUST DOING A QUICK UPDATE TO ALLOW THE WINTER
WEATHER ADVISORY FOR THE GLACIER NATIONAL PARK AREA TO EXPIRE AT 5
PM MST. AN ADDITIONAL UPDATE IS PLANNED IN THE NEXT HOUR OR SO TO
INCREASE WINDS SPEEDS...MAKE SOME MINOR ADJUSTMENTS TO
TEMPERATURES AND WIND CHILL READINGS.
PREV DISCUSSION... /ISSUED 214 PM MST SAT DEC 5 2009/
.ARCTIC AIR...STRONG WINDS...AND DANGEROUS WIND CHILLS EXPECTED
TO BEGIN TONIGHT AND CONTINUE THROUGH MONDAY...
DISCUSSION...SNOW SHOWERS WILL CONTINUE TO FALL FOR THE REST OF
THE EVENING BUT REMAIN CONFINED TO AREAS ALONG THE CONTINENTAL
DIVIDE. THE ARCTIC FRONT WILL THEN MAKE ITS WAY INTO THE REGION
SOMETIME LATER THIS EVENING...EXPECTED FIRST TO PUSH THROUGH
NORTHWEST MONTANA AND THEN THROUGH WEST CENTRAL MONTANA AND
CENTRAL IDAHO AFTER MIDNIGHT. WINDS HAVE ALREADY BEGUN TO PICK UP
IN EXTREME NORTHWEST MONTANA AND WILL CONTINUE TO INCREASE AS THE
DEEP POOL OF ARCTIC AIR SPILLS ACROSS THE DIVIDE. THE ARCTIC FRONT
WILL CAUSE ANY NEWLY FALLEN FLUFFY SNOW TO BE BLOWN ABOUT DUE TO
AN INCREASE IN WINDS ASSOCIATED WITH THE FRONTAL PUSH. THIS WILL
BE FELT MOST ALONG THE MONTANA HIGHWAY 93 CORRIDOR BETWEEN EVARO
AND POLSON...WHERE SNOWFALL AMOUNTS WERE GREATEST FROM LAST NIGHTS
SYSTEM. AS A RESULT...PERIODS OF REDUCED VISIBILITIES CAN BE
EXPECTED WITH THE FRONT DUE TO THE BLOWING SNOW. A WINTER WEATHER
ADVISORY FOR BLOWING SNOW HAS BEEN ISSUED FOR THIS SPECIFIC AREA.
THE UPPER LEVEL LOW WILL SAG FURTHER SOUTH OVERNIGHT AND ALLOW
THE VERY COLD ARCTIC AIR MASS TO FINALLY SETTLE IN ACROSS THE
NORTHERN ROCKIES. WINDS ARE ARE NOT ANTICIPATED TO RELAX MUCH AFTER
THE ARCTIC FRONT PASSES SINCE A TIGHT PRESSURE GRADIENT WILL
REMAIN FIRM AND HELP WINDS TO STAY BREEZY THROUGH THE NIGHT AND
ALL DAY SUNDAY. NO REAL DAYTIME HEATING WILL BE EXPERIENCED AS
EVEN COLDER AIR WILL CONTINUE TO SETTLE IN AS THE DAY CONTINUES.
WINDS ARE STILL EXPECTED TO REMAIN FAIRLY STRONG...WHICH WILL
RESULT IN VERY DANGEROUS WIND CHILLS THROUGH MONDAY MORNING.
MONDAY NIGHT THROUGH TUESDAY NIGHT...WITH COLD AIR SUFFICIENTLY
POOLED IN VALLEYS ACROSS THE REGION...TEMPERATURES WILL CONTINUE
TO BE 30 DEGREES BELOW SEASONAL NORMALS.
WEDNESDAY THROUGH SATURDAY...MEDIUM AND LONG RANGE MODELS CONTINUE
TO INDICATE A BROAD TROUGH OVER WESTERN PROVINCES OF CANADA
PROVIDING A NORTHERLY FLOW OVER THE NORTHERN ROCKIES THROUGH THE
REMAINDER OF THE WEEK. GIVEN THE DRY ARCTIC AIR MASS...THIS MEANS
THAT SNOW RATIOS SHOULD BE HIGH WITH LITTLE TO NO ACCUMULATIONS
EXPECTED WITH EACH PASSING SHORTWAVE FEATURE CAUGHT UP IN THE
FLOW. TEMPERATURES THROUGH THIS TIME WILL BE SLOW TO WARM UNDER
NORTHWEST FLOW AND RELATIVELY CALM WINDS.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WIND CHILL WARNING UNTIL 11 AM MST MONDAY FOR BUTTE/BLACKFOOT
REGION-FLATHEAD/MISSION VALLEYS-POTOMAC/SEELEY LAKE REGION-
WEST GLACIER REGION.
WIND CHILL ADVISORY UNTIL 11 AM MST MONDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS-KOOTENAI/CABINET REGION-LOWER
CLARK FORK REGION-MISSOULA/BITTERROOT VALLEYS.
WINTER WEATHER ADVISORY UNTIL 2 AM MST SUNDAY FOR
FLATHEAD/MISSION VALLEYS.
ID...WIND CHILL ADVISORY FROM 5 AM TO 5 PM MST SUNDAY FOR WESTERN
LEMHI COUNTY.
WIND CHILL ADVISORY UNTIL 5 PM MST SUNDAY FOR EASTERN LEMHI
COUNTY.
&&
$$
UPDATE...DICKERSON
PREVIOUS DISCUSSION....ALLEGRETTO/MEAD/DE ROSA
AVIATION...LOEFFELBEIN
