FXUS65 KMSO 060004
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
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.
&&
.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 STARTING
IN KGPI AROUND 06/03Z...KMSO AROUND 06/08Z...KBTM 06/09Z...KSMN
06/12Z. 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 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 FROM 8 PM THIS EVENING TO 11 AM MST MONDAY
FOR BUTTE/BLACKFOOT REGION-FLATHEAD/MISSION VALLEYS-
POTOMAC/SEELEY LAKE REGION-WEST GLACIER REGION.
WIND CHILL ADVISORY FROM 8 PM THIS EVENING TO 11 AM MST MONDAY
FOR BITTERROOT/SAPPHIRE MOUNTAINS-KOOTENAI/CABINET REGION-
LOWER CLARK FORK REGION-MISSOULA/BITTERROOT VALLEYS.
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 2 AM MST
SUNDAY FOR FLATHEAD/MISSION VALLEYS.
ID...NONE.
&&
$$
UPDATE...DICKERSON
PREVIOUS DISCUSSION...ALLEGRETTO/MEAD/DE ROSA
AVIATION...LOEFFELBEIN
