FXUS65 KMSO 070345
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
845 PM MST SUN DEC 6 2009
.UPDATE...HAVE UPGRADED WIND CHILL ADVISORIES FOR THE MISSOULA
VALLEY AND BITTERROOT/SAPPHIRE MOUNTAINS TO WIND CHILL WARNINGS.
ALSO ADJUSTED WIND SPEEDS...FORECAST LOW TEMPERATURES...CLOUD
COVER AND WIND CHILL READINGS.
&&
.DISCUSSION...ANOTHER SURGE OF BITTERLY AND DANGEROUSLY COLD
ARCTIC AIR HAS SPILLED OVER THE DIVIDE AND ARRIVED IN THE MISSOULA
VALLEY. THIS HAS RESULTED IN REPORTS OF SUSTAINED WINDS AROUND 20
MPH WITH GUSTS TO 30 MPH FUNNELING OUT OF HELLGATE CANYON.
SATELLITE IMAGERY HAS ALSO REVEALED THAT SKIES ARE FOR THE MOMENT
MOSTLY CLEAR ACROSS MUCH OF WEST CENTRAL MONTANA NEAR MISSOULA AND
OVER MUCH OF CENTRAL IDAHO. THIS HAS ALLOWED TEMPERATURES TO FALL
QUICKER THAN PREVIOUSLY FORECAST AND RESULTED IN WIND CHILL VALUES
APPROACHING IF NOT EXCEEDING WARNING CRITERIA. THUS HAVE UPGRADED
THE WIND CHILL ADVISORY FOR THE MISSOULA VALLEY TO A WIND CHILL
WARNING. WIND CHILL VALUES ARE EXPECTED TO REMAIN BETWEEN 15 AND
25 BELOW ZERO THROUGH MUCH OF THE NIGHT IN THE MISSOULA VALLEY
WITH LOCATIONS IN EAST MISSOULA AND DOWNTOWN MISSOULA...OR NEAR
HELLGATE CANYON SEEING THE COLDEST AND MOST DANGEROUS VALUES AT
TIMES APPROACHING 30 BELOW ZERO DURING THE OVERNIGHT HOURS.
ALTHOUGH WINDS WILL REMAIN GUSTY OVERNIGHT IN THE BITTERROOT
VALLEY AND TEMPERATURES FALLING BELOW ZERO BY MORNING...WIND CHILL
ADVISORY TYPE VALUES (10 TO 20 BELOW ZERO) CAN BE EXPECTED FROM
FLORENCE SOUTH.
ELSEWHERE HAVE DECIDED TO ISSUE A WIND CHILL ADVISORY FOR EASTERN LEMHI
COUNTY. LEADORE AND SALMON HAVE REMAINED GUSTY THROUGH THE EVENING
AND ARE LIKELY TO KEEP BREEZY WINDS GOING THROUGH AT LEAST DAWN.
MOSTLY CLEAR SKIES DOWN THERE HAVE ALSO RESULTED IN SOME LOCATIONS
COOLING QUICKER THAN PREVIOUSLY FORECAST AND THUS WIND CHILL
VALUES ARE IN SOME PLACES CURRENTLY AT ADVISORY LEVELS (LESS THAN
10 BELOW ZERO). FROM LEADORE SOUTH WIND CHILL READINGS MAY FALL
INTO THE WARNING CATEGORY (LOWER THAN 20 BELOW ZERO)...BUT BELIEVE
THIS WILL BE BRIEF AND WINDS SHOULD SUBSIDE BELOW 10 MPH BY THIS
TIME.
&&
.AVIATION...ANOTHER SURGE OF ARCTIC AIR WILL PUSH WEST OF THE DIVIDE
CREATING GUSTY WINDS AND MAY CAUSE SOME VISIBILITY ISSUES WITH ANY LINGERING
LOOSE SNOW. GUSTS TO 35 MPH ARE EXPECTED WITH THE INITIAL PUSH
THIS EVENING WITH SUSTAINED WINDS CONTINUING TO BE STRONG THROUGH
AT LEAST MONDAY MORNING.
&&
.PREV DISCUSSION... /ISSUED 253 PM MST SUN DEC 6 2009/
..DANGEROUS WIND CHILLS TO CONTINUE THROUGH MONDAY
MORNING...FOLLOWED BY SOME OF THE COLDEST TEMPERATURES THUS FAR OF
THE 2009-2010 WINTER SEASON...
DISCUSSION...THE ARCTIC AIR FELT PRESENTLY ACROSS THE REGION WILL
GET EVEN COLDER AS ANOTHER SURGE OF ARCTIC AIR PUSHES EAST OF THE
CONTINENTAL DIVIDE INTO WESTERN MONTANA AND CENTRAL IDAHO TONIGHT.
THIS SECOND SURGE WILL ONCE AGAIN INCREASE WINDS AND CAUSE
TEMPERATURES TO BECOME EVEN COLDER. THIS SECOND PUSH WILL RESULT
IN THE COLDEST WIND CHILLS TONIGHT THROUGH MONDAY MORNING. THOSE
DEPARTING FOR THE MORNING COMMUTE SHOULD TAKE PRECAUTION AS WIND
CHILLS WILL REACH DANGEROUS VALUES MONDAY MORNING THROUGH EARLY
MONDAY AFTERNOON. THE INCREASED PRESSURE GRADIENT WILL FINALLY BEGIN
TO RELAX LATER IN THE DAY MONDAY AS HIGH PRESSURE BUILDS IN. THIS
DECREASE IN WINDS WILL HELP IMPROVE WIND CHILLS TO MORE
MANAGEABLE VALUES...BUT AMBIENT AIR TEMPERATURES WILL QUICKLY COOL
TO VALUES SIMILAR TO THE WIND CHILL READINGS TONIGHT AND MONDAY.
TUESDAY MORNING IS STILL EXPECTED TO BE THE COLDEST MORNING FELT
YET BY WESTERN MONTANA...PARTICULARLY IN VALLEY LOCATIONS NEAR THE
DIVIDE. MINIMUM OVERNIGHT TEMPERATURES WILL FALL TO 20 TO 40 BELOW
ZERO (WITH NO ADDITIONAL INFLUENCE FROM WINDS AS THE GRADIENT
SHOULD REMAIN WEAK DURING THIS TIME). SOME CLOUD COVER MAY HANG
AROUND PORTIONS OF THE REGION UNTIL THE UPPER LOW MOVES FARTHER
EAST...BUT WILL NOT HELP MUCH IN KEEPING TEMPERATURES FROM FALLING
DRAMATICALLY THROUGHOUT THE NIGHT. WITH A VERY COLD START TUESDAY
MORNING...TUESDAY HIGH TEMPERATURES WILL STRUGGLE TO GET OUT
OF THE SINGLE DIGITS ABOVE ZERO.
TUESDAY NIGHT THROUGH FRIDAY THE MODELS ARE STILL IN GOOD
AGREEMENT THAT A PARENT LOW OVER CENTRAL CANADA WILL KEEP A
NORTHERLY UPPER LEVEL FLOW OVER THE INTER-MOUNTAIN REGION. THIS
FLOW WILL ALLOW WEAK WAVES OF ENERGY TO MOVE THROUGH NORTH CENTRAL
IDAHO AND WESTERN MONTANA. WITH COLD AIR IN PLACE...ONLY A
LITTLE BIT OF MOISTURE IS EXPECTED TO SPAWN LIGHT SNOW FROM THE
PASSING WAVES...BUT ACCUMULATIONS WILL BE LITTLE TO NONE.
TEMPERATURES ARE ALSO EXPECTED TO GRADUALLY WARM...BUT WILL REMAIN
BELOW SEASONAL VALUES THIS WEEK. BY NEXT WEEKEND...THE MODELS ARE
COMING IN LINE WITH A PACIFIC SYSTEM MOVING INTO THE INTER-
MOUNTAIN REGION. THERE ARE SOME TIMING AND TEMPERATURE
DIFFERENCES...BUT LOOKS LIKE MORE PRECIPITATION AND MODERATING
TEMPERATURES IS ON TAP FOR NEXT WEEKEND.
&&
.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 WARNING UNTIL 11 AM MST MONDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS-MISSOULA/BITTERROOT VALLEYS.
WIND CHILL ADVISORY UNTIL 11 AM MST MONDAY FOR KOOTENAI/CABINET
REGION-LOWER CLARK FORK REGION.
ID...WIND CHILL ADVISORY UNTIL 11 AM MST MONDAY FOR EASTERN LEMHI
COUNTY.
&&
$$
UPDATE...DICKERSON
PREVIOUS DISCUSSION...ALLEGRETTO/MEAD/DE ROSA
AVIATION...LOEFFELBEIN
