586
FXUS65 KMSO 181031
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
331 AM MST WED DEC 18 2024
DISCUSSION
- MIXED PRECIPITATION, INCLUDING FREEZING RAIN, OCCURRING IN
VALLEYS FROM MISSOULA NORTHWARD THIS MORNING.
- POTENTIALLY DAMAGING WINDS EXPECTED ACROSS WESTERN MONTANA THIS
AFTERNOON.
- HIGH PRESSURE BRING POTENTIAL FOR FOG AND LOW CLOUDS TO DEVELOP
THURSDAY INTO THE WEEKEND.
AN ATMOSPHERIC RIVER WILL CONTINUE TO IMPACT THE NORTHERN ROCKIES
THROUGHOUT THE DAY. WARM AIR ALOFT IS ADVANCING INTO THE REGION
FROM THE SOUTHWEST, CAUSING SNOW LEVELS TO RISE. LIGHT FREEZING
RAIN HAS BEEN REPORTED IN AREAS LIKE MISSOULA AND IS EXPECTED TO
SPREAD NORTHWARD INTO NORTHWEST MONTANA THROUGH THE EARLY MORNING
HOURS. SLICK ROADS, CAUSED BY SNOW TRANSITIONING TO RAIN, MAY
CREATE HAZARDOUS CONDITIONS FOR THE MORNING COMMUTE. KEEP IN MIND
THAT EVEN AREAS THAT SEE AIR TEMPERATURES SLIGHTLY ABOVE FREEZING
THIS MORNING MAY HAVE ICE FORM ON ROADWAYS DUE TO GROUND
TEMPERATURES AT OR BELOW FREEZING.
BY THIS AFTERNOON, SNOW LEVELS ARE FORECAST TO REACH 6,000 FEET
SOUTH OF I-90 AND 4,500 FEET IN NORTHWEST MONTANA, RESULTING IN A
CHANGEOVER TO RAIN FOR MOST VALLEY LOCATIONS. IN HIGHER
ELEVATIONS, HEAVY, WET SNOW REMAINS LIKELY. FORECAST MODELS
INDICATE A 70-80% CHANCE OF 6 INCHES OR MORE ACCUMULATING ABOVE
5,000 FEET IN NORTHWEST MONTANA BY 5 PM TODAY. ALONG HIGHWAY 2,
FROM WEST GLACIER TO MARIAS PASS, GUSTY WINDS UP TO 50 MPH ARE
EXPECTED, CREATING REDUCED VISIBILITY DUE TO BLOWING SNOW. A
WINTER STORM WARNING IS IN EFFECT FOR THESE AREAS.
A STRONG JET STREAM WILL ALSO BRING A SIGNIFICANT RISK OF GUSTY WESTERLY
WINDS ACROSS WESTERN MONTANA AND NORTH-CENTRAL IDAHO BY MIDDAY. THE
STRONGEST WINDS ARE EXPECTED ALONG THE CONTINENTAL DIVIDE AND ACROSS
WEST-CENTRAL AND SOUTHWEST MONTANA. VALLEYS ALONG AND EAST OF HIGHWAY 93
HAVE A 50-70% CHANCE OF EXPERIENCING WIDESPREAD GUSTS BETWEEN 45-55 MPH
DURING THE AFTERNOON AND EVENING. GUSTS EXCEEDING 60 MPH ARE 70-75% LIKELY
ALONG I-90 FROM DEERLODGE TO ANACONDA AND 20-30% LIKELY IN THE BITTERROOT
VALLEY. HIGH WIND WARNINGS ARE IN PLACE FROM 11 AM TO 11 PM. RESIDENTS
SHOULD SECURE LOOSE OUTDOOR ITEMS, AND TRAVELERS, PARTICULARLY THOSE IN
HIGH-PROFILE VEHICLES ON NORTH-SOUTH ROADS, SHOULD EXERCISE CAUTION.
LOOKING AHEAD, A RIDGE OF HIGH PRESSURE IS EXPECTED TO BUILD OVER THE
NORTHERN ROCKIES ON THURSDAY AND FRIDAY, INCREASING THE LIKELIHOOD OF FOG
AND LOW CLOUDS. WHILE MOST FORECAST MODELS SUGGEST THE RIDGE WILL PERSIST
INTO EARLY NEXT WEEK, SOME INDICATE THE POSSIBILITY OF WEAK SYSTEMS PASSING
THROUGH, BRINGING OCCASIONAL CLOUDS AND PRECIPITATION. ALTHOUGH FOG COULD
IMPACT HOLIDAY TRAVEL, CONFIDENCE REMAINS LOW FOR A WIDESPREAD FOG EVENT AT
THIS TIME.
AVIATION
AN ATMOSPHERIC RIVER WILL CONTINUE TO BRING WIDESPREAD
PRECIPITATION TO WESTERN MONTANA AND NORTH CENTRAL IDAHO TODAY,
CAUSING LOWERED CEILING AND VISIBILITY AND OBSCURATIONS OF THE
TERRAIN. A WARM NOSE OF AIR IN THE MID LEVELS HAS BEEN CAUSING
LOCALIZED AREAS OF FREEZING RAIN AROUND KMSO THIS MORNING. THIS
WARM AIR WILL WORK INTO NORTHWEST MONTANA, BRINGING FREEZING RAIN
AS FAR NORTH AS KGPI. OVERALL ACCUMULATIONS WILL BE LIGHT BUT
PAVED SURFACES MAY BE SLICK DUE TO COLD GROUND TEMPERATURES.
INCREASING SNOW LEVELS THROUGH THE MORNING WILL RESULT IN A
CHANGEOVER TO RAIN AT THE AREA TERMINALS. HIGH WINDS ARE LIKELY
THROUGHOUT THE NORTHERN ROCKIES ON BY THIS AFTERNOON. SOUTHERLY OR
SOUTHWESTERLY WINDS WILL INCREASE AND BECOME MOSTLY WESTERLY
AFTER ABOUT 18/1900Z. EXPECT GUSTS OF 40 TO 50 KNOTS IN THE
AFTERNOON AT ALL TERMINALS EXCEPT KSMN. AVIATORS SHOULD BE
PREPARED FOR EVEN STRONGER WINDS OVER THE MOUNTAIN CRESTS,
OBSCURED TERRAIN, AND LOW-LEVEL WIND SHEAR THROUGHOUT THE DAY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING FOR
BITTERROOT/SAPPHIRE MOUNTAINS...FLATHEAD/MISSION VALLEYS...
KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION...
POTOMAC/SEELEY LAKE REGION.
WIND ADVISORY FROM 11 AM THIS MORNING TO 11 PM MST THIS EVENING
FOR KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION.
WINTER STORM WARNING UNTIL 11 PM MST THIS EVENING FOR WEST
GLACIER REGION.
HIGH WIND WARNING FROM 11 AM THIS MORNING TO 11 PM MST THIS
EVENING FOR BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT
REGION...FLATHEAD/MISSION VALLEYS...MISSOULA/BITTERROOT
VALLEYS...POTOMAC/SEELEY LAKE REGION.
WINTER WEATHER ADVISORY UNTIL 9 AM MST THIS MORNING FOR
MISSOULA/BITTERROOT VALLEYS.
ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR
NORTHERN CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER
MOUNTAINS.
WIND ADVISORY FROM 11 AM MST /10 AM PST/ THIS MORNING TO 11 PM
MST /10 PM PST/ THIS EVENING FOR EASTERN LEMHI COUNTY...
SOUTHERN CLEARWATER MOUNTAINS...WESTERN LEMHI COUNTY.
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