607
FXUS65 KMSO 171829
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1129 AM MST MON FEB 17 2025
DISCUSSION
KEY MESSAGES:
- HEAVIER SNOWFALL, WINDS BLOWING AND DRIFTING SNOW, EXPECTED TO
CONTINUE THROUGH MONDAY NIGHT, SIGNIFICANTLY IMPACTING TRAVEL
ACROSS THE REGION.
- COLDER TEMPERATURES BY WEDNESDAY.
- ACTIVE WEATHER CONTINUES THROUGH THE WEEK AND INTO THE WEEKEND,
WITH SNOW LEVELS ABOVE VALLEY FLOORS AT TIMES THIS WEEKEND.
WIDESPREAD LIGHT SNOW DURING THE FIRST HALF OF THE DAY WILL START
TO TRANSITION TO HEAVIER SNOWFALL RATES BY MONDAY AFTERNOON AND
EVENING. AREAS OF WEST-TO-EAST ORIENTED SNOW BANDS ARE LIKELY TO
PRODUCE QUICKLY-ACCUMULATING SNOW AND LOCALIZED GUSTY WINDS.
AN ARCTIC BOUNDARY WILL CONTINUE TO SLOWLY CREEP WEST THROUGH THE
DAY AND INTO TUESDAY CONTINUING TO REINFORCE TEMPERATURES THAT
ARE COLD ENOUGH TO PRODUCE ALL-SNOW ACROSS THE ENTIRE REGION. AS
THIS BOUNDARY PUSHES THROUGH YOUR AREA, EXPECT DECREASING SNOWFALL
RATES AND DROPPING TEMPERATURES WITH GUSTY WINDS. GUSTY NORTH AND
EASTERLY WINDS UP TO 30 MPH (ESPECIALLY NEAR AND WITHIN MOUNTAIN
GAPS AND RIVER CANYONS) WILL CAUSE BLOWING AND DRIFTING OF
PREVIOUSLY-FALLEN SNOW PROLONGING REDUCED VISIBILITIES AND SLICK
ROADWAY CONDITIONS THROUGH LATE TUESDAY.
THE SOUTHWARD PROGRESSION OF THIS ARCTIC FRONT IS STILL A BIT
UNCERTAIN, MODELS ARE INDICATING ALMOST TOTAL CERTAINTY OF AN
ARCTIC FRONT BY TUESDAY MORNING AS FAR SOUTH AND WEST AS THE
MISSOULA VALLEY WITH PROBABILITIES TAPERING OFF TO ABOUT A 50%
CHANCE IN THE SOUTHERN BITTERROOT VALLEY AND EVEN LESS LIKELY AS
YOU HEAD FURTHER SOUTH AND WEST.
WITH SUFFICIENT POST-FRONTAL CLEARING SKIES, WEDNESDAY MORNING
WILL LIKELY BE QUITE COLD. THE COLDEST AIR WILL STAY EAST OF THE
DIVIDE BUT ON OUR SIDE, ALONG THE DIVIDE, MORNING LOWS COULD DROP
INTO THE SINGLE DIGITS BELOW ZERO. SINGLE DIGITS ARE EXPECTED WEST
OF THE DIVIDE TO MISSOULA, WITH TEENS SOUTH AND WEST OF MISSOULA.
THIS COLD AIR IS NOT EXPECTED TO SIGNIFICANTLY IMPACT NORTH-
CENTRAL ID WHICH WILL MERELY HAVE A SEASONALLY COLD START TO THE
DAY.
THE NEXT SYSTEM WILL BEGIN TO AFFECT OUR REGION WITH SNOW ON
WEDNESDAY AFTERNOON INTO THURSDAY. THIS SYSTEM WILL BE A BIT
MOISTURE-STARVED WITH UP TO AN INCH OF SNOW IN MOST VALLEYS AND 3
TO 6 INCHES IN THE HIGHEST TERRAIN OF THE CLEARWATER MOUNTAINS ID.
A COMBINATION OF A FLAT UPPER-LEVEL RIDGE, RISING 500MB HEIGHTS,
AND 30 TO 40KT MID LEVEL WINDS WILL CAUSE SNOW LEVELS TO RISE
ABOVE VALLEY FLOORS WITH LIGHT PRECIPITATION HEADING INTO THIS
WEEKEND. WE WILL CONTINUE TO MONITOR THIS STORM AS OVERNIGHT
TEMPERATURES MAY FALL BELOW FREEZING AND ALLOW FOR WET SURFACES TO
FREEZE UP.
AVIATION
AN ARCTIC BOUNDARY IS CURRENTLY POSITIONED ACROSS WESTERN
MONTANA, EXTENDING FROM KGPI SOUTHEASTWARD THROUGH MACDONALD PASS.
SURFACE OBSERVATIONS INDICATE COLDER TEMPERATURES ACCOMPANIED BY
EASTERLY TO NORTHEASTERLY WINDS. SATELLITE IMAGERY AND RADAR LOOPS
SHOW MOISTURE STREAMING INTO NORTH-CENTRAL IDAHO AND WESTERN
MONTANA FROM THE WEST AND NORTHWEST, CONTRIBUTING TO WIDESPREAD
LOW CEILINGS, REDUCED VISIBILITY, AND ENHANCED SNOWFALL ALONG THE
ARCTIC FRONT. THIS FRONT IS EXPECTED TO SHIFT SOUTHWESTWARD THIS
AFTERNOON AND EVENING. HIGH-RESOLUTION MODELS SUGGEST AN EXTENDED
BAND OF SNOW DEVELOPING ALONG THE FRONT, BRINGING PERIODS OF LOW
VISIBILITY AND HIGHER SNOWFALL RATES, PARTICULARLY NEAR AND ALONG
THE I-90 CORRIDOR. WIND PROFILES SOUTHWEST OF THE FRONT FAVOR THE
FORMATIONS OF ADDITIONAL SNOW BANDS STRETCHING FROM NORTH-CENTRAL
IDAHO TO WEST-CENTRAL MONTANA, LEADING TO INTERMITTENT PERIODS OF
ENHANCED SNOWFALL INTO TONIGHT.
BEHIND THE ARCTIC FRONT, GUSTY NORTH AND EAST WINDS WILL INCREASE
THE RISK OF BLOWING SNOW AND FURTHER REDUCED VISIBILITY. SNOW
COVERAGE IS EXPECTED TO GRADUALLY DECREASE FROM NORTH TO SOUTH BUT
IMPACTS WILL PERSIST IN NORTH-CENTRAL IDAHO, WEST-CENTRAL
MONTANA, AND LEMHI COUNTY THROUGH AT LEAST TUESDAY MORNING.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING UNTIL 9 AM MST TUESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT REGION...
LOWER CLARK FORK REGION...MISSOULA/BITTERROOT VALLEYS...
POTOMAC/SEELEY LAKE REGION.
WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING FOR
FLATHEAD/MISSION VALLEYS...WEST GLACIER REGION.
WINTER STORM WARNING FROM 11 AM THIS MORNING TO 9 AM MST TUESDAY
FOR FLATHEAD/MISSION VALLEYS...WEST GLACIER REGION.
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR
KOOTENAI/CABINET REGION.
ID...WINTER STORM WARNING UNTIL 8 AM PST TUESDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 10 AM PST MONDAY FOR LOWER HELLS
CANYON/SALMON RIVER REGION...OROFINO/GRANGEVILLE REGION.
WINTER STORM WARNING FROM 10 AM MONDAY TO 8 AM PST TUESDAY FOR
OROFINO/GRANGEVILLE REGION.
WINTER WEATHER ADVISORY UNTIL 9 AM MST TUESDAY FOR EASTERN LEMHI
COUNTY...WESTERN LEMHI COUNTY.
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