414
FXUS65 KMSO 162136
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
236 PM MST TUE DEC 16 2025
DISCUSSION
KEY MESSAGES:
- ATMOSPHERIC RIVER IMPACTS: AN ATMOSPHERIC RIVER WILL BRING
WIDESPREAD RAIN AND HIGH-ELEVATION SNOW TODAY THROUGH WEDNESDAY
MORNING. SATURATED SOILS WILL LIKELY CAUSE RISES ON STREAMS AND
ROCKSLIDES IN STEEP TERRAIN, PARTICULARLY IN NORTHWEST MONTANA
AND NORTH-CENTRAL IDAHO.
- STRONG COLD FRONT WEDNESDAY: AN EXTREME COLD FRONT WILL SWEEP
ACROSS THE REGION ON WEDNESDAY. EXPECT A RAPID TRANSITION FROM
RAIN TO SNOW, AND DAMAGING WINDS WITH GUSTS OF 50-70 MPH IN
VALLEYS (HIGHER IN MOUNTAINS).
- WINTER CONDITIONS RETURN: FOLLOWING THE FRONT, COOLER AND
UNSETTLED WEATHER WILL PREVAIL FOR THE REMAINDER OF THE WEEK,
WITH SNOW LEVELS DROPPING TO VALLEY FLOORS AT TIMES AND PERIODS
OF MOUNTAIN SNOW AFFECTING TRAVEL.
THE ATMOSPHERIC RIVER CONTINUES TO STREAM INTO CLEARWATER COUNTY,
IDAHO, INTO WEST-CENTRAL MONTANA. THIS MOISTURE FEED WILL SHIFT
TO THE NORTH THIS EVENING, BRINGING 1 TO 2 INCHES OF ADDITIONAL
RAIN TO THE HIGHER TERRAIN ALONG THE MONTANA/IDAHO BORDER INTO THE
GLACIER NATIONAL PARK/BOB MARSHALL REGION BY WEDNESDAY MORNING.
THE MOUNTAINS IN LINCOLN COUNTY, MONTANA, COULD RECEIVE UP TO 3
INCHES. SNOW LEVELS DURING THIS EVENT WILL BE HOVERING BETWEEN
5,000 TO 6,000 FEET. GENERALLY, THE MOUNTAINS COULD GET UP TO A
FOOT OF NEW WET SNOW, WITH PEAKS ALONG THE CONTINENTAL DIVIDE
RECEIVING UP TO 24 INCHES.
AN EXTREMELY STRONG COLD FRONT WILL BE PUSHING THROUGH THE
NORTHERN ROCKIES BETWEEN 6 A.M. TO 10 A.M. WEDNESDAY MORNING.
SOUTHWESTERLY WINDS WILL BE STEADILY INCREASING IN INTENSITY AHEAD
OF THE FRONT DURING THE OVERNIGHT HOURS. BY EARLY MORNING, THE
MOUNTAINS COULD BE EXPERIENCING WIND GUSTS OVER 50 MPH. THESE
WINDS COULD MIX DOWN TO THE VALLEYS, ESPECIALLY ALONG HWY 95 SOUTH
OF COTTONWOOD, IDAHO, IN THE BITTERROOT VALLEY, AND PARTS OF THE
MISSION VALLEY OF MONTANA. THE FRONT WILL BRING EXTREME WINDS TO
THE REGION DURING THE MORNING HOURS. THE VAST MAJORITY OF THE
NORTHERN ROCKIES HAS A 60 TO 100 PERCENT CHANCE OF EXPERIENCING
WIND GUSTS GREATER THAN 50 MPH. THE BITTERROOT MOUNTAIN RANGE,
FLINT CREEK/ANACONDA RANGES, AND ALONG THE CONTINENTAL DIVIDE HAVE
A 50% CHANCE OF EXPERIENCING WIND GUSTS IN EXCESS OF 80 MPH.
THESE STRONGER WINDS HAVE THE POTENTIAL OF MIXING DOWN TO THE
VALLEYS, ESPECIALLY IN THE BITTERROOT VALLEY BETWEEN FLORENCE TO
CORVALLIS AND CHARLOS HEIGHTS TO CONNER, ALONG I-90 FROM DEER
LODGE TO ANACONDA, AND ALSO FROM GARRISON JUNCTION TO MACDONALD
PASS. THESE STRONG WINDS COULD CAUSE DAMAGE TO STRUCTURES,
WIDESPREAD DOWN TREES AND POWER OUTAGES, AND DANGEROUS DRIVING
CONDITIONS ON NORTH-TO-SOUTH ROADWAYS. ALL OF THE NORTHERN ROCKIES
IS UNDER AT LEAST A HIGH WIND WARNING LATE TONIGHT THROUGH
WEDNESDAY AFTERNOON. A WINTER STORM WARNING HAS BEEN ISSUED FOR
THE GLACIER NATIONAL PARK AREA FOR THE COMBINATION OF SNOW AND
WIND. THE WINDS WILL BEGIN TO SUBSIDE DURING THE AFTERNOON INTO
THE EVENING FROM WEST TO EAST.
THE NEXT PULSE OF INTENSE MOISTURE PUSHES THROUGH THE REGION
THURSDAY INTO FRIDAY. SNOW LEVELS WILL BE CONSIDERABLY LOWER
DURING THE ONSET OF PRECIPITATION, AROUND 3,000 FEET, AND STEADILY
RISE BY FRIDAY MORNING. THIS PUNCH OF MOISTURE WILL BRING ANOTHER
ROUND OF CONSIDERABLE SNOW TO THE HIGHER TERRAIN, ESPECIALLY
ACROSS NORTH-CENTRAL IDAHO INTO WEST-CENTRAL MONTANA. THE WINDS
ARE EXPECTED TO BE FAIRLY GUSTY WITH THIS SYSTEM, CAUSING
DOWNSLOPING EFFECTS IN THE VALLEYS. A WINTER STORM WATCH HAS BEEN
ISSUED FOR THE CLEARWATER, BITTERROOT, AND SAPPHIRE MOUNTAIN
RANGES FOR THE POTENTIAL IMPACTS TO THE MOUNTAIN PASSES.
THIS ACTIVE WEATHER PATTERN WILL PERSIST OVER THE NORTHERN ROCKIES
THROUGH THE REMAINDER OF THE FORECAST PERIOD AND POTENTIALLY INTO
THE BEGINNING OF THE NEW YEAR.
AVIATION
EXPECT WIND GUSTS OF ABOUT 20-30 KNOTS THIS AFTERNOON
OUT OF THE SOUTHWEST. WIND DIRECTION WILL SHIFT TO SOUTHERLY
AHEAD OF A POTENT COLD FRONT ARRIVING EARLY WEDNESDAY MORNING. LOW
LEVEL WIND SHEAR WILL CONTINUE ACROSS THE NORTHERN ROCKIES
AIRSPACE. IN ADDITION TO WIND IMPACTS, PRECIPITATION WILL REMAIN
IN THE FORM OF RAIN TODAY, RESULTING IN MINOR REDUCTIONS IN
VISIBILITY AND OBSCURED TERRAIN.
THE COLD FRONT ARRIVING OVERNIGHT TONIGHT THROUGH WEDNESDAY WILL
PRESENT SIGNIFICANT WIND IMPACTS ACROSS THE NORTHERN ROCKIES, AS
WELL AS HEAVY SNOW IN NORTHWEST MONTANA. SOUTH WINDS TRANSITION TO
WEST WINDS WITH THE FRONTAL PASSAGE. HIGH RESOLUTION GUIDANCE IS
SHOWING 70 KNOT GUSTS OUT OF THE WEST OVER MUCH OF THE NORTHERN
ROCKIES AIRSPACE BY ABOUT 17/1300Z.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH LATE FRIDAY
NIGHT FOR BITTERROOT/SAPPHIRE MOUNTAINS.
HIGH WIND WARNING FROM 2 AM TO 5 PM MST WEDNESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...FLATHEAD/MISSION VALLEYS...
KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION...
MISSOULA/BITTERROOT VALLEYS.
WINTER STORM WARNING FROM 8 PM THIS EVENING TO 11 PM MST
WEDNESDAY FOR WEST GLACIER REGION.
HIGH WIND WARNING FROM 2 AM TO 8 PM MST WEDNESDAY FOR
BUTTE/BLACKFOOT REGION...POTOMAC/SEELEY LAKE REGION.
ID...HIGH WIND WARNING FROM 2 AM MST /1 AM PST/ TO 2 PM MST /1 PM
PST/ WEDNESDAY FOR EASTERN LEMHI COUNTY...LOWER HELLS
CANYON/SALMON RIVER REGION...NORTHERN CLEARWATER
MOUNTAINS...OROFINO/GRANGEVILLE REGION...SOUTHERN
CLEARWATER MOUNTAINS...WESTERN LEMHI COUNTY.
WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH LATE FRIDAY
NIGHT FOR SOUTHERN CLEARWATER MOUNTAINS.
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