149
FXUS65 KMSO 121911
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
111 PM MDT SUN OCT 12 2025
DISCUSSION
KEY MESSAGES:
- WINTER TRAVEL IMPACTS OVER MOUNTAIN PASSES THIS AFTERNOON WILL
TRANSITION INTO THE VALLEYS OF NORTHWEST MONTANA THIS EVENING
INTO MONDAY MORNING.
- DAMAGING NORTHEAST WINDS GUSTING 40-50 MPH IN NORTHWEST MONTANA
TONIGHT INTO MONDAY THREATEN TO CAUSE POWER OUTAGES AND FALLING
TREES, A RISK AMPLIFIED BY HEAVY SNOW ON LEAFY BRANCHES AND
UNFROZEN GROUND.
AN ARCTIC COLD FRONT CONTINUES TO PUSH ACROSS THE CONTINENTAL
DIVIDE, BRINGING GUSTY NORTH TO EAST WINDS TO NORTHWEST MONTANA
THIS AFTERNOON. THIS ARCTIC AIRMASS WILL SURGE SOUTH AND WEST THIS
EVENING, ENCOMPASSING WEST-CENTRAL MONTANA AND NORTH-CENTRAL
IDAHO OVERNIGHT. SNOW LEVELS WILL SUBSEQUENTLY FALL, REACHING MOST
WESTERN MONTANA VALLEY FLOORS AND THE HIGHER VALLEYS OF NORTH-
CENTRAL IDAHO LATE TONIGHT. BY MONDAY MORNING, PRECIPITATION IS
EXPECTED TO BE ALL SNOW ACROSS WESTERN MONTANA AND NORTH CENTRAL
IDAHO, WITH THE EXCEPTION OF THE LOWEST IDAHO VALLEYS.
THE MOST SIGNIFICANT IMPACTS FROM SNOW ARE EXPECTED FROM TONIGHT
THROUGH MONDAY MORNING, PRIMARILY AFFECTING NORTHWEST MONTANA AND
AREAS ALONG THE CONTINENTAL DIVIDE. A PERIOD OF STEADY,
ACCUMULATING SNOW WILL CREATE HAZARDOUS WINTER TRAVEL CONDITIONS,
ESPECIALLY FOR MOUNTAIN PASSES. WHILE CONFIDENCE IN VALLEY SNOW
TOTALS REMAINS LOW DUE TO MODEL VARIABILITY AND WARM GROUND
TEMPERATURES, THE COMBINATION OF SNOW, GUSTY WINDS, AND FREEZING
TEMPERATURES WILL CREATE A SIGNIFICANT RISK FOR ICY ROAD
CONDITIONS. HIGH-RESOLUTION GUIDANCE HIGHLIGHTS THE HIGHWAY 2
CORRIDOR BETWEEN LIBBY AND KILA AS A ZONE OF PARTICULAR CONCERN
FOR INTENSE SNOWFALL AND ICING BETWEEN 6 PM AND MIDNIGHT TONIGHT,
WHERE THE ARCTIC BOUNDARY AND INCOMING MOISTURE WILL INTERACT.
SNOW SHOWERS WILL DECREASE IN INTENSITY THROUGH THE DAY MONDAY.
STRONG NORTHEASTERLY WINDS WILL DEVELOP OVERNIGHT AND CONTINUE
INTO MONDAY. GUSTS OF 40 TO 50 MPH ARE EXPECTED, PARTICULARLY
THROUGH CHANNELED TERRAIN SUCH AS THE EASTERN FLATHEAD VALLEY,
FLATHEAD LAKE AND ACROSS THE MOUNTAINS. THESE WINDS COULD LEAD TO
POWER OUTAGES, DOWNED TREES, AND DOCK DAMAGE ALONG THE WESTERN
SHORES OF FLATHEAD LAKE. THE COMBINATION OF WIND AND COLD WILL
ALSO PRODUCE WIND CHILLS IN THE TEENS AND 20S BY MONDAY MORNING.
WIND MAY FURTHER STRESS TREES THAT HAVE ACCUMULATED SNOWFALL THIS
EVENING, POSSIBLY BREAKING BRANCHES AND CAUSING ISOLATED POWER
OUTAGES.
UNCERTAINTY REMAINS REGARDING A POTENTIAL BAND OF PRECIPITATION
DEVELOPING LATE TONIGHT AND MOVING NORTH THROUGH THE BITTERROOT
AND MISSOULA VALLEYS DURING MONDAY MORNING'S COMMUTE. WHILE ONLY
DEPICTED IN SOME HIGH-RESOLUTION MODELS, ITS DEVELOPMENT WOULD
INTRODUCE A RISK OF SLICK TRAVEL CONDITIONS THAT IS NOT FULLY
REFLECTED IN THE CURRENT FORECAST. THIS IS A KEY FEATURE TO
MONITOR OVERNIGHT.
LOOKING AHEAD, MODELS SUGGEST ANOTHER ROUND OF LIGHT SNOW IS
POSSIBLE TUESDAY MORNING, WHICH COULD AGAIN IMPACT TRAVEL,
ESPECIALLY IN THE SOUTHERN BITTERROOT VALLEY, LEMHI COUNTY, AND
SOUTHWEST MONTANA PASSES. THE COLD AIRMASS WILL SLOWLY MODERATE
FROM TUESDAY ONWARD, THOUGH TEMPERATURES WILL REMAIN BELOW
AVERAGE FOR MID-OCTOBER. THE PATTERN REMAINS UNSETTLED, WITH
MODEL GUIDANCE INDICATING A POTENTIAL YELLOWSTONE LOW DEVELOPING
WEDNESDAY INTO THURSDAY, BRINGING ANOTHER CHANCE FOR HIGH-
ELEVATION SNOW TO SOUTHWEST MONTANA.
AVIATION
AN ARCTIC FRONT WILL CREATE DETERIORATING AVIATION
CONDITIONS ACROSS WESTERN MONTANA AND NORTH CENTRAL IDAHO FROM
THIS EVENING THROUGH MONDAY. WIDESPREAD IFR/MVFR CONDITIONS ARE
EXPECTED DUE TO A PERIOD OF STEADY SNOW, ESPECIALLY ACROSS
NORTHWEST MONTANA AND ALONG THE CONTINENTAL DIVIDE. AS SNOW LEVELS
FALL OVERNIGHT, A SIGNIFICANT THREAT OF MODERATE RIME ICING WILL
DEVELOP IN THE FLIGHT LEVELS BELOW 10,000 FT MSL. FURTHERMORE,
STRONG NORTHEASTERLY SURFACE WINDS GUSTING 40 TO 50 MPH WILL
CREATE HAZARDOUS CROSSWINDS FOR TERMINAL OPERATIONS AND GENERATE
SIGNIFICANT LOW-LEVEL TURBULENCE, PARTICULARLY THROUGH CHANNELED
TERRAIN LIKE THE FLATHEAD VALLEY AND NEAR MOUNTAIN PASSES.
CONDITIONS ARE EXPECTED TO GRADUALLY IMPROVE MONDAY AFTERNOON AS
SNOW INTENSITY AND COVERAGE DECREASE.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL NOON MDT MONDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT REGION...
LOWER CLARK FORK REGION...POTOMAC/SEELEY LAKE REGION.
WINTER STORM WARNING UNTIL NOON MDT MONDAY FOR KOOTENAI/CABINET
REGION...WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON MDT
MONDAY FOR FLATHEAD/MISSION VALLEYS.
HIGH WIND WARNING FROM 9 PM THIS EVENING TO NOON MDT MONDAY FOR
FLATHEAD/MISSION VALLEYS.
ID...WINTER WEATHER ADVISORY UNTIL 11 AM PDT MONDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 6 AM MDT MONDAY FOR EASTERN LEMHI
COUNTY...WESTERN LEMHI COUNTY.
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