609
FXUS65 KMSO 120837
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
237 AM MDT SUN OCT 12 2025
DISCUSSION
KEY MESSAGES:
- RAIN WILL TRANSITION TO SNOW TODAY ACROSS NORTHWEST MONTANA.
- WINTER TRAVEL IMPACTS ARE EXPECTED OVER MOUNTAIN PASSES TODAY,
AND AS SNOW LEVELS FALL TO VALLEY FLOORS, WIDESPREAD TRAVEL
IMPACTS ARE EXPECTED FOR THE MONDAY MORNING COMMUTE.
- 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.
THE LATEST MODEL GUIDANCE CONTINUES TO SUPPORT A TRANSITION TO
WINTER-LIKE WEATHER TODAY. THE MAIN FOCUS IS THE CHANGEOVER FROM
RAIN TO SNOW, WHICH WILL PROGRESS FROM NORTH TO SOUTH ACROSS THE
REGION.
FOR NORTHWEST MONTANA, THIS TRANSITION IS IMMINENT THIS MORNING.
GUSTY NORTH TO EAST WINDS WILL ALSO DEVELOP IN THE FLATHEAD
VALLEY, ADDING TO THE RAW FEEL. FOR WEST-CENTRAL MONTANA AND
NORTH-CENTRAL IDAHO, SNOW LEVELS WILL FALL TO HIGHER VALLEYS IN
IDAHO AND MOST VALLEY FLOORS OF WESTERN MONTANA THIS EVENING
THROUGH TONIGHT. BY MONDAY MORNING, ALL PRECIPITATION ACROSS THE
FORECAST AREA WILL BE IN THE FORM OF SNOW, EXCEPT FOR THE LOW
VALLEYS OF IDAHO.
THE MOST WIDESPREAD AND SIGNIFICANT IMPACTS ARE EXPECTED FROM
TONIGHT THROUGH MONDAY MORNING. A PERIOD OF STEADIER, ACCUMULATING
SNOW WILL CREATE WINTER TRAVEL CONDITIONS IN THE HIGH TERRAIN AND
OVER MOUNTAIN PASSES. SNOW WILL ALSO FALL IN VALLEY LOCATIONS,
WHICH STILL HAVE A WIDE RANGE FOR SNOW AMOUNTS. SNOW, ALONG WITH
WIND, AND BELOW FREEZING TEMPERATURES INCREASES THE RISK FOR ICY
CONDITIONS. SNOW SHOWERS WILL LINGER THROUGH THE DAY ON MONDAY,
BUT THE INTENSITY IS EXPECTED TO DECREASE BY THE AFTERNOON.
WINDS WILL ALSO INCREASE AND BECOME GUSTY ACROSS THE ENTIRE
REGION OVERNIGHT INTO MONDAY. NORTHEASTERLY WIND GUST OF 40 TO 50
MPH ARE EXPECTED, ESPECIALLY THROUGH CHANNELED TERRAIN IN THE
EASTERN FLATHEAD VALLEY, SOUTHEASTERN PORTIONS OF FLATHEAD LAKE
AND THROUGH THE MOUNTAINOUS TERRAIN. KEY IMPACTS INCLUDE THE
POTENTIAL FOR POWER OUTAGES, FALLING TREES, AND DOCK DAMAGE ALONG
THE SOUTHERN SHORES OF FLATHEAD LAKE. THE WINDS WILL ALSO DRIVE
MORNING WIND CHILLS DOWN INTO THE TEENS AND 20S.
MODEL GUIDANCE ARE TRENDING TOWARD ANOTHER ROUND OF LIGHT SNOW
TUESDAY MORNING, WHICH MAY CAUSE TRAVEL IMPACTS. THE COLD AIRMASS
WILL SLOWLY BEGIN TO MODERATE FROM TUESDAY ONWARD, BUT
TEMPERATURES WILL REMAIN BELOW AVERAGE FOR MID- OCTOBER. THE
WEATHER PATTERN LOOKS TO REMAIN UNSETTLED WITH ADDITIONAL CHANCES
FOR SHOWERS LATER IN THE WEEK.
AVIATION
WIDESPREAD DETERIORATION TO MVFR AND IFR IS EXPECTED
TODAY AS A SYSTEM BRINGS LOW CEILINGS, RAIN, AND SNOW TO NORTH-
CENTRAL IDAHO AND WESTERN MONTANA. THESE CONDITIONS WILL LIKELY
PERSIST THROUGH MONDAY MORNING. THE RAIN-TO-SNOW CHANGEOVER FOR
NORTHWEST MONTANA VALLEYS, INCLUDING AT KALISPELL (KGPI), REMAINS
ON TRACK FOR THIS MORNING.
A SIGNIFICANT WIND CONTRAST WILL DEVELOP ALONG THE I-90 CORRIDOR:
- SOUTH AND WEST OF I-90: WESTERLY WINDS WILL DOMINATE.
- NORTH OF I-90: EASTERLY WINDS WILL USHER IN COOLER AIR, CAUSING
SNOW LEVELS TO FALL.
TONIGHT, THIS EASTERLY FLOW WILL EXPAND ACROSS THE ENTIRE REGION,
LEADING TO DROPPING SNOW LEVELS THROUGHOUT WESTERN MONTANA AND
NORTH-CENTRAL IDAHO. BY MONDAY MORNING, THE EASTERLY WINDS WILL
BECOME STRONG AND GUSTY, ESPECIALLY OVER HIGH TERRAIN AND NEAR
FLATHEAD LAKE. PILOTS SHOULD ANTICIPATE SIGNIFICANT MECHANICAL
TURBULENCE AND THE POTENTIAL FOR LOW-LEVEL WIND SHEAR. IFR
CONDITIONS ARE EXPECTED TO PERSIST THROUGH MUCH OF THE MORNING.
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.
WINTER STORM WARNING UNTIL NOON MDT MONDAY FOR WEST GLACIER
REGION.
HIGH WIND WATCH FROM THIS EVENING THROUGH MONDAY MORNING 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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