979
FXUS65 KMSO 091921
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
121 PM MDT THU OCT 9 2025
DISCUSSION
KEY MESSAGES:
- A WARM, WET SYSTEM COMING IN FOR SATURDAY WILL TRANSITION TO A
COLD SNOWY ONE SATURDAY NIGHT.
- GLACIER NATIONAL PARK WILL BE HARDEST HIT WITH SNOW, BUT EXPECT
SEVERAL INCHES OF MOUNTAIN SNOW ACROSS THE WHOLE REGION.
- THE COLD, SNOWY WEATHER WILL LAST THROUGH THE EARLY WEEK.
A VERY LARGE AND COLD CLOSED LOW OFF THE WEST COAST WILL GET
REABSORBED INTO THE STORM TRACK THIS WEEKEND AND EARLY NEXT WEEK.
AS THAT HAPPENS, SOUTHERLY FLOW WILL BECOME MORE ESTABLISHED OVER
THE REGION PULLING AIR FROM A VERY WARM, MOIST AIR MASS INTO THE
NORTHERN ROCKIES. SNOW LEVELS WILL SHOOT UP OVER 10,000 FT
ELEVATION IN SOME AREAS OVER 12,000 FT AS A RESULT OF THE WARM
SOUTHERLY FLOW ON FRIDAY. AS THE RAIN ARRIVES ON SATURDAY, THE
SNOW LEVELS WILL GRADUALLY FALL, UNTIL A COLD FRONT SATURDAY
EVENING CAUSES THEM TO COME CRASHING DOWN.
SNOW LEVELS WILL DROP DOWN BELOW 5,000 FT BY SUNDAY MORNING IN
NORTHWEST MONTANA. THEY'LL KEEP FALLING AND ARE EXPECTED TO BOTTOM
OUT BELOW 3,000 FT ACROSS MUCH OF NORTHWEST MONTANA BY MONDAY
MORNING. FURTHER WEST IN CENTRAL IDAHO, THEY'RE EXPECTED TO GET
BELOW 5,000 FT. OFTEN IN THESE SCENARIOS THERE IS MUCH LESS
MOISTURE IN THE COLD AIR MASS BEHIND THE FRONT, BUT THAT IS NOT
THE CASE THIS TIME. TYPHOONS IN THE WESTERN PACIFIC OCEAN HAVE
INJECTED QUITE A LOT OF MOISTURE INTO THE STORM AS THEY HEADED
NORTH, AND SOME OF THAT MOISTURE WILL BE EMBEDDED BEHIND THE COLD
FRONT. SO THE RAIN WILL TRANSITION TO SNOW, AND IT WILL KEEP
COMING.
ENSEMBLE FORECASTS CONTINUE TO SHOW A LOT OF VARIATION IN THE
DETAILS, BUT THE BIG PICTURE AND MAIN IMPACTS ARE PRETTY CLEAR.
THE MOUNTAINS, ESPECIALLY GLACIER NATIONAL PARK WILL START
ACCUMULATING SNOW ON SATURDAY, AND THE SNOW INTENSITY WILL
INCREASE THROUGH SUNDAY. BY MONDAY MORNING, THERE IS A 20% TO 55%
CHANCE FOR 1 INCH OR MORE OF NEW SNOW ACCUMULATION IN PLACES LIKE
KALISPELL, WHITEFISH, EUREKA, AND THE SWAN VALLEY IN NORTHWEST
MONTANA. PASSES LIKE MARIAS PASS AND LOGAN PASS HAVE A 50 TO 80%
CHANCE OF PICKING UP 8 INCHES OR MORE OF SNOW BY MONDAY MORNING.
HIGHER ELEVATIONS AND MORE REMOTE AREAS INCLUDING THE SWAN,
WHITEFISH, AND MISSION MOUNTAINS WILL GET EVEN MORE SNOW.
GENERALLY SPEAKING, THE MOUNTAINS OF WESTERN MONTANA AND INTO
CENTRAL IDAHO INCLUDING THE ANACONDA-PINTLER, BITTERROOT,
SAPPHIRE, AND CABINET MOUNTAINS WILL PICK UP SEVERAL INCHES OF
SNOW. THOSE TRAVELLING THROUGH THE BACK COUNTRY FOR RECREATION
SHOULD BE PREPARED FOR SNOW THIS WEEKEND AND EARLY NEXT WEEK.
IN THE LONGER TERM, TEMPERATURES WILL RECOVER TO NEAR AVERAGE
HIGHS BY LATE NEXT WEEK, BUT THE PATTERN IS EXPECTED TO REMAIN
ACTIVE WITH CONTINUED CHANCES FOR SHOWERS, ESPECIALLY IN THE
MOUNTAINS.
AVIATION
SOUTHERLY FLOW TODAY IS CAUSING INCREASED CLOUD COVER
AHEAD OF THE NEXT WEATHER SYSTEM WITH MINIMAL IMPACTS TO AVIATION.
FRIDAY EVENING EXPECT RAIN TO START ACROSS THE REGION WITH MAINLY
MVFR IMPACTS AT AREA TERMINALS. SATURDAY IT WILL START SNOWING IN
THE MOUNTAINS, AND SNOW WILL BE POSSIBLE AT AREA TERMINALS SUNDAY
NIGHT, ESPECIALLY KGPI AND KBTM.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH MONDAY MORNING
FOR BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT
REGION...KOOTENAI/CABINET REGION...LOWER CLARK FORK
REGION...POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
ID...WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY
MORNING FOR NORTHERN CLEARWATER MOUNTAINS...SOUTHERN
CLEARWATER MOUNTAINS.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH LATE SUNDAY
NIGHT FOR EASTERN LEMHI COUNTY...WESTERN LEMHI COUNTY.
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