244
FXUS65 KMSO 040859
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
259 AM MDT SAT OCT 4 2025
DISCUSSION
KEY MESSAGES:
- SNOW FOR THE HIGHER TERRAIN TODAY AND INTO SUNDAY, ESPECIALLY
AROUND GLACIER NATIONAL PARK.
- WIDESPREAD FROST/FREEZE FOR MONDAY AND TUESDAY MORNINGS.
SATELLITE IMAGERY EARLY THIS MORNING INDICATES A BROAD TROUGH OF
LOW PRESSURE NORTH OF THE BORDER, AND A DEEP TROUGH OVER THE GREAT
BASIN. THE NORTHERN TROUGH WILL DIG SOUTH TODAY, PUSHING A
BACKDOOR COLD FRONT OVER THE CONTINENTAL DIVIDE FROM THE EAST THIS
EVENING. THE SOUTHERN TROUGH WILL MOVE TO THE NORTHEAST, SENDING
PACIFIC MOISTURE UP FROM THE SOUTH. PRECIPITATION ASSOCIATED WITH
THESE SYSTEMS WILL CONTINUE TODAY AND INTENSIFY TONIGHT. SNOW
LEVELS WILL COME DOWN TO AROUND 4000 FEET FOR MUCH OF THE
CONTINENTAL DIVIDE, AND AS LOW AS ABOUT 3000 FEET IN AND AROUND
GLACIER NATIONAL PARK. THE EASTERLY, WRAP AROUND NATURE OF THIS
STORM SYSTEM WILL FAVOR THE DIVIDE. THERE IS ABOUT A 60% CHANCE
FOR 6 INCHES OF SNOW ABOVE 7000 FEET, AND THE SAME CHANCES FOR 2
INCHES AT MARIAS PASS IN 24 HOURS ENDING ON SUNDAY AFTERNOON. ANY
SNOW THAT FALLS IN THE LOWER ELEVATIONS WILL LIKELY MELT ON
CONTACT WITH ROAD SURFACES. IN ADDITION TO SNOW, THE COLD FRONT
FROM THE NORTHERN TROUGH WILL BRING INCREASING NORTHEASTERLY WINDS
TO NORTHWEST MONTANA, WITH ABOUT A 60-70% CHANCE OF EXCEEDING 30
MPH ALONG THE DIVIDE, AS WELL AS ALONG THE CRESTS OF THE
WHITEFISH, SWAN, AND FLATHEAD RANGES. DUE TO THESE IMPACTS, A
WINTER STORM WARNING IS IN EFFECT FOR THE GLACIER PARK REGION
ABOVE 5500 FEET FROM MIDNIGHT TONIGHT THROUGH NOON ON SUNDAY.
THOSE WITH PLANS TO RECREATE IN THE BACKCOUNTRY OF THE GLACIER
PARK REGION THIS EVENING THROUGH SUNDAY SHOULD BE PREPARED FOR
WINTER WEATHER.
AS THE FRONT MOVES SOUTH EARLY SUNDAY, SNOW WILL ALSO IMPACT THE
MOUNTAINS OF THE SEELEY LAKE/POTOMAC REGION, AS WELL AS THE
ANACONDA/PINTLER RANGE. WINTER WEATHER ADVISORIES ARE IN EFFECT
FOR THESE AREAS. AGAIN, BE PREPARED FOR WINTER CONDITIONS IF YOU
ARE HEADING INTO THE BACKCOUNTRY THIS WEEKEND.
AS THE DISTURBANCE MOVES OUT OF THE AREA LATE SUNDAY INTO MONDAY,
A DRIER AIRMASS WILL SETTLE IN OVER THE REGION. WITH THE
COMBINATION OF CLEAR SKIES AND THIS COLDER AIRMASS, THE FIRST
WIDESPREAD HARD FREEZE WILL IMPACT THE MAJORITY OF THE VALLEYS IN
WESTERN MONTANA. OVERNIGHT LOWS IN THE 20S WILL BE COMMONPLACE,
WHILE THE COLDER VALLEY LOCALES SUCH AS PHILIPSBURG AND THE UPPER
CLARK FORK AND BLACKFOOT RIVER VALLEYS WILL EXPERIENCE LOWS IN THE
TEENS. THE LOWER VALLEYS OF IDAHO AND CLEARWATER COUNTIES WILL
REMAIN ABOVE FREEZING BUT WILL STILL LIKELY SEE THEIR FIRST FROST
IN AREAS FROM OROFINO TO GRANGEVILLE.
A RIDGE OF HIGH PRESSURE BUILDS OVER THE REGION BY THE MIDDLE OF
NEXT WEEK, ALLOWING FOR A GRADUAL WARMING TREND WITH CHILLY
MORNING LOWS AND SEASONABLE AFTERNOON HIGHS.
AVIATION
MORNING FOG AND/OR LOW STRATUS WILL BE A POSSIBILITY
AT KMSO AND KHRF DURING PERIODS OF CLEARING SKIES. DECREASED
VISIBILITY AND LOWERED CEILINGS WILL BE CAPABLE OF BRINGING FLIGHT
RULES DOWN TO IFR AND BELOW. INCREASED CLOUD COVER BY ABOUT
04/1200Z SHOULD RESULT IN IMPROVED VISIBILITY, THOUGH LOW CEILINGS
COULD PERSIST INTO THE MID MORNING HOURS. EXPECT WIDESPREAD CLOUD
COVER TO OBSCURE TERRAIN ACROSS THE NORTHERN ROCKIES TODAY. RAIN
SHOWERS WILL BECOME WIDESPREAD THIS AFTERNOON. FURTHER CHANGES
ARRIVE EARLY SUNDAY AS A BACKDOOR COLD FRONT INCREASES NORTHEAST
WINDS (ESPECIALLY NEAR THE DIVIDE) AND SHOWER COVERAGE WITH SNOW
LEVELS DROPPING TO 4000-5000 FEET.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO NOON MDT SUNDAY
FOR WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON MDT SUNDAY
FOR BUTTE/BLACKFOOT REGION...POTOMAC/SEELEY LAKE REGION.
ID...NONE.
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