732
FXUS65 KMSO 041942
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
142 PM MDT SAT OCT 4 2025
DISCUSSION
KEY MESSAGES:
- SNOW FOR THE HIGHER TERRAIN TONIGHT AND SUNDAY, ESPECIALLY
AROUND GLACIER NATIONAL PARK.
- WIDESPREAD FROST/FREEZE FOR MONDAY AND TUESDAY MORNINGS.
SATELLITE IMAGERY THIS AFTERNOON SHOWS A BROAD TROUGH OF LOW
PRESSURE DIGGING SOUTH THROUGH BRITISH COLUMBIA AND ALBERTA. THIS
STORM SYSTEM IS STILL ON TRACK TO BRING OUR FIRST WIDESPREAD
MOUNTAIN SNOWFALL TO AREAS ALONG THE CONTINENTAL DIVIDE,
ESPECIALLY GLACIER NATIONAL PARK, FROM TONIGHT THROUGH SUNDAY
AFTERNOON. THE LATEST GUIDANCE CONTINUES TO SUGGEST 4 TO 8 INCHES
OF SNOWFALL FOR ELEVATIONS ABOVE 5500 FEET IN THE GNP REGION, WITH
A 40 PERCENT PROBABILITY FOR ACCUMULATIONS REACHING 10 INCHES AT
ELEVATIONS SIMILAR TO LOGAN PASS. A WINTER STORM WARNING REMAINS
IN EFFECT FROM MIDNIGHT TONIGHT TO NOON ON SUNDAY. SNOW LEVELS ON
SUNDAY MORNING COULD BE AS LOW AS 3000 FEET ALONG HIGHWAY 2 FROM
WEST GLACIER TO MARIAS PASS, WITH AROUND A 60 PERCENT PROBABILITY
FOR UP TO 2 INCHES OF SLUSHY SNOW ON THE PASS ITSELF. ANY SNOW
THAT FALLS IN THE LOWER VALLEYS WILL BE LESS THAN AN INCH AND WILL
LIKELY MELT UPON CONTACT WITH ROAD SURFACES. THOSE WITH PLANS TO
RECREATE IN THE BACKCOUNTRY OF THE GLACIER PARK REGION SHOULD
CONSIDER POSTPONING THEM.
AS THE FRONT MOVES SOUTH EARLY SUNDAY, SNOW IS ALSO EXPECTED TO
IMPACT THE MOUNTAINS OF THE SEELEY LAKE/POTOMAC REGION, AS WELL AS
THE ANACONDA/PINTLER, BITTERROOT, AND SAPPHIRE RANGES; WINTER
WEATHER ADVISORIES REMAIN IN EFFECT FOR THESE LOCATIONS. PLEASE
PACK ADDITIONAL SUPPLIES FOR COLD, WET, AND BREEZY CONDITIONS IF
YOU ARE HEADING INTO THE BACKCOUNTRY.
GUSTY EAST-NORTHEAST WINDS WILL ALSO ACCOMPANY THE COLD FRONT AS
IT MOVES SOUTH ACROSS WESTERN MONTANA. THE STRONGEST WIND GUSTS
ARE EXPECTED OVERNIGHT TONIGHT, FROM MIDNIGHT TO 6 AM SUNDAY. THE
HIGHEST WIND IMPACTS ARE LIKELY TO BE OVER FLATHEAD LAKE AND ALONG
HIGHWAY 35 ON THE EAST SIDE OF THE LAKE. GUSTS AROUND 30 MPH, WITH
ISOLATED STRONGER GUSTS NEARING 40 MPH, ARE POSSIBLE NEAR YELLOW
BAY. CHOPPY CONDITIONS ARE LIKELY ON THE LAKE EARLY SUNDAY
MORNING, WITH WINDS DIMINISHING IN STRENGTH LATE SUNDAY MORNING OR
EARLY AFTERNOON.
AS THE DISTURBANCE MOVES OUT OF THE AREA LATE SUNDAY INTO MONDAY,
A DRIER AND COLDER AIRMASS WILL SETTLE IN OVER THE REGION. WITH
THE COMBINATION OF CLEAR SKIES AND THIS COLD AIRMASS, THE FIRST
WIDESPREAD HARD FREEZE IS EXPECTED FOR THE MAJORITY OF THE VALLEYS
OF WESTERN MONTANA SUNDAY NIGHT INTO MONDAY MORNING. THE LOWER
VALLEYS OF IDAHO'S CLEARWATER COUNTY ARE EXPECTED TO 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
SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP THIS
AFTERNOON. EARLIER CLEARING ACROSS NORTHWEST MONTANA ALLOWED FOR
DAYTIME HEATING TO INCREASE INSTABILITY, LEADING TO REPORTS OF
SMALL HAIL AND THE POTENTIAL FOR ISOLATED LIGHTNING. ACROSS THE
ENTIRE REGION, STRONGER SHOWERS WILL BRIEFLY LOWER CEILINGS AND
VISIBILITY TO MVFR. A MORE SIGNIFICANT DETERIORATION IN
CONDITIONS IS EXPECTED TONIGHT AS A COLD FRONT ARRIVES FROM THE
NORTH. THIS WILL PRODUCE WIDESPREAD MVFR CEILINGS, EXTENSIVE
MOUNTAIN OBSCURATION, AND A SHIFT TO NORTHERLY AND EASTERLY WINDS.
SNOW LEVELS WILL FALL WITH ACCUMULATIONS EXPECTED ABOVE
APPROXIMATELY 5,500 FEET OVERNIGHT. CONSEQUENTLY, A RAIN/SNOW
MIX IS POSSIBLE IN SOME VALLEYS, INCLUDING AT THE KGPI AND KBTM
TERMINALS. THESE SHOWERY CONDITIONS WILL LINGER THROUGH SUNDAY
MORNING.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO NOON MDT SUNDAY
FOR WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 3 AM TO NOON MDT SUNDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON MDT SUNDAY
FOR BUTTE/BLACKFOOT REGION...POTOMAC/SEELEY LAKE REGION.
ID...NONE.
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