044
FXUS65 KMSO 260758
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1258 AM MST FRI DEC 26 2025
DISCUSSION
KEY MESSAGES:
- SNOW IMPACTS TRAVEL: TODAY THROUGH SATURDAY, DEFINITELY ON
PASSES BUT VALLEYS BECOME PROBLEMATIC BEGINNING THIS EVENING.
- HIGH WIND/OUTAGE RISK (TODAY): SOUTHWESTERLY GUSTS OF 30-45 MPH
(VALLEYS) AND 60+ MPH (MOUNTAINS) ARRIVE LATE THIS MORNING/AFTERNOON.
SATURATED SOILS WILL MAKE TREES MORE PRONE TO FALLING,
INCREASING THE RISK OF POWER OUTAGES.
- SATURDAY ARCTIC PUSH: FLASH FREEZE POTENTIAL AS BITTERLY COLD
AIR MOVES WEST OF THE DIVIDE SATURDAY MORNING. STRONG NORTHEAST
WINDS WILL DEVELOP IN PRONE CANYONS AND GAP AREAS (E.G., BAD
ROCK CANYON).
- BUILDING RIDGE (EARLY NEXT WEEK): COLD AND MUCH DRIER CONDITIONS
STARTING SUNDAY.
THIS MORNING: TRANSITION PERIOD
RESIDUAL LOW STRATUS AND PATCHY FOG WILL PERSIST EARLY THIS MORNING,
EVENTUALLY LIFTING AS VERTICAL MIXING INCREASES. MEANWHILE, A
DISTURBANCE PIVOTING OFF THE PARENT UPPER-LEVEL LOW ALONG THE NORTHERN
CALIFORNIA COAST WILL BRING WIDESPREAD SHOWERS TO THE REGION BY
MID-TO-LATE MORNING.
-MOUNTAIN PASSES: MINOR TRAVEL IMPACTS ARE EXPECTED THIS
MORNING DUE TO LIGHT, SLUSHY SNOW ACCUMULATIONS.
-LEMHI COUNTY: COLD AIR TRAPPED IN THE VALLEYS MAY SUPPORT A
BRIEF WINDOW OF WINTRY MIX (SNOW AND FREEZING RAIN) BEFORE TRANSITIONING
TO SNOW LATER TODAY.
-WIND: SOUTHWEST WINDS WILL STRENGTHEN BY LATE MORNING. A WIND
ADVISORY IS IN EFFECT FOR SOUTHWEST MONTANA INCLUDING THE
BITTERROOT VALLEY, BUTTE, AND THE BLACKFOOT REGION FOR GUSTS
UP TO 55 MPH, PRIMARILY THIS AFTERNOON.
THIS AFTERNOON THROUGH SATURDAY: POTENT COLD FRONT
A ROBUST PACIFIC FRONT ARRIVES LATE THIS MORNING/AFTERNOON,
INTRODUCING A HIGH- IMPACT COMBINATION OF WIND AND SNOW.
-SNOW AND SQUALLS: WIDESPREAD SNOW AT PASS LEVELS BEGINS BY LATE
THIS MORNING. A TRANSITION TO CONVECTIVE SNOW SHOWERS IS
EXPECTED TONIGHT INTO SATURDAY MORNING, WITH LOCALIZED SNOW
SQUALLS POSSIBLE. WHILE THE MOST INTENSE SQUALLS WILL FAVOR
THE CONTINENTAL DIVIDE, SOUTHWEST MONTANA, AND LEMHI COUNTY,
NEARLY ALL LOCATIONS WILL SEE SNOW BY SATURDAY MORNING.
-ICY THREAT: EXPECT A TRANSITION FROM WET TO SLUSHY/ICY ROAD
SURFACES TONIGHT FOR VALLEY LOCATIONS.
-WIND IMPACTS: VALLEY GUSTS OF 30 TO 45 MPH ARE EXPECTED
(CONVECTIVE GUSTS COULD EXCEED 50 MPH), WHILE MOUNTAIN RIDGES
WILL SEE GUSTS OF 50 TO 65+ MPH. GIVEN SATURATED SOILS AND
RECENT ENVIRONMENTAL STRESS, THERE IS A HIGHER-THAN-NORMAL RISK
FOR DOWNED TREES AND POWER OUTAGES.
SATURDAY: ARCTIC INTRUSION
ARCTIC AIR WILL SPILL SOUTH ALONG THE DIVIDE ON SATURDAY MORNING,
BLEEDING WESTWARD THROUGH TERRAIN GAPS SUCH AS MARIAS PASS INTO
NORTHWEST MONTANA.
-CANYON WINDS: A SHARP SHIFT TO N/NE WINDS WILL OCCUR,
ACCELERATING THROUGH CANYONS. THE NORTHERN FLATHEAD VALLEY AND
BAD ROCK CANYON WILL LIKELY SEE THE STRONGEST GUSTS (40-50
MPH).
-FLASH FREEZE: TEMPERATURES PLUMMETING INTO THE TEENS AND LOW
20S WILL QUICKLY FREEZE ANY LINGERING MOISTURE ON ROADS.
-COLD TEMPERATURES: WHILE THE ARCTIC AIR WILL GRADUALLY MODIFY
AS IT MOVES SOUTH AND WEST, THE REMAINING COLD, DRY AIR MASS
WILL SET THE STAGE FOR A FRIGID SUNDAY MORNING. LOWS WILL DROP
INTO THE SINGLE DIGITS FOR MOST WESTERN MONTANA VALLEYS AND
THE TEENS FOR NORTH-CENTRAL IDAHO LOWER ELEVATIONS.
SUNDAY THROUGH LATE NEXT WEEK
ENSEMBLE CLUSTERS ARE IN GOOD AGREEMENT THAT A HIGH-PRESSURE
RIDGE WILL BUILD OVER THE PACIFIC NORTHWEST, LEADING TO A MUCH
DRIER PERIOD. HOWEVER, NORTHWEST FLOW ALOFT MAY ALLOW MINOR
DISTURBANCES TO CLIP THE REGION, MAINTAINING LOW-END PRECIPITATION
CHANCES, PERIODIC CLOUD COVER, AND MORNING FOG/STRATUS.
LOOKING FURTHER AHEAD, CONFIDENCE IS HIGH (NEAR 80%) THAT ANOTHER DEEP
TROUGH WILL SETTLE OVER THE PACIFIC NORTHWEST NEXT THURSDAY OR FRIDAY,
BRINGING A RETURN TO UNSETTLED CONDITIONS.
AVIATION
LOW STRATUS AND VALLEY FOG LINGERING AT SOME TERMINALS WILL LIFT
THROUGH THE MORNING AS VERTICAL MIXING INCREASES. ATTENTION QUICKLY
SHIFTS TO A POTENT STORM SYSTEM ARRIVING LATE TODAY INTO SATURDAY.
-WIND SHEAR & TURBULENCE: STRENGTHENING SOUTHWESTERLY FLOW
ALOFT WILL CREATE WIDESPREAD LOW-LEVEL WIND SHEAR (LLWS) AND
MECHANICAL TURBULENCE THIS MORNING. WHILE SURFACE GUSTS WILL
INCREASE ELSEWHERE THIS MORNING, VALLEY DECOUPLING WILL LIKELY
ENHANCE SHEAR PROFILES FOR SEVERAL HOURS BEFORE WINDS FULLY
MIX DOWN TO THE SURFACE.
-SNOW & FLIGHT CATEGORIES: WIDESPREAD SHOWERS WILL INCREASE
MID/LATE THIS MORNING AS A COLD FRONT PUSHES THROUGH WITH SNOW
LEVELS FALLING THROUGHOUT THE DAY, REACHING MOST VALLEY FLOORS
BY THIS EVENING. BY LATE THIS EVENING INTO EARLY SATURDAY
MORNING, A BAND OF HEAVY SNOW AND GUSTY WINDS IS ANTICIPATED,
FOLLOWED BY FREQUENT SNOW SHOWERS THROUGH SATURDAY AFTERNOON. EXPECT
A TRANSITION FROM VFR/MVFR IN SHOWERS TO PERIODIC IFR
CONDITIONS AT TERMINALS AS SNOW DEVELOPS LATER TONIGHT.
-ARCTIC INTRUSION: A MODIFIED ARCTIC AIRMASS WILL SPILL OVER
THE CONTINENTAL DIVIDE INTO NORTHWEST MONTANA SATURDAY MORNING.
THIS WILL CAUSE AN ABRUPT SHIFT TO NORTHEAST WINDS AT KGPI
ALONG WITH A ROUND OF SNOW SHOWERS.
-SUMMARY: ANTICIPATE PERIODS OF LOW CEILINGS, WIDESPREAD
MOUNTAIN OBSCURATIONS, REDUCED VISIBILITIES, AND GUSTY WINDS
ACROSS THE REGION THROUGH SATURDAY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY FROM 8 AM FRIDAY TO 2 PM MST SATURDAY
FOR LOWER CLARK FORK REGION.
WINTER WEATHER ADVISORY FROM 5 AM FRIDAY TO 8 PM MST SATURDAY
FOR BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM NOON FRIDAY TO 5 PM MST SATURDAY
FOR KOOTENAI/CABINET REGION.
WINTER WEATHER ADVISORY FROM 8 AM FRIDAY TO 5 PM MST SATURDAY
FOR WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 8 PM FRIDAY TO 8 PM MST SATURDAY
FOR FLATHEAD/MISSION VALLEYS.
WIND ADVISORY FROM 5 AM TO 5 PM MST FRIDAY FOR
MISSOULA/BITTERROOT VALLEYS.
WINTER WEATHER ADVISORY FROM 2 AM TO 5 PM MST SATURDAY FOR
MISSOULA/BITTERROOT VALLEYS.
WIND ADVISORY FROM 6 AM FRIDAY TO 5 AM MST SATURDAY FOR
BUTTE/BLACKFOOT REGION.
WINTER WEATHER ADVISORY FROM 5 AM TO 8 PM MST SATURDAY FOR
BUTTE/BLACKFOOT REGION.
WIND ADVISORY FROM 8 AM FRIDAY TO MIDNIGHT MST FRIDAY NIGHT FOR
POTOMAC/SEELEY LAKE REGION.
WINTER WEATHER ADVISORY FROM 11 AM FRIDAY TO 8 PM MST SATURDAY
FOR POTOMAC/SEELEY LAKE REGION.
ID...WINTER WEATHER ADVISORY FROM 7 AM FRIDAY TO 1 PM PST SATURDAY
FOR NORTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY FROM 4 AM FRIDAY TO 7 PM PST SATURDAY
FOR SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY FROM 4 PM FRIDAY TO 10 AM PST SATURDAY
FOR OROFINO/GRANGEVILLE REGION.
WINTER WEATHER ADVISORY UNTIL 8 PM MST SATURDAY FOR EASTERN
LEMHI COUNTY...WESTERN LEMHI COUNTY.
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