634
FXUS65 KMSO 191943
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1243 PM MST FRI DEC 19 2025
DISCUSSION
KEY MESSAGES:
- CURRENT: HEAVY MTN SNOW, STRONG WINDS, & DIFFICULT TRAVEL
ACROSS LOLO AND LOST TRAIL PASSES. SNOW LEVELS FALLING TO
VALLEY FLOORS OF SW MONTANA, LEMHI COUNTY.
- AS SKIES CLEAR AND TEMPERATURES DROP TONIGHT, WET ROADS WILL
BEGIN TO REFREEZE PROMOTING AREAS OF BLACK ICE INTO SATURDAY
MORNING.
- WEEKEND: COLDER SATURDAY WITH SCATTERED SNOW SHOWERS AND LIGHT
VALLEY ACCUMULATION POSSIBLE. LULL SUNDAY MORNING BEFORE NEXT
MOISTURE SURGE ARRIVES SUNDAY NIGHT.
- REMAIN AWARE OF TRAVEL CONDITIONS DURING CRITICAL HOLIDAY AND
FOOTBALL TRAVEL WINDOW.
DEEP-LAYER MOISTURE CONTINUES TO STREAM INTO THE NORTHERN ROCKIES
THIS AFTERNOON RELATED TO YET ANOTHER SURGE FROM AN ATMOSPHERIC
RIVER PENETRATING FAR INLAND. FRONTAL AND OROGRAPHIC LIFTING AHEAD
OF A SOUTHWARD PROGRESSING COLD FRONT CONTINUES TO PRODUCE HEAVY
PRECIPITATION RATES WITH SNOW LEVELS RETURNING TO MANY VALLEY
LOCATIONS IN SOUTHWEST MONTANA, NORTH-CENTRAL IDAHO AND LEMHI
COUNTY THROUGH THE REST OF THE DAY TODAY.
ALONG AND BEHIND THE FRONT, 35-50 MPH GUSTS HAVE MOSTLY BEGUN TO
SUBSIDE. FOR THAT REASON, WIND ADVISORIES HAVE BEEN ALLOWED TO
EXPIRE ON SCHEDULE; HOWEVER, BREEZY CONDITIONS WILL LIKELY
CONTINUE THROUGH MUCH OF THE WEEKEND AS COLDER AIR CONTINUES TO
FILTER IN.
PRECIPITATION HAS TAPERED OFF SIGNIFICANTLY BEHIND THE FRONT AS
WELL, WITH EVEN SOME POCKETS OF BLUE SKY BEGINNING TO APPEAR AS
THAT DRIER AIR WORKS ITS WAY INTO THE REGION. WITH THIS PRONOUNCED
DRYING, THE WINTER WEATHER ADVISORY FOR THE LOWER CLARK FORK
REGION AND LOOKOUT PASS HAS ENDED EARLY DUE TO THE REDUCED
LIKELIHOOD OF WIDESPREAD IMPACTS THROUGH THE REST OF THE DAY.
MOUNTAIN LOCATIONS ALONG AND SOUTH OF US-12/I-90 WILL CONTINUE TO
SEE MODERATE TO HEAVY SNOWFALL RATES AS THE BULK OF THE MOISTURE
DRIVES SOUTHWARD THROUGH THE DINNER HOUR THIS EVENING. IN THIS
AREA, PERIODS OF STRONG WINDS (UP TO 45 MPH) AND BLOWING SNOW ARE
ALSO POSSIBLE DURING THIS TIME REDUCING VISIBILITY AND HELPING
COOL ROAD SURFACES, PROMOTING SLICK TRAVEL AND POTENTIAL FOR SNOW
ACCUMULATION EVEN AT LOWER ELEVATIONS.
OVERNIGHT TONIGHT, AS THAT MUCH COOLER AIR MOVES INTO THE REGION,
ANTICIPATE AREAS OF BLACK ICE/REFREEZING WHERE WET ROADS REMAIN
FROM THIS MORNINGS RAINFALL AND OR MELTED SNOW ESPECIALLY ON
BRIDGES, OVERPASSES, AND ELEVATED SURFACES. MID-LEVEL MOISTURE AND
INSTABILITY WILL ALSO BEGIN TO GRADUALLY INCREASE OUT OF THE WEST
AT THIS TIME LEADING TO THE INTRODUCTION OF SCATTERED SNOW
SHOWERS IN NORTHWESTERN AND WEST-CENTRAL MONTANA AS WELL AS
NORTHERN PORTIONS OF CENTRAL IDAHO. ALTHOUGH MOST SHOWERS WILL NOT
BE OVERLY PRODUCTIVE OR INTENSE (EXCEPT IN THE HIGHER TERRAIN AND
UPSLOPE REGIONS) THE COOLER, BREEZY CONDITIONS WILL ALLOW FOR
LIGHT ACCUMULATIONS EVEN ON VALLEY ROADWAYS THROUGH MUCH OF THE
DAY ON SATURDAY. MOUNTAIN AREAS WILL CONTINUE TO SEE STEADY
SNOWFALL RESULTING IN PERIODIC PLOWABLE SNOWFALL OVER PASSES AND
AT HIGHER ELEVATIONS. PLEASE REMAIN ALERT FOR CHANGING DRIVING
CONDITIONS WITH TIME AND WITH LOCATION AS YOU NAVIGATE THIS
IMPORTANT HOLIDAY (AND FOOTBALL!) TRAVEL PERIOD.
A BRIEF LULL IN ADVERSE WEATHER WILL TAKE HOLD BY EARLY SUNDAY
MORNING, BUT NOT FOR LONG, AS ANOTHER PUSH OF MOISTURE ARRIVES OUT
OF THE WEST AND SOUTHWEST LATE SUNDAY INTO MONDAY. SNOW LEVELS
WILL, AGAIN, BEGIN TO RISE, BUT ONLY TOWARD 3,000-3,500 FEET
ACROSS MUCH OF THE AREA WITH MANY VALLEY LOCATIONS IN WESTERN
MONTANA BEGINNING TO FLIRT WITH A RAIN/SNOW MIX. MOISTURE AND
PRECIPITATION AMOUNTS WITHIN THIS TIMEFRAME DO NOT APPEAR TO BE
OVERWHELMINGLY ALARMING, BUT A WIDESPREAD 0.2-0.5 INCHES OF
PRECIPITATION (OR SNOW WATER EQUIVALENT) SEEMS LIKELY WITH
MOUNTAINOUS AREAS POTENTIALLY SEEING DOUBLE THAT AMOUNT.
SHOWERS CONTINUE IN THIS RELATIVELY UNCHANGING PATTERN THROUGH
MUCH OF NEXT WEEK. ANY OVERNIGHT PERIODS OF CLEAR SKIES, CALM
WINDS, AND RESULTING SUFFICIENT COOLING TO NEAR AND BELOW FREEZING
MAY PRODUCE AREAS OF REFREEZING WET SURFACES AND/OR BRING A
CHANGE OF FOLLOWING PRECIPITATION BACK TOWARD ALL SNOW OR MAYBE
EVEN POCKETS OF FREEZING RAIN IF VALLEY COLD POOLS CAN UNDERCUT
THE SLIGHTLY WARMER AIR ALOFT.
AVIATION
THE ATMOSPHERIC RIVER CONTINUES TO SAG SOUTH WITH
WIDESPREAD PRECIPITATION MAINLY ALONG AND SOUTH OF US-12 AS OF
EARLY AFTERNOON. FLOW IS SHIFTING FROM SOUTHWEST TO WEST-
NORTHWEST BEHIND A COLD FRONT STRETCHING FROM SOUTHERN IDAHO
COUNTY INTO SOUTHWEST MONTANA. THE THREAT FOR CONVECTIVE SNOW
SHOWERS WILL INCREASE BEHIND THE FRONT LATE AFTERNOON INTO THE
EVENING HOURS.
CEILINGS/VISIBILITY: AREAS OF MVFR/IFR CONDITIONS PERSIST UNDER
THE MAIN PRECIPITATION SHIELD, ALONG WITH MOUNTAIN OBSCURATIONS.
SNOW LEVELS WILL BE DROPPING TO VALLEY FLOORS BEHIND THE COLD
FRONT. SCATTERED SHOWERS WILL IMPACT THE MOUNTAINS AND VALLEYS
ALIKE TONIGHT INTO SATURDAY BRINGING BRIEF VISIBILITY AND CEILING
REDUCTIONS TO VALLEYS.
WIND: WESTERLY GUSTS OF 20-30 KTS WILL OCCUR UNTIL SUNSET POST FRONTAL
THEN DIMINISH FOR VALLEY LOCATIONS. SOUTHWEST WIND GUSTS OF 15-25
KTS RETURN LATE SATURDAY MORNING.
LLWS/TURBULENCE: MECHANICAL TURBULENCE AND LOW-LEVEL WIND SHEAR
WILL CONTINUE THROUGH THE AFTERNOON. STRONG FLOW ALOFT (70+ KT AT
700MB) OVER MOUNTAIN CRESTS WILL CREATE TURBULENCE AND MOUNTAIN
WAVE ACTIVITY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 11 AM MST SATURDAY FOR WEST
GLACIER REGION.
WINTER STORM WARNING UNTIL 5 PM MST THIS AFTERNOON FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY FOR SOUTHERN
CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
EASTERN LEMHI COUNTY...WESTERN LEMHI COUNTY.
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