927
FXUS65 KMSO 121929
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1229 PM MST FRI DEC 12 2025
DISCUSSION
KEY MESSAGES:
- LINGERING HAZARDS: MOUNTAIN SNOW AND VALLEY RAIN SHOWERS WILL
PERSIST THROUGH TODAY.
- FOG POTENTIAL: DENSE FOG AND LOW CLOUDS ARE EXPECTED IN VALLEYS
EACH MORNING FROM SATURDAY THROUGH MONDAY.
- A WEAK TO MODERATE ATMOSPHERIC RIVER ARRIVING MONDAY THROUGH
WEDNESDAY.
LIGHT TO MODERATE SNOW WILL CONTINUE TO CREATE SLICK CONDITIONS ON
HIGHWAY 2 FROM WEST GLACIER TO MARIAS PASS IN NORTHWEST MONTANA
THROUGH EARLY TOMORROW. ARCTIC AIR WILL REMAIN TRAPPED AGAINST THE
CONTINENTAL DIVIDE, BLOCKED BY STRONG WESTERLY WINDS ALOFT.
ELSEWHERE ACROSS THE REGION, EXPECT PERSISTENT LIGHT SHOWERS AS
THE REMNANTS OF THIS WEEK'S ATMOSPHERIC RIVER SLOWLY MOVE OUT OF
THE AREA.
HIGH PRESSURE WILL BUILD OVER THE NORTHERN ROCKIES TOMORROW,
BRINGING A BRIEF PERIOD OF DRY CONDITIONS. HOWEVER, DUE TO RECENT
MOISTURE, FOG AND LOW CLOUDS ARE EXPECTED TO DEVELOP EACH MORNING
THROUGH MONDAY. VALLEYS IN WESTERN MONTANA AND NORTH-CENTRAL MAY
SEE DENSE FOG AT TIMES, SO PLAN ACCORDINGLY FOR WEEKEND TRAVEL.
A PROLONGED ATMOSPHERIC RIVER IS EXPECTED TO IMPACT WESTERN
MONTANA AND NORTH-CENTRAL IDAHO AGAIN FROM MONDAY AFTERNOON
THROUGH WEDNESDAY, BRINGING MODERATE TO HEAVY PRECIPITATION. SNOW
LEVELS WILL START AROUND 7,000 FEET ON MONDAY BEFORE FALLING TO
VALLEY FLOORS BEHIND A COLD FRONT EARLY WEDNESDAY.
BEFORE SNOW LEVELS FALL, PRECIPITATION WILL FALL AS RAIN FOR MOST
AREAS. THE FORECAST CALLS FOR 1 TO 2 INCHES OF RAIN IN THE VALLEYS
OF LINCOLN, MINERAL, AND SANDERS COUNTIES IN WESTERN MONTANA, AS
WELL AS CLEARWATER AND IDAHO COUNTIES IN IDAHO. MOUNTAINS IN THESE
REGIONS COULD SEE 2 TO 3 INCHES OF PRECIPITATION. AREAS FURTHER
SOUTH AND EAST IN WESTERN MONTANA WILL LIKELY SEE 1 INCH OR LESS.
A HIGH-END SCENARIO COULD BRING TOTALS 1 TO 2 INCHES HIGHER THAN
THE ESTIMATES GIVEN ABOVE FOR NORTHWEST MONTANA AND NORTH-CENTRAL
IDAHO.
IMPACTS: DUE TO ALREADY SATURATED GROUND, PARTICULARLY IN NORTHWEST
MONTANA, THIS RAINFALL INCREASES THE RISK OF ROCKSLIDES, LANDSLIDES,
SHARP RISES ON STREAMS AND RIVERS, AND MINOR FLOODING. PLEASE
CONTINUE TO MONITOR FORECAST UPDATES AND ACTIVE FLOOD WATCHES AS
THIS SYSTEM APPROACHES.
MOISTURE WILL CONTINUE TO STREAM OVER THE NORTHERN ROCKIES BEHIND
THE COLD FRONT ON WEDNESDAY, TURNING RAIN TO SNOW DOWN TO VALLEY
FLOORS FOR THE REST OF THE WEEK. WHILE 1 TO 2 FEET OF SNOW IS
POSSIBLE IN THE MOUNTAINS, VALLEY ACCUMULATIONS WILL VARY
SIGNIFICANTLY AS MOST SNOW WILL FALL IN NARROW BANDS.
AVIATION
THE REMNANTS OF AN ATMOSPHERIC RIVER WILL CONTINUE TO
BRING LIGHT VALLEY RAIN AND MOUNTAIN SNOW SHOWERS THROUGH THE
EVENING. PERIODIC VISIBILITY REDUCTIONS CAN BE EXPECTED FOR ALL
AVIATION SITES. HIGH PRESSURE WILL BUILD OVER THE NORTHERN ROCKIES
SATURDAY INTO MONDAY, LEADING TO THE DEVELOPMENT OF VALLEY FOG AND
STRATUS EACH MORNING. FOG MAY BECOME DENSE AT TIMES, WITH
VISIBILITY DROPPING TO 1/2SM OR 1/4SM DURING MORNING HOURS AT KGPI
(KALISPELL), KMSO (MISSOULA), AND KHRF (HAMILTON).
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 5 AM MST SATURDAY FOR WEST GLACIER
REGION.
ID...NONE.
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