675
FXUS65 KMSO 112030
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
130 PM MST THU DEC 11 2025
DISCUSSION
KEY MESSAGES:
- FLOODING THREAT CONTINUES IN FAR NORTHWEST MONTANA.
- PRECIPITATION CONTINUES INTO FRIDAY BUT IN DIMINISHED QUANTITIES
COMPARED TO WEDNESDAY/EARLY TODAY.
- SNOW RETURNS TO THE GLACIER REGION ON EARLY FRIDAY.
HYDROLOGY AND PRECIPITATION: THE ATMOSPHERIC RIVER PLUME HAS
SHIFTED SOUTH OUT OF NORTHWEST MONTANA INTO NORTH-CENTRAL IDAHO
AND WEST-CENTRAL MONTANA. WHILE CONSIDERABLE FLOODING CONTINUES IN
PARTS OF LINCOLN AND SANDERS COUNTIES DUE TO EARLIER RAIN AND
SNOWMELT, THE BREAK IN PRECIPITATION ACROSS THE NORTHERN HALF OF
NORTHWEST MONTANA WILL PERSIST THROUGH THIS EVENING. THE MOISTURE
PLUME IS EXPECTED TO SHIFT BACK NORTHWARD LATE TONIGHT, STALLING
OVER NORTHWEST MONTANA ON FRIDAY. PRECIPITATION AMOUNTS ON FRIDAY
WILL BE LIGHTER THAN THE WEDNESDAY EVENT, WITH VALLEYS LIKELY
SEEING ANOTHER 0.15-0.30 INCHES AND MOUNTAINS RECEIVING 0.50-1.00
INCHES. SNOW LEVELS WILL DROP TO 4000-5000 FEET TONIGHT IN THE
IMPACTED AREAS BEFORE REBOUNDING TO 6000 FEET ON FRIDAY. FLOODING
REMAINS A CONCERN IN PREVIOUSLY AFFECTED AREAS, THOUGH SIGNIFICANT
EXPANSION INTO NEW AREAS IS NOT ANTICIPATED.
WINTER WEATHER: A WINTRY COMPONENT WILL DEVELOP BY THIS EVENING
AS ARCTIC AIR BANKS AGAINST THE CONTINENTAL DIVIDE. THIS COLD AIR
WILL FILTER DOWN THE US-2 CORRIDOR, THOUGH UNCERTAINTY REMAINS
REGARDING HOW FAR WEST IT WILL PROGRESS. SNOW IS EXPECTED AT
MARIAS PASS, OCCASIONALLY REACHING DOWN TO ESSEX. A SECONDARY
CONCERN IS THE POTENTIAL FOR LIGHT FREEZING RAIN IF THE SHALLOW
COLD AIR REACHES WEST GLACIER. GIVEN THE POTENTIAL FOR HAZARDOUS
TRAVEL, A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR THE GLACIER
REGION FROM FRIDAY INTO EARLY SATURDAY.
EXTENDED FORECAST: UPPER-LEVEL RIDGING BUILDS OVER THE WEEKEND,
MAINTAINING MILD TEMPERATURES BUT INCREASING THE THREAT OF FOG AND
LOW STRATUS DEVELOPMENT. ANOTHER ATMOSPHERIC RIVER ARRIVES LATE
MONDAY INTO TUESDAY WITH SNOW LEVELS INITIALLY NEAR 7000 FEET.
MOST MODELS INDICATE A STRONG PACIFIC COLD FRONT PASSING LATE
TUESDAY OR WEDNESDAY, WHICH WILL LIKELY PRODUCE STRONG WINDS AND
CRASH SNOW LEVELS TO VALLEY FLOORS. THIS SIGNALS A REGIME CHANGE,
WITH WIDESPREAD WINTER WEATHER IMPACTS INCLUDING VALLEY SNOW
BECOMING MORE LIKELY BY THE MIDDLE OF NEXT WEEK. STAY TUNED FOR
THIS EXPECTED RETURN TO WINTER!
AVIATION
THE ATMOSPHERIC RIVER HAS SAGGED SOUTHWARD INTO NORTH-CENTRAL
IDAHO AND INTO WEST-CENTRAL MONTANA WITH LOWERED CEILINGS AND REDUCED
VISIBILITY THIS AFTERNOON. THE STREAM OF MOISTURE WILL WORK NORTHWARD AGAIN
TONIGHT/FRIDAY IMPACTING NORTHWEST MONTANA. GUSTY WINDS AND SIGNIFICANT
WIND SHEAR WILL CONTINUE TO DIMINISH THIS AFTERNOON/EVENING. THERE IS AN
OUTSIDE CHANCE (10-15%) OF LIGHT FREEZING RAIN AT KGPI EARLY FRIDAY AS A
SHALLOW INTRUSION OF ARCTIC AIR WORKS DOWN US-2.
MSO WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH UNTIL 5 PM MST THIS AFTERNOON FOR FLATHEAD/MISSION
VALLEYS...KOOTENAI/CABINET REGION...LOWER CLARK FORK
REGION...POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM MST
SATURDAY FOR WEST GLACIER REGION.
WIND ADVISORY UNTIL 7 PM MST THIS EVENING FOR BUTTE/BLACKFOOT
REGION.
ID...FLOOD WATCH UNTIL 4 PM PST THIS AFTERNOON FOR NORTHERN
CLEARWATER MOUNTAINS...OROFINO/GRANGEVILLE REGION.
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