541
FXUS65 KMSO 131139
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
539 AM MDT FRI MAR 13 2026
UPDATE
SNOW CONTINUES TO FALL IN THE MISSOULA AND BITTERROOT
VALLEYS. HAVE ISSUED A WINTER WEATHER ADVISORY VALID THROUGH 10
AM THIS MORNING. THE SNOW MAY MIX WITH RAIN OR CHANGE TO RAIN BY
THE AFTERNOON.
PREV DISCUSSION
/ISSUED 413 AM MDT FRI MAR 13 2026/
DISCUSSION...
KEY MESSAGES:
- WINTRY TRAVEL THIS MORNING FROM NORTH-CENTRAL IDAHO INTO WESTERN
MONTANA, THEN AGAIN TONIGHT THROUGH SATURDAY MORNING.
- VALLEYS IN NORTH CENTRAL IDAHO (GRANGEVILLE TO ELK CITY) WILL
REMAIN IN MODERATE RAIN, ELEVATING THE RISK FOR ROCKFALLS, SNOW
SLOUGHING, AND MINOR RIVER RISES.
- AN ARCTIC BOUNDARY MOVING INTO WESTERN MONTANA(80% CHANCE)
SATURDAY EVENING WILL TAP INTO INSTABILITY TO TRIGGER INTENSE
BANDS OF SNOW BETWEEN KALISPELL TO MISSOULA/ALONG I-90/HWY200.
WITH WET ROADS FROM DAYTIME MELTING, A RAPID FREEZE-UP AND SLICK
ROADS ARE POSSIBLE.
AS EXPECTED, THE PARKED ATMOSPHERIC RIVER OVER THE REGION,
COMBINED WITH COOLER TEMPERATURES, HAS ALLOWED SNOW LEVELS TO
FALL TO AROUND 2500 FEET FROM CLEARWATER COUNTY EASTWARDS INTO
WEST-CENTRAL MONTANA. AT MIDNIGHT, GLACIER PARK INTERNATIONAL
AIRPORT IN KALISPELL REPORTED 3.6 INCHES OF SNOW AND HAS LIKELY
RECEIVED MORE SINCE THEN. MISSOULA HAS BEEN GETTING SNOW AND
THERE IS CLOSE TO AN INCH THAT HAS FALLEN ON THE GRASS. ROADS ARE
SNOW- COVERED ALONG THE HIGHWAY 200 CORRIDOR FROM ROGERS PASS TO
TROUT CREEK, AND ALSO IN THE GLACIER REGION. BUT IT APPEARS THAT
IT IS RAINING IN HAMILTON, AWAY FROM THE MAIN PLUME OF MOISTURE.
THIS PLUME OF MOISTURE WILL BE PARKED GENERALLY ALONG
INTERSTATE-90 FROM WASHINGTON STATE INTO MONTANA, GENERALLY 100
MILES NORTH AND SOUTH THROUGH LATE THIS EVENING. SOME LOCATIONS,
LIKE MISSOULA MAY CHANGE BACK TO RAIN THIS AFTERNOON, BUT POINTS
NORTH AND WEST MAY STAY WET SNOW. BY TONIGHT, THE RAIN MAY CHANGE
BACK TO SNOW IN THIS REGION. MORE SNOWFALL IS EXPECTED ACROSS
NORTHWEST MONTANA, SO EXPECT MORE WINTRY TRAVEL. A COLD FRONT
MOVING THROUGH WILL CUT OFF THE WIDESPREAD SNOWFALL ACROSS
LINCOLN, FLATHEAD AND WESTERN SANDERS COUNTY BY DAYBREAK SATURDAY.
IT WILL BE MORE SHOWERY IN THOSE REGIONS DURING THE MORNING.
MEANWHILE THE MOISTURE FROM THE ATMOSPHERIC RIVER WILL HANG ON
JUST A LITTLE WHILE LONGER FROM NORTH-CENTRAL IDAHO, TOWARDS
SOUTHWEST MONTANA SATURDAY MORNING. THE HIGHEST PROBABILITIES FOR
MODERATE PRECIPITATION RATES (0.10" TO 0.30") EXIST FROM
CLEARWATER COUNTY EAST AND SOUTH ACROSS THE CLEARWATER MOUNTAINS
TO THE BITTERROOT MOUNTAINS DURING THIS PERIOD. SO CONTINUE TO
EXPECT HEAVY SNOW IN THE MOUNTAINS, AND INCREASED ROCKFALL IN
IDAHO.
AS THE ATMOSPHERE BECOMES HIGHLY UNSTABLE BY SATURDAY AFTERNOON,
SNOW AND GRAUPEL SHOWERS WILL DEVELOP. OF SIGNIFICANT CONCERN IS
AN ARCTIC BOUNDARY PROJECTED TO PLUNGE SOUTH FROM ALBERTA SATURDAY
EVENING (80% PROBABILITY). THIS FRONT WILL LIKELY TRIGGER INTENSE
SNOW BANDS BETWEEN KALISPELL AND MISSOULA AND EASTWARD TOWARD THE
CONTINENTAL DIVIDE. RAPIDLY FALLING TEMPERATURES ON WET ROADS MAY
CREATE A HIGH RISK FOR FLASH FREEZE CONDITIONS AND DANGEROUS
TRAVEL BEFORE ACTIVITY WANES BY MIDNIGHT.
SUNDAY PROVIDES A BRIEF, COLD REPRIEVE BEFORE OVERRUNNING MOISTURE
FROM A BRITISH COLUMBIA-BOUND ATMOSPHERIC RIVER REACHES THE
REGION SUNDAY NIGHT. THIS WARM-FRONTAL PASSAGE WILL LIKELY
REINTRODUCE WINTRY TRAVEL IMPACTS TO THE MOUNTAINS AND NORTHERN
VALLEYS. LOOKING AHEAD TO NEXT WEEK, ENSEMBLE GUIDANCE STRONGLY
FAVORS THE BUILDING OF A HIGH-AMPLITUDE RIDGE. DESPITE OCCASIONAL
"DIRTY" RIDGE CLOUD COVER, A SIGNIFICANT WARMING TREND IS
EXPECTED, WITH TEMPERATURES REBOUNDING INTO THE 50S AND 60S.
AVIATION...LOW CLOUDS AND CEILINGS ARE EXPECTED TODAY ACROSS THE
REGION AS A PLUME OF MOISTURE IS PARKED GENERALLY 100 MILES NORTH
AND SOUTH OF INTERSTATE 90. KGPI WILL MOST LIKELY REMAIN ALL SNOW
FOR ANY PERIODS OF PRECIPITATION, CAUSING IFR CONDITION AT TIMES.
KMSO MAY TRANSITION BACK TO RAIN BY THE AFTERNOON, ONLY TO RETURN
BACK TO SNOW FRIDAY NIGHT. KBTM WILL EXPERIENCE PERIODS OF SNOW
THROUGH SATURDAY MORNING. KSMN IS GENERALLY FAR AWAY FROM THE MAIN
PLUME, SO IT MAY BE ABLE TO PRODUCE GUSTY WINDS TODAY. ON SATURDAY
SNOW SHOWERS AND BREEZY WINDS ARE EXPECTED. SNOW BANDS ARE
POSSIBLE ACROSS WEST-CENTRAL MONTANA AND COULD PRODUCE MODERATE TO
HEAVY SNOW RATES, GUSTY WINDS AND LOW CEILINGS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING UNTIL NOON MDT SATURDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT REGION...
LOWER CLARK FORK REGION...POTOMAC/SEELEY LAKE REGION...WEST
GLACIER REGION.
WINTER WEATHER ADVISORY UNTIL NOON MDT TODAY FOR
FLATHEAD/MISSION VALLEYS.
WINTER WEATHER ADVISORY UNTIL 10 AM MDT THIS MORNING FOR
MISSOULA/BITTERROOT VALLEYS.
ID...WINTER STORM WARNING UNTIL 11 AM PDT SATURDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR LOWER HELLS
CANYON/SALMON RIVER REGION...NORTHERN CLEARWATER
MOUNTAINS...OROFINO/GRANGEVILLE REGION...SOUTHERN
CLEARWATER MOUNTAINS.
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