204
FXUS65 KMSO 120948
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
348 AM MDT THU MAR 12 2026
DISCUSSION
KEY MESSAGES:
- PEAK WINDS THIS MORNING: DAMAGING WINDS ARE PEAKING THIS
MORNING AS THE COLD FRONT SAGS SOUTH. POWER OUTAGES ARE ALREADY
OCCURRING, ESPECIALLY ACROSS NORTHWEST MONTANA AND NORTHERN
IDAHO.
- LOWERING SNOW LEVELS: THE ATMOSPHERIC RIVER STALLS TODAY
THROUGH FRIDAY. EXPECT LOWER-THAN-MODELED SNOW LEVELS (DOWN TO
2,500 FEET OR EVEN VALLEY FLOORS IN SPOTS) DUE TO HEAVY
PRECIPITATION RATES CAUSING TOP-DOWN COOLING. THIS WILL CREATE
DIFFICULT WINTRY TRAVEL ALONG AND ROUGHLY 80 MILES NORTH/SOUTH
OF THE I-90 CORRIDOR.
- SOUTHERN RAIN/ROCKFALL: AREAS SOUTH (GRANGEVILLE TO ELK CITY)
WILL REMAIN IN MODERATE TO HEAVY RAIN, ELEVATING THE RISK FOR
ROCKFALLS, SNOW SLOUGHING, AND MINOR RIVER RISES.
- SATURDAY EVENING SQUALL & FREEZE RISK: AN ARCTIC BOUNDARY
MOVING INTO WESTERN MONTANA(70% 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.
- OVERRUNNING SNOW/WARM FRONT SUNDAY NIGHT(80% CHANCE): WINTRY
TRAVEL AGAIN POSSIBLE.
- SPRING TEASE: FOLLOWING A COOL WEEKEND, A MAJOR WARM-UP IS
EXPECTED NEXT WEEK WITH HIGHS REBOUNDING INTO THE 50S AND 60S.
DISCUSSION:
NEAR TERM (TODAY): THE WIND CLIMAX
A HIGHLY COMPLEX SERIES OF EVENTS IS UNFOLDING THROUGH THE
WEEKEND. THE WIDELY ADVERTISED ATMOSPHERIC RIVER AND HIGH WIND
EVENT IS CURRENTLY UNDERWAY. WINDS ALOFT ARE RIPPING AT NEAR
HURRICANE-FORCE. WHILE THE PRE-FRONTAL ENVIRONMENT KEPT MOST OF
THIS ENERGY ALOFT, PRECIPITATION-INDUCED MOUNTAIN WAVE ACTIVITY IS
ALREADY MIXING DAMAGING WINDS TO THE SURFACE ACROSS NORTHWEST
MONTANA, LEADING TO EARLY MORNING POWER OUTAGES AROUND NORTHERN
FLATHEAD LAKE AND NORTHERN IDAHO. MIDNIGHT SOUNDINGS OUT OF
SPOKANE WERE IMPRESSIVE: 69 MPH AT 3,700 FEET MSL AND 81 MPH AT
5,700 FEET MSL. MT. SENTINEL EAST OF MISSOULA IS ALREADY REPORTING
SUSTAINED WINDS OF 51 MPH WITH GUSTS TO 72 MPH—AND WE HAVEN'T
REACHED THE CLIMAX JUST YET.
AS THE WEST-TO-EAST COLD FRONT BEGINS TO SAG SOUTH ACROSS
NORTHWEST MONTANA TOWARDS DAYBREAK, WINDS ALOFT WILL INCREASE IN
RESPONSE, SIGNALING THE PEAK OF OUR DAMAGING MIX-DOWN WINDS
THROUGH THE MORNING HOURS. FLOW ALOFT REMAINS STRONG LATER TODAY,
KEEPING MOUNTAIN RIDGES GUSTING 40 TO 60 MPH AND VALLEYS BREEZY.
ALSO THE MOUNTAINS AND PASSES COULD HAVE BLOWING AND DRIFTING
SNOW. GIVEN THE HEAVY SNOWFALL AND STRONG WINDS, BACKCOUNTRY
RECREATIONISTS ARE STRONGLY ENCOURAGED TO CHECK THEIR LOCAL
AVALANCHE CENTER FORECASTS.
SHORT TERM (TONIGHT - FRIDAY): STALLED ATMOSPHERIC RIVER &
LOWERING SNOW LEVELS
THE AFOREMENTIONED FRONT WILL ESSENTIALLY STALL FROM NORTH-
CENTRAL IDAHO EAST TOWARD GREAT FALLS THROUGH TONIGHT BEFORE
RETREATING NORTH ON FRIDAY. SIMULTANEOUSLY, THE ATMOSPHERIC RIVER
WILL PARK ITSELF OVER THE WA/OR BORDER EASTWARD INTO WEST-CENTRAL
MONTANA.
AS THE EVENT UNFOLDS, IT IS BECOMING CLEAR THAT HEAVY
PRECIPITATION RATES WILL LIKELY DRIVE SNOW LEVELS MUCH LOWER THAN
CURRENT NBM GUIDANCE SUGGESTS DUE TO TOP-DOWN COOLING, SIMILAR TO
THE ATMOSPHERIC RIVER EVENT A WEEK AGO. SNOW LEVELS MAY DROP TO
2,500 FEET FROM CLEARWATER COUNTY EASTWARDS(60% CHANCE), AND MUCH
LOWER TO THE NORTH. IT IS ENTIRELY POSSIBLE SNOW LEVELS NEAR
OROFINO CRASH TO THE VALLEY FLOOR. EXPECT WINTRY TRAVEL ALONG THE
I-90 CORRIDOR AND EXTENDING ROUGHLY 80 MILES NORTH AND SOUTH.
VALLEY LOCATIONS (WESTERN CLEARWATER, SANDERS/MINERAL, MISSOULA,
GRANITE, AND POWELL COUNTIES) COULD RECEIVE 1 TO 4 INCHES OF
MODERATE/HEAVY, WET SNOW TONIGHT THROUGH FRIDAY MORNING.
FURTHER SOUTH TOWARDS GRANGEVILLE AND ELK CITY, PRECIPITATION
WILL PRIMARILY FALL AS MODERATE-TO-HEAVY RAIN, KEEPING THE THREAT
FOR ROCKFALLS AND SNOW SLOUGHING NEAR ROADWAYS ELEVATED.
THE WEEKEND (SATURDAY - SUNDAY): ARCTIC BOUNDARY & RAPID FREEZE
A NORTHWEST-TO-SOUTHEAST MOVING SHORTWAVE TROUGH WILL FINALLY
PUSH THROUGH SATURDAY MORNING, ERODING THE SUBTROPICAL MOISTURE
PLUME. EXPECT A SLUSHY START TO SATURDAY FOR THE AREAS MENTIONED
ABOVE WITH GUSTY POST-FRONTAL WINDS UP TO 35 MPH. THE ATMOSPHERE
BECOMES HIGHLY UNSTABLE BY SATURDAY AFTERNOON, LIKELY BRINGING
MORE SNOW/GRAUPEL SHOWERS TO THE REGION.
FORECAST MODELS HAVE NOTABLY TRENDED COLDER WITH AN ARCTIC
AIRMASS PLUNGING SOUTH OUT OF ALBERTA BY SATURDAY EVENING(70%
CHANCE OF MOVING INTO WESTERN MONTANA). THIS BOUNDARY WILL TAP
INTO THE LINGERING INSTABILITY, AND COULD PRODUCE AN INTENSE
FRONTAL BAND(S) OF HEAVY SNOW SOMEWHERE BETWEEN KALISPELL AND
MISSOULA, AND FROM THE IDAHO BORDER TO POWELL COUNTY. THE TIMING
OF THIS FEATURE IS HIGHLY CONCERNING. MILD DAYTIME TEMPERATURES
AND WET ROADS WILL LIKELY FREEZE RAPIDLY AS HEAVY SNOW FALLS AND
TEMPERATURES DROP, WHICH COULD CREATE INCREDIBLY SLICK AND
DANGEROUS TRAVEL CONDITIONS SATURDAY EVENING. SHOWER ACTIVITY WILL
FINALLY WANE BY MIDNIGHT AS THE FRONT LOSES STEAM.
EXTENDED (SUNDAY - NEXT WEEK): A BRIEF BREAK, THEN SPRING
SUNDAY OFFERS A BRIEF, ALBEIT CHILLY, REPRIEVE. HOWEVER, CLOUDS
WILL QUICKLY INCREASE AS THE NEXT SYSTEM—ASSOCIATED WITH ANOTHER
ATMOSPHERIC RIVER AIMED AT BRITISH COLUMBIA—BEGINS SPREADING
OVERRUNNING MOISTURE INTO THE REGION BY SUNDAY NIGHT. THIS WARM-
FRONT PRECIPITATION WILL LIKELY BRING ANOTHER ROUND OF WINTRY
TRAVEL TO THE MOUNTAINS AND SELECT VALLEYS.
THE LIGHT AT THE END OF THE TUNNEL? A VERY WARM, OCCASIONALLY
DIRTY RIDGE BUILDS IN NEXT WEEK, SENDING TEMPERATURES SOARING BACK
INTO THE 50S AND 60S!
AVIATION
THE POWERFUL ATMOSPHERIC RIVER AND ASSOCIATED COLD
FRONT ARE CURRENTLY DRIVING PEAK WINDS ACROSS THE NORTHERN ROCKIES
THIS MORNING. EXPECT WIDESPREAD SURFACE GUSTS IN EXCESS OF 35-50
KTS AND SIGNIFICANT LOW LEVEL WIND SHEAR (LLWS) TO CONTINUE
THROUGH THE MORNING HOURS BEFORE SURFACE WINDS GRADUALLY TAPER,
THOUGH BREEZY CONDITIONS WILL PERSIST THROUGH THE AFTERNOON.
AS THE FRONTAL BOUNDARY STALLS TODAY INTO FRIDAY, PROLONGED
MODERATE TO HEAVY PRECIPITATION WILL CONTINUE ACROSS THE REGION.
TERMINALS THAT BEGAN WITH RAIN MAY SEE A TRANSITION TO HEAVY, WET
SNOW, RESULTING IN PROLONGED PERIODS OF IFR TO LIFR CONDITIONS DUE
TO LOW CEILINGS AND SNOWFALL. THIS WILL HEAVILY IMPACT KGPI, AND
LIKELY KMSO AS SNOW LEVELS DROP.
LOOKING AHEAD TO SATURDAY, A SECONDARY COLD FRONT WILL BRING
INCREASING INSTABILITY BY THE AFTERNOON, INTRODUCING THE POTENTIAL
FOR CONVECTIVE SNOW AND GRAUPEL SHOWERS AND GUSTY WINDS AT ALL
TERMINALS. BY SATURDAY EVENING, AN ARCTIC BOUNDARY MOVING SOUTH
FROM ALBERTA MAY DEVELOP A BAND OF MODERATE TO HEAVY SNOW,
PARTICULARLY ALONG THE CORRIDOR BETWEEN KGPI AND KMSO, BUT AREAS
FURTHER TO THE EAST TOWARDS MACDONALD PASS COULD ALSO BE AFFECTED.
THESE HEAVIER SNOW SHOWERS WILL LIKELY CAUSE SUDDEN VISIBILITY AND
CEILING REDUCTIONS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING UNTIL NOON MDT SATURDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT REGION...
LOWER CLARK FORK REGION.
HIGH WIND WARNING UNTIL 6 PM MDT THIS EVENING FOR
FLATHEAD/MISSION VALLEYS...KOOTENAI/CABINET REGION...
MISSOULA/BITTERROOT VALLEYS...POTOMAC/SEELEY LAKE REGION.
BLIZZARD WARNING UNTIL 9 AM MDT THIS MORNING FOR WEST GLACIER
REGION.
WINTER STORM WARNING FROM 9 AM THIS MORNING TO NOON MDT SATURDAY
FOR WEST GLACIER REGION.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO NOON MDT SATURDAY
FOR POTOMAC/SEELEY LAKE REGION.
ID...WINTER STORM WARNING UNTIL 11 AM PDT SATURDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
WIND ADVISORY UNTIL 11 AM PDT THIS MORNING FOR LOWER HELLS
CANYON/SALMON RIVER REGION...OROFINO/GRANGEVILLE REGION.
HIGH WIND WARNING UNTIL MIDNIGHT MDT TONIGHT FOR EASTERN LEMHI
COUNTY...WESTERN LEMHI COUNTY.
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