482
FXUS65 KMSO 132023
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
223 PM MDT FRI MAR 13 2026
DISCUSSION
KEY MESSAGES:
- ADDITIONAL VALLEY SNOW TONIGHT: STEADY SNOW IS EXPECTED THROUGH
THE FLATHEAD AND MISSION VALLEYS TONIGHT. SNOW IS AGAIN
POSSIBLE IN THE MISSOULA AND NORTHERN BITTERROOT VALLEYS
TONIGHT BUT LESS CERTAIN WITH SLIGHTLY WARMER TEMPERATURES.
- INTENSE SATURDAY SNOW SQUALLS: HIGH-IMPACT SNOW SQUALLS AND A
FLASH-FREEZE POSSIBLE ACROSS NORTHWEST AND WEST-CENTRAL
MONTANA SATURDAY AFTERNOON AND EVENING.
THE PRIMARY FORECAST CHALLENGE TONIGHT REMAINS THE PRECISE
LOWERING OF SNOW LEVELS AS HEAVY PRECIPITATION RATES CONTINUE TO
DRIVE TOP-DOWN COOLING ACROSS THE REGION. CONSISTENT SNOW IS
EXPECTED TO DEVELOP AND PERSIST THROUGH THE NIGHT FOR THE FLATHEAD
AND MISSION VALLEYS. RESIDENTS SHOULD EXPECT SEVERAL INCHES OF
ACCUMULATION BY DAYBREAK SATURDAY. AS THE NIGHT PROGRESSES, THE
STEADY NATURE OF THE SNOW WILL BEGIN TO TRANSITION INTO MORE
INTENSE, CELLULAR SHOWERS AS THE ATMOSPHERE DESTABILIZES AHEAD OF
THE ARRIVING SHORTWAVE.
THE OVERALL AIRMASS IS SLIGHTLY WARMER THIS AFTERNOON, MEANING
THAT WHILE RAIN IS EXPECTED TO CHANGE BACK TO SNOW IN THE
MISSOULA AND NORTHERN BITTERROOT VALLEYS TONIGHT, ACCUMULATING
SNOW ON PAVED SURFACES WILL BE MORE DIFFICULT TO ACHIEVE. SLUSHY
CONDITIONS ARE THE MOST LIKELY IMPACT ON ROADS. HOWEVER, ANY
HIGHER INTENSITY BURSTS COULD STILL LEAD TO QUICK, TEMPORARY
ACCUMULATIONS BEFORE THE MORE SIGNIFICANT FRONT ARRIVES SATURDAY
AFTERNOON.
CONFIDENCE IS HIGH THAT A FRONTAL BOUNDARY WILL PLUNGE SOUTH OUT
OF ALBERTA SATURDAY MORNING, REACHING NORTHWEST MONTANA BY MIDDAY
AND SURGING THROUGH WEST-CENTRAL MONTANA DURING THE AFTERNOON.
THIS SETUP IS HIGHLY FAVORABLE FOR THE DEVELOPMENT OF FRONTAL SNOW
SQUALLS. THERE IS A 80 PERCENT CHANCE THAT INTENSE BANDS OF SNOW
WILL IMPACT THE CORRIDOR BETWEEN KALISPELL AND MISSOULA AND ALONG
HIGHWAY 200. THE TIMING IS PARTICULARLY CONCERNING FOR I-90 FROM
LOOKOUT PASS TO HOMESTAKE PASS; A PERIOD OF HEAVY SNOW, GUSTY
WINDS UP TO 45 MPH, AND RAPIDLY DROPPING TEMPERATURES IS LIKELY.
ANY ROADS WET FROM EARLIER DAYTIME MELTING WILL BE PRONE TO A
"FLASH FREEZE," CREATING TREACHEROUS AND UNPREDICTABLE TRAVEL
CONDITIONS THROUGH SATURDAY NIGHT.
CONDITIONS WILL BRIEFLY STABILIZE ON SUNDAY AS A ARCTIC AIR MASS
SETTLES IN THE REGION. BY SUNDAY NIGHT, OVERRUNNING MOISTURE FROM
A NEW PACIFIC SYSTEM WILL REINTRODUCE WINTRY TRAVEL CONCERNS,
PARTICULARLY FOR THE MOUNTAINS AND NORTHERN VALLEYS.
LOOKING FURTHER AHEAD, ENSEMBLE GUIDANCE STRONGLY FAVORS A SHIFT
TOWARD A HIGH-AMPLITUDE RIDGE STARTING TUESDAY. WHILE SOME "DIRTY"
RIDGE CLOUD COVER REMAINS POSSIBLE, A SIGNIFICANT WARMING TREND
WILL TAKE HOLD MID-WEEK, WITH VALLEY HIGH TEMPERATURES POTENTIALLY
REBOUNDING INTO THE 50S AND 60S BY NEXT FRIDAY.
AVIATION
TEMPERATURES ARE SLOWLY MODERATING IN THE VALLEYS THIS
AFTERNOON WITH PLACES LIKE KMSO SWITCHING TO A RAIN OR RAIN/SNOW
MIX. THERE ARE INDICATIONS THAT SNOW LEVELS WILL LOWER OVERNIGHT
TO NEAR MOST VALLEY FLOORS IN WESTERN MONTANA. SNOW IS LIKELY TO
CONTINUE IN NORTHWEST MONTANA WITH LONG-DURATION IFR CONDITIONS,
INCLUDING AT KGPI. WIDESPREAD MVFR/IFR CONDITIONS WILL PREVAIL
ACROSS THE REGION AS CONSISTENT PRECIPITATION REDUCES VISIBILITY
AND CEILINGS. TERRAIN WILL REMAIN OBSCURED ACROSS ALL NORTH-
CENTRAL IDAHO AND WESTERN MONTANA RANGES. A TROUGH PASSAGE ON
SATURDAY WILL TRANSITION PRECIPITATION TO INTENSE SNOW SHOWERS
DURING SATURDAY MORNING, FOLLOWED BY A LINE OF INTENSE SNOW
SQUALLS (LIFR LIKELY) AND ERRATIC WINDS ALONG THE HIGHWAY 200 AND
I-90 CORRIDOR FROM SATURDAY AFTERNOON THROUGH SATURDAY NIGHT.
THESE SQUALLS ARE LIKELY TO IMPACT KMSO AND KBTM, CAUSING SUDDEN
WHITEOUT CONDITIONS AND POTENTIAL FOR RAPID SURFACE ICING.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING UNTIL NOON MDT SATURDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...LOWER CLARK FORK REGION...
POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 6 PM MDT
SATURDAY FOR FLATHEAD/MISSION VALLEYS.
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT SATURDAY NIGHT FOR
BUTTE/BLACKFOOT REGION.
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.
WIND ADVISORY FROM NOON TO 9 PM MDT SATURDAY FOR EASTERN LEMHI
COUNTY...WESTERN LEMHI COUNTY.
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