192
FXUS65 KMSO 311802
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1202 PM MDT TUE MAR 31 2026
DISCUSSION
KEY MESSAGES:
- SIGNIFICANT CLOSED LOW PRESSURE SYSTEM MOVING THROUGH THE REGION
WEDNESDAY NIGHT THROUGH FRIDAY BRINGING WIDESPREAD SNOW AND
COOLER TEMPERATURES.
- HIGH PRESSURE RETURNS THIS WEEKEND, BRINGING WARMING AND DRYING.
THE NORTHERN ROCKIES WILL REMAIN UNDER A MOIST WEST-SOUTHWEST FLOW
THROUGH WEDNESDAY AHEAD OF AN APPROACHING PACIFIC TROUGH. HIGH
MOUNTAIN PASSES SOUTH OF I-90, INCLUDING LOLO, LOST TRAIL, AND
HOMESTAKE, MAY SEE NUISANCE SNOW ACCUMULATIONS THROUGH TONIGHT,
THOUGH IMPACTS WILL REMAIN LOCALIZED. WHILE WIDESPREAD SHOWERS
DEVELOP WEDNESDAY, RISING SNOW LEVELS (5000 TO 6000 FEET) WILL
LIMIT ACCUMULATIONS TO THE HIGHEST TERRAIN.
THE PRIMARY FORECAST CHALLENGE ARRIVES LATE WEDNESDAY NIGHT THROUGH
FRIDAY AS THE TROUGH EVOLVES INTO A CLOSED LOW. WHILE A COLD
FRONT IS EXPECTED TO DROP SNOW LEVELS TO 3000 FEET BY THURSDAY
MORNING, UNCERTAINTY REMAINS REGARDING THE EXACT TRACK AND TIMING
OF THE CLOSED LOW. SMALL LATITUDINAL SHIFTS IN THE CENTER OF THIS
FEATURE WILL DICTATE WHERE THE HEAVIEST PRECIPITATION FALLS.
CURRENT GUIDANCE FAVORS A HEAVY, WET SNOW EVENT FOR THE
SEELEY/SWAN AND BUTTE/BLACKFOOT REGIONS THURSDAY INTO FRIDAY
MORNING, WHERE UPSLOPE FLOW AND WRAP-AROUND MOISTURE ARE MOST
LIKELY TO OVERLAP. GIVEN THE HIGH-MOISTURE CONTENT OF SNOWFALL,
TREE DAMAGE AND POWER OUTAGES ARE A CONCERN. HOWEVER, BECAUSE THE
EXACT POSITION OF THESE HEAVY PRECIPITATION BANDS OFTEN REMAINS
VOLATILE UNTIL 24 HOURS BEFORE ONSET, RESIDENTS AND TRAVELERS
SHOULD ANTICIPATE ADJUSTMENTS TO THE CURRENT WINTER STORM WATCHES.
ON FRIDAY, THE SYSTEM WILL EXIT THE REGION, BRINGING CONTINUED
LIGHT SNOWFALL UNDER NORTHWEST FLOW ALOFT AND COOLER TEMPERATURES.
HIGH CONFIDENCE ( >80%) EXISTS FOR A TRANSITION TO A WARMER,
DRIER REGIME THIS WEEKEND AS A HIGH-PRESSURE RIDGE BUILDS OVER THE
REGION.
AVIATION
THE NORTHERN ROCKIES WILL EXPERIENCE PERIODS OF MOUNTAIN
OBSCURATIONS AND LOCALIZED VALLEY MVFR CONDITIONS THROUGH
WEDNESDAY AS A MOIST WEST-SOUTHWEST FLOW PREVAILS AHEAD OF AN
APPROACHING PACIFIC TROUGH. PRIMARILY SOUTH OF THE I-90 CORRIDOR,
INCLUDING TERMINALS NEAR KMSO AND KBTM, INTERMITTENT LIGHT SNOW
WILL IMPACT MOUNTAIN PASSES THROUGH TONIGHT, THOUGH VALLEY FLOORS
SHOULD REMAIN VFR. BY WEDNESDAY, A MORE WIDESPREAD INCREASE IN
SHOWER ACTIVITY IS EXPECTED; HOWEVER, RISING SNOW LEVELS TO
BETWEEN 5000 AND 6000 FEET WILL TRANSITION MOST TERMINAL IMPACTS
TO RAIN, WITH SNOW-RELATED IFR/LIFR RISKS AND ICING BECOMING
INCREASINGLY CONFINED TO THE HIGHER TERRAIN AND MOUNTAIN CRESTS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH LATE
THURSDAY NIGHT FOR BITTERROOT/SAPPHIRE
MOUNTAINS...BUTTE/BLACKFOOT REGION...POTOMAC/SEELEY LAKE REGION.
ID...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH LATE THURSDAY
NIGHT FOR SOUTHERN CLEARWATER MOUNTAINS.
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