568
FXUS65 KMSO 100835
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
235 AM MDT TUE MAR 10 2026
DISCUSSION
KEY MESSAGES:
- LONG DURATION ATMOSPHERIC RIVER EVENT WEDNESDAY NIGHT INTO
SATURDAY.
- VERY DIFFICULT BACKCOUNTRY CONDITIONS WITH STRONG WINDS AND
HEAVY SNOW, LEADING TO AREAS OF BLIZZARD CONDITIONS.
- RISK FOR STRONG, LOCALLY DAMAGING WINDS THURSDAY, FOCUSED ACROSS
NORTHWEST MONTANA AND ALONG THE DIVIDE.
BREEZY WEST WINDS AND LIGHT SHOWERS THROUGHOUT TODAY WITH BELOW
NORMAL TEMPERATURES IS FORECAST.
LATE WEDNESDAY THROUGH SATURDAY, A LONG DURATION HIGH INTENSITY
ATMOSPHERIC RIVER EVENT IS ON TRACK TO AFFECT THE NORTHERN
ROCKIES. STRONG TO DAMAGING WINDS THROUGHOUT THURSDAY MORNING ARE
EXPECTED IN WESTERN MT. WIDESPREAD 50 TO 100% PROBABILITIES OF
WIND GUST 50 MPH OR STRONGER ARE FORECAST IN WESTERN MT, VALLEYS
ORIENTATED NORTHWEST TO SOUTHEAST HAVE LOWER PROBABILITIES, 20 TO
50%. EVERY MOUNTAIN RANGE HAS A 50 TO 70% PROBABILITY OF GUSTING
60 MPH OR STRONGER, THERE WILL LOCALIZED GUSTS AS HIGH AS 80 MPH.
WINDS WILL BE SLIGHTLY WEAKER IN NORTH- CENTRAL ID BUT STRONG
WINDS ARE STILL FORECAST. WATCH FOR TREE DAMAGE AND POTENTIAL
POWER OUTAGES FROM THE WINDS.
THIS WILL BE A VERY WET SYSTEM. AS WITH MOST ATMOSPHERIC RIVERS
THEY ORIGINATE IN THE SUBTROPICS AND ARE WARM SYSTEMS. WEDNESDAY
SNOW LEVELS QUICKLY RISE TO AROUND 5000 FEET AND REMAIN THERE
THROUGH SATURDAY I-90 AND SOUTH. SNOW LEVELS NORTH OF I-90 WILL
BE ROUGHLY 1000 FEET LOWER. SPECIFIC SNOW FORECASTS, EVEN AT THIS
TIME FRAME, WILL NOT BE RELIABLE. HOWEVER, 3 TO 6 FEET OF SNOW IN
THE HIGHEST ELEVATIONS OF THE CLEARWATER, BITTERROOT, AND MISSION
MOUNTAINS INCLUDING ALMOST ALL RANGES OF NORTHWEST MONTANA IS
MODERATE PROBABILITY. TRAVEL OR RECREATION IN THE BACK COUNTRY
DURING THIS TIMEFRAME WILL BE DANGEROUS TO IMPOSSIBLE, EXPECT
BLIZZARD CONDITIONS AT TIMES, DOWNED TREES, AND FEET OF HEAVY, WET
SNOW. PLEASE CHECK ROAD REPORTS AND FOLLOW LOCAL AVALANCHE CENTER
GUIDANCE. TYPICAL AREAS FOR ROCK SLIDES; US-12 EITHER SIDE OF LOLO
PASS, I-90 VICINITY OF LOOKOUT PASS, US-200 EAST OF MISSOULA, AND
US-93 EITHER SIDE OF LOST TRAIL PASS, ARE ALREADY EXPERIENCING
ROCK SLIDES. THIS TREND WILL NOT IMPROVE THROUGH THE WEEKEND.
VALLEYS WILL BE TRICKIER: IF THE WIND FORECAST MATERIALIZES,
STORM TOTAL PRECIPITATION WILL LIKELY VERIFY AT THE 25TH
PERCENTILE DUE TO SEVERE VALLEY DOWNSLOPING, WIDESPREAD 0.50 TO
0.75" OVER 72 HOURS WOULD BE REASONABLE. CONVERSELY, IF
PRECIPITATION VERIFIES AT THE 75TH OR HIGH PERCENTILE, 1 TO 2" OF
RAIN, THEN WINDS WILL LIKELY BE SUBDUED BY MODERATE PRECIPITATION
RATES. LEMHI COUNTY ID AND IN THE VICINITY OF BUTTE HAVE THE
LOWEST PRECIPITATION TOTALS IN THE CURRENT FORECAST. WHILE TYPICAL
LOW LYING AND POOR DRAINAGE AREAS WILL BE SUSCEPTIBLE TO PONDING
OF WATER, NO RIVERS ARE CURRENTLY FORECAST TO REACH ACTION STAGE
OR HIGHER.
PLEASE KEEP APPRISED OF FUTURE FORECASTS IN CASE POTENTIAL
IMPACTS CHANGE.
THE ACTIVE WEATHER WILL CONTINUE THROUGHOUT THE WEEKEND AND INTO
EARLY NEXT WEEK WITH LESS INTENSITY.
AVIATION
A STRONG JET STREAM OVER THE REGION IN ZONAL FLOW IS
HELPING TO DRIVE STRONG, GUSTY, WESTERLY WINDS. THE LONGER DAYS
AND HIGHER SUN ANGLE AS WE APPROACH THE EQUINOX ARE ALSO HELPING
TO DESTABILIZE THE BOUNDARY LAYER. AS A RESULT, SOME SHOWERS ARE
TRYING TO FORM IN THE REGION, BUT THE WIND SHEAR IS SO STRONG
COMPARED TO THE INSTABILITY THAT IT KEEPS TEARING THE UPDRAFTS
APART BEFORE THEY CAN ORGANIZE. THE RESULT HAS BEEN, AND WILL
CONTINUE TO BE VERY LIGHT SHOWERS WITH SPRINKLES OR FLURRIES AND
VISIBILITY REDUCTIONS DOWN TO 6SM AT TIMES. THE BIGGEST IMPACT
FOR AVIATION THROUGH THIS EVENING WILL CONTINUE TO BE STRONG WIND
GUSTS AND WIND SHEAR.
LATE WEDNESDAY THROUGH SATURDAY, THE NORTHERN ROCKIES AIRSPACE
WILL BE IMPACTED BY A HIGH INTENSITY ATMOSPHERIC RIVER SYSTEM.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH SATURDAY
MORNING FOR BITTERROOT/SAPPHIRE MOUNTAINS...WEST GLACIER
REGION.
HIGH WIND WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY MORNING
FOR KOOTENAI/CABINET REGION.
HIGH WIND WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
MORNING FOR LOWER CLARK FORK REGION.
HIGH WIND WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
EVENING FOR BUTTE/BLACKFOOT REGION.
ID...WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH SATURDAY
MORNING FOR SOUTHERN CLEARWATER MOUNTAINS.
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