764
FXUS65 KMSO 121851
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1251 PM MDT TUE MAY 12 2026
DISCUSSION
KEY MESSAGES:
- NEAR-RECORD HEAT TODAY: HIGHS WILL REACH THE 80S TO LOW 90S.
RIVERS REMAIN DANGEROUSLY COLD AND FAST; USE EXTREME CAUTION
NEAR THE WATER.
- TWO DISTINCT WIND THREATS WEDNESDAY:
1. DAMAGING THUNDERSTORM WINDS: GUSTS OVER 60 MPH ARE POSSIBLE
WEDNESDAY AFTERNOON, MAINLY FROM DEER LODGE TO BUTTE AND
SOUTHWARD.
2. STRONG COLD FRONT WINDS: GUSTY WINDS WILL ARRIVE WEDNESDAY
AFTERNOON AND EVENING, CREATING DANGEROUS CONDITIONS
FOR BOATERS ON LAKES AND INCREASING FIRE DANGER IN
SOUTHWEST MONTANA.
- DRASTIC TEMPERATURE DROP AND HYPOTHERMIA RISK: SUMMER
CONDITIONS END WEDNESDAY NIGHT. MOUNTAIN HIGHS WILL CRASH INTO
THE 40S ON THURSDAY AND THE 30S THIS WEEKEND WITH ACCUMULATING
SNOW. BACKCOUNTRY USERS MUST PREPARE FOR WINTER CONDITIONS.
FROST IS POSSIBLE BY SUNDAY MORNING.
TODAY (TUESDAY):HIGH PRESSURE BRINGS ONE LAST DAY OF NEAR-RECORD
HEAT, WITH HIGHS IN THE 80S AND LOW 90S. RAPID SNOWMELT CONTINUES
TO KEEP RIVERS DANGEROUSLY COLD. COLD WATER SHOCK IS A SEVERE
HAZARD FOR ANYONE ON THE WATER TODAY; EVEN STRONG SWIMMERS CAN BE
QUICKLY INCAPACITATED BY THESE TEMPERATURES.
WEDNESDAY AND THURSDAY (THE BIG TRANSITION):WEATHER CONDITIONS
WILL CHANGE ABRUPTLY ON WEDNESDAY AS A STRONG COLD FRONT MOVES
THROUGH. MISSOULA AND KALISPELL WILL LIKELY SEE THEIR WARMEST
TEMPERATURES EARLY IN THE DAY BEFORE READINGS BEGIN TO FALL. THE
FRONT IS EXPECTED TO REACH THE CAMAS PRAIRIE IN IDAHO BY MID-
MORNING, WEST-CENTRAL MONTANA BY EARLY AFTERNOON, AND THE BUTTE
AREA BETWEEN 6:00 P.M. AND 9:00 P.M. MDT.
THE DUAL WIND THREAT:
COLD FRONT: WIND IS THE PRIMARY HAZARD ON WEDNESDAY. WHILE SCATTERED
STORMS ARE POSSIBLE, A RAPID INCREASE IN AIR PRESSURE BEHIND THE
FRONT WILL CAUSE WESTERLY WIND GUSTS OF 35 TO 45 MPH. THESE WINDS
WILL CREATE DANGEROUS WAVES FOR SMALL BOATS ON FLATHEAD LAKE AND
OTHER AREA WATERS. EXPECT SOME BROKEN TREE BRANCHES AND ISOLATED
POWER OUTAGES.
THUNDERSTORMS: SHOWERS AND STORMS WILL FORM AS EARLY AS NOON OVER
LEMHI COUNTY, MOVING NORTHEAST AT 30 TO 45 MPH. BECAUSE THE AIR IS
SO DRY, THESE STORMS COULD PRODUCE INTENSE, DAMAGING WIND GUSTS.
THE HIGHEST RISK IS ALONG HIGHWAY 93 IN THE BITTERROOT AND
MISSOULA VALLEYS, EXTENDING EAST TO THE CONTINENTAL DIVIDE. THIS
WILL CREATE DANGEROUS CROSS-WINDS ON NORTH-SOUTH HIGHWAYS AND
INCREASE FIRE DANGER IN SOUTHWEST MONTANA.
THE RAIN/SNOW SHIFT: RAIN AND SNOW WILL FOCUS PRIMARILY ON THE
NORTHERN TWO-THIRDS OF THE REGION LATE WEDNESDAY. VALLEYS MAY SEE
UP TO 0.30 INCHES OF RAIN, WHILE MOUNTAINS COULD RECEIVE UP TO
0.75 INCHES OF LIQUID. AS A COLD STORM SYSTEM MOVES OVER THE AREA,
SNOW LEVELS WILL DROP TO NEAR 5,000 FEET. SEVERAL INCHES OF NEW
SNOW ARE EXPECTED IN THE HIGH COUNTRY OF NORTHWEST MONTANA BY
THURSDAY MORNING. BACKCOUNTRY USERS WILL ENCOUNTER SLUSHY SNOW ON
HIGH-ELEVATION ROADS. COMBINED WITH WINDS AND TEMPERATURES IN THE
40S, THIS CREATES A HIGH RISK FOR HYPOTHERMIA.
FRIDAY THROUGH THE WEEKEND (RETURN TO WINTER): AN UNUSUALLY
STRONG STORM SYSTEM FROM THE GULF OF ALASKA WILL SETTLE OVER THE
NORTHERN ROCKIES THIS WEEKEND. BITTERLY COLD AIR WILL DROP SNOW
LEVELS TO 4,000 FEET. MOUNTAIN HIGHS WILL STAY IN THE 30S, WHILE
VALLEYS WILL STRUGGLE TO REACH THE 50S—ABOUT 15 DEGREES BELOW
NORMAL. UNSTABLE AIR WILL TRIGGER WIDESPREAD SHOWERS ALL WEEKEND.
IN THE VALLEYS, HEAVY BURSTS OF SOFT HAIL (GRAUPEL) ARE POSSIBLE.
BOTTOM LINE FOR THE WEEKEND: PACK FOR WINTER IF YOU ARE HEADING
OUTDOORS. THE COMBINATION OF WET SNOW, WIND, AND NEAR-FREEZING
TEMPERATURES IS DANGEROUS FOR THOSE ONLY PREPARED FOR SPRING. BY
SUNDAY AND MONDAY MORNING, TEMPERATURES MAY DROP LOW ENOUGH TO
CAUSE FROST, WHICH COULD DAMAGE SENSITIVE PLANTS.
AVIATION...CLEAR SKIES AND UNSEASONABLE HEAT CONTINUE THROUGH
TUESDAY WITH LIGHT WINDS. A DRAMATIC CHANGE ARRIVES WEDNESDAY AS A
STRONG COLD FRONT BRINGS SHARP WIND SHIFTS AND SHOWERS.
THUNDERSTORM WIND GUSTS UP TO 45 KNOTS ARE POSSIBLE AT KSMN AND
OVER 50 KNOTS AT KBTM BETWEEN NOON AND 6:00 P.M. WEDNESDAY. SNOW
IN THE MOUNTAINS OF NORTHWEST MONTANA WILL CAUSE CLOUDS TO COVER
THE PEAKS (MOUNTAIN OBSCURATION) WEDNESDAY NIGHT, ESPECIALLY IN
THE GLACIER NATIONAL PARK REGION.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WIND ADVISORY FROM 9 AM WEDNESDAY TO MIDNIGHT MDT WEDNESDAY
NIGHT FOR KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION.
WIND ADVISORY FROM NOON WEDNESDAY TO MIDNIGHT MDT WEDNESDAY
NIGHT FOR BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT
REGION...FLATHEAD/MISSION VALLEYS...MISSOULA/BITTERROOT
VALLEYS...POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 3 PM
MDT THURSDAY FOR WEST GLACIER REGION.
RED FLAG WARNING FROM NOON TO 9 PM MDT WEDNESDAY FOR
DEERLODGE/WEST BEAVERHEAD...EAST BEAVERHEAD.
ID...NONE.
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