858
FXUS65 KMSO 091758
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1158 AM MDT SAT MAY 9 2026
DISCUSSION
KEY MESSAGES:
- RAPIDLY BUILDING HEAT WILL BRING WIDESPREAD TEMPERATURES IN THE
70S AND 80S THIS WEEKEND. TEMPERATURES MAY REACH NEAR 90 DEGREES
BY TUESDAY.
- DANGEROUSLY COLD WATER IS THE PRIMARY HAZARD. RIVER TEMPERATURES
IN THE 40S AND 50S CAN TRIGGER IMMEDIATE COLD-WATER SHOCK.
A STRONG HIGH-PRESSURE SYSTEM IS BUILDING OVER THE REGION. WE HAVE
HIGH CONFIDENCE THAT DRY AND UNUSUALLY WARM WEATHER WILL LAST
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. TUESDAY AND WEDNESDAY
REMAIN ON TRACK TO BE THE HOTTEST TWO DAYS OF THE SEASON SO FAR.
CURRENT FORECASTS SHOW TEMPERATURES NEARING 90 DEGREES—THERE IS A
25% CHANCE FOR TUESDAY AND A 40% CHANCE FOR WEDNESDAY IN THE
MISSOULA AND BITTERROOT VALLEYS. THE VALLEYS OF THE LOWER CLARK
FORK AND THE KOOTENAI ARE LIKELY TO SEE SIMILAR PROBABILITIES,
WITH A 70% CHANCE FOR THE LOWER IDAHO RIVER VALLEYS. THESE
TEMPERATURES WOULD APPROACH DAILY RECORD HIGHS FOR MANY LOCATIONS.
DESPITE THE SUMMER-LIKE AIR, LOCAL RIVERS AND STREAMS REMAIN
EXTREMELY DANGEROUS. WATERWAYS ARE RUNNING FAST AND HIGH DUE TO
PEAK MOUNTAIN SNOWMELT. DEBRIS AND HAZARDS MAY BE HIDDEN JUST
UNDER THE WATER’S SURFACE. WATER TEMPERATURES BETWEEN 40 AND 50
DEGREES CAN PARALYZE MUSCLES AND TRIGGER AN IMMEDIATE,
UNCONTROLLABLE GASP FOR AIR (COLD-WATER SHOCK) WITHIN MINUTES,
EVEN FOR EXPERIENCED SWIMMERS. ANYONE RECREATING NEAR THE WATER IS
URGED TO WEAR A LIFE JACKET AND STAY BACK FROM SLIPPERY, UNSTABLE
BANKS.
FORECAST CONFIDENCE DECREASES BY THURSDAY AS THE HIGH-PRESSURE
SYSTEM BEGINS TO WEAKEN. THERE IS CURRENTLY A 50% CHANCE OF A
SHIFT TOWARD COOLER WEATHER AND A MORE UNSETTLED PATTERN
(INCREASED CLOUDS AND RAIN) BY THURSDAY. HOWEVER, 20% OF LONG-
RANGE FORECAST MODELS SUGGEST THE HIGH-PRESSURE RIDGE MAY HOLD
UNTIL THE END OF THE WEEK. IN THAT CASE, NEAR-RECORD WARMTH WOULD
CONTINUE.
AVIATION
CLEAR SKIES AND GOOD VISIBILITY (VFR) WILL CONTINUE
ACROSS THE NORTHERN ROCKIES THROUGH THE FORECAST PERIOD. EXPECT
TYPICAL AFTERNOON WINDS FROM THE WEST TO GUST BETWEEN 10 AND 20
KNOTS, THOUGH KALISPELL (GPI) WILL SEE MORE SOUTHERLY WINDS DUE
TO THE FLATHEAD LAKE BREEZE. WINDS WILL BECOME LIGHT AND VARIABLE
OVERNIGHT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page