675
FXUS65 KMSO 261854
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1254 PM MDT WED AUG 26 2026
DISCUSSION
KEY MESSAGES:
- SCATTERED THUNDERSTORMS TODAY INTO THURSDAY, WITH LIGHTNING AND
OUTFLOW WINDS BEING THE MAIN THREATS.
- A COLD FRONT ARRIVES SATURDAY, BRINGING COOLING TEMPERATURES,
GUSTY WESTERLY WINDS, AND PRECIPITATION, FOCUSED ALONG AND
SOUTH OF I-90.
THE NORTHERN ROCKIES WILL BE UNDER THE INFLUENCE OF A
SOUTHWESTERLY FLOW PATTERN ALOFT THROUGH FRIDAY. THIS PATTERN IS
BEING DRIVEN BY A RIDGE OF HIGH PRESSURE CENTERED OVER THE FOUR
CORNERS REGION AND A TROUGH OF LOW PRESSURE CENTERED OVER SOUTHERN
BRITISH COLUMBIA. WAVES OF MONSOON MOISTURE WILL BRING MODEST
MOISTURE AND INSTABILITY INTO THE AREA, OPENING THE DOOR FOR
SHOWERS AND THUNDERSTORMS EACH DAY. WARM AND DRY AIR NEAR THE
SURFACE WILL PROMOTE GUSTY TO STRONG (30-50 MPH) OUTFLOW WIND
GUSTS. THE COMBINATION OF DRY STORMS, LIGHTNING, AND GUSTY WINDS
WILL ELEVATE THE POTENTIAL FOR NEW FIRE STARTS. THE THUNDERSTORM
THREAT WILL INCLUDE ALL OF THE NORTHERN ROCKIES THIS AFTERNOON
AND EVENING, WITH ACTIVITY SHIFTING INTO LEMHI COUNTY, ID AND
SOUTHWEST MONTANA ON THURSDAY. A RED FLAG WARNING IS IN EFFECT FOR
THE PALOUSE/HELLS CANYON REGION, WHERE HOT, DRY, AND WINDY
CONDITIONS ARE EXPECTED THIS AFTERNOON AND EVENING.
FORECAST MODELS HAVE COME INTO STRONGER AGREEMENT FOR THE
AFOREMENTIONED TROUGH TO PUSH EASTWARD ACROSS THE PACIFIC
NORTHWEST INTO THE NORTHERN ROCKIES BY LATE SATURDAY INTO SUNDAY.
A SUBTLE DROP IN TEMPERATURES ARRIVES FRIDAY, WITH TEMPERATURES
DROPPING FURTHER ON SATURDAY AS A COLD FRONT MOVES THROUGH THE
REGION. WHILE MODEL SOLUTIONS STILL DIFFER ON THE EVOLUTION OF THE
TROUGH AND MOISTURE AVAILABILITY FOR PRECIPITATION, THE
PROBABILITY FOR WETTING RAINS HAS INCREASED FROM 30-40%
(YESTERDAY) TO 70-80% THIS WEEKEND FOR AREAS ALONG AND SOUTH OF
I-90. GENERALLY SPEAKING, PROBABILITIES FOR PRECIPITATION DECREASE
FURTHER NORTH TOWARDS THE US-CANADIAN BORDER. WAVES OF MONSOON
MOISTURE WILL FOCUS ATMOSPHERIC MOISTURE AND INSTABILITY ALONG AND
SOUTH OF I-90, DRIVING HIGHER CHANCES FOR SHOWERS AND
THUNDERSTORMS AS THE TROUGH ARRIVES. THIS MOISTURE WILL LIMIT THE
POTENTIAL FOR CRITICAL FIRE WEATHER.
AVIATION
AFTERNOON AND EVENING THUNDERSTORMS WILL BE THE
PRIMARY IMPACT TO AVIATION TODAY AND THURSDAY. CONVECTION WILL
INITIALLY DEVELOP AROUND 26/2100Z NEAR KSMN AND KBTM, EVENTUALLY
SPREADING NORTHWARD TOWARD KMSO, KHRF, AND KGPI THIS EVENING. THE
PRIMARY AVIATION HAZARDS WITH THESE HIGH-BASED STORMS WILL BE
LOCALIZED, ERRATIC OUTFLOW WIND GUSTS OF 30 TO 40 KNOTS. LOCALIZED
GUSTS TO 50 KTS ARE A CONCERN NEAR THE STRONGEST THUNDERSTORMS
TODAY. FLIGHT CATEGORIES WILL LARGELY REMAIN VFR, THOUGH BRIEF
MVFR CONDITIONS AND LOCALIZED MOUNTAIN OBSCURATIONS ARE EXPECTED
DURING DIRECT THUNDERSTORM IMPACTS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...RED FLAG WARNING UNTIL 7 PM PDT THIS EVENING FOR PALOUSE/HELLS
CANYON.
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