834
FXUS65 KMSO 211934
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
134 PM MDT WED OCT 21 2026
DISCUSSION
KEY MESSAGES:
- MILD DAYTIME TEMPERATURES THROUGH THURSDAY.
- PATCHY VALLEY FOG AROUND SUNRISE EACH MORNING.
- SIGNIFICANT WEATHER CHANGE COMING THURSDAY NIGHT INTO FRIDAY.
ENJOY THE UNSEASONABLE WARMTH AS IT WILL CONTINUE THROUGH
THURSDAY. DUE TO STRONG VALLEY INVERSIONS CAUSING STABILITY,
TOMORROW MORNING WILL AGAIN GIVE US A CHANCE FOR PATCHY VALLEY
FOG.
LATE THURSDAY AFTERNOON AN AREA OF SHOWERS MOVES UP FROM THE
SOUTH. A THUNDERSTORM OR TWO WILL BE POSSIBLE, ESPECIALLY IN
SOUTHERN CLEARWATER AND WESTERN LEMHI COUNTIES, ALONG WITH LOST
TRAIL PASS AND POTENTIALLY AS FAR NORTH AS THE SOUTHERN
BITTERROOT VALLEY. THIS AREA OF SHOWERS AND THUNDERSTORMS WILL
BECOME JUST SHOWERS AFTER 7-8 PM AS AFTERNOON HEATING QUICKLY
DISSIPATES. CLOUD COVER HOWEVER WILL KEEP OVERNIGHT TEMPERATURES
QUITE WARM FOR THIS TIME OF YEAR, WITH WIDESPREAD 40-50S AS LOWS,
EXCEPT ALONG THE CONTINENTAL DIVIDE WHERE OVERNIGHT TEMPERATURES
MAY LOWER INTO THE 30S.
A STRONG COLD FRONT MOVES THROUGH THE REGION THURSDAY NIGHT INTO
FRIDAY, BRINGING WIDESPREAD PRECIPITATION OF UP TO 0.10 INCH BUT
SOME AREAS SOUTH AND EAST OF MISSOULA COULD RECEIVE UP TO 0.50
INCH. MOST PRECIPITATION WILL WIND DOWN BY 6 PM FRIDAY EVENING.
ONE NOTABLE LOCATION IS HOMESTAKE PASS AND MACDONALD PASS NEAR
BUTTE, WHERE PRECIPITATION MAY LINGER BETWEEN 6 PM AND MIDNIGHT.
RAPIDLY DROPPING TEMPERATURES COULD COMBINE WITH LIGHT
PRECIPITATION TO PRODUCE A SLUSHY ACCUMULATION, LEADING TO THE
POTENTIAL FOR A BRIEF PERIOD OF WINTER DRIVING CONDITIONS AT THESE
LOCATIONS.
THE UNCERTAINTY SATURDAY ONWARD REMAINS IN THE WEATHER MODELS. THE
NBM FORECAST HAS TEMPERATURES NEAR NORMAL WITH A SPREAD OF UP TO 5
DEGREES ABOVE OR BELOW NORMAL. WITH A FEW PERIODS OF LIGHT
PRECIPITATION, INCLUDING THE POTENTIAL OF FLURRIES OR LIGHT SNOW
SHOWERS IN WESTERN MT VALLEYS. MORE TO COME AS THE FORECAST
EVOLVES.
AVIATION
HIGH PRESSURE WILL CONTINUE TO BRING STABLE
CONDITIONS. A WEAK SOUTHERLY GRADIENT MAY TURN LIGHT WINDS BRIEFLY
SOUTHERLY THIS AFTERNOON BEFORE BECOMING TERRAIN DRIVEN AGAIN
TONIGHT. VALLEY INVERSIONS AND COLD AIR POOLS WILL SET THE STAGE
FOR PATCHY AREAS OF VALLEY FOG, PARTICULARLY NEAR LARGE BODIES OF
WATER AND RIVER SYSTEMS. THE PRIMARY PERIOD TO WATCH WILL BE FROM
22/1000-1500Z, INCLUDING KGPI AND KMSO. THE PROBABILITY OF DENSE
FOG IMPACTS AT THESE TERMINALS IS GENERALLY LESS THAN 10 PERCENT,
BUT CAN NOT BE RULED OUT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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