401
FXUS65 KMSO 011843
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1243 PM MDT WED OCT 1 2025
DISCUSSION
KEY MESSAGES:
- BREEZY WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TODAY.
- COOL AND UNSETTLED PATTERN PERSISTS. MORE PRECIPITATION, AND
COLDER, THIS WEEKEND.
- SIGNIFICANT EARLY-SEASON MOUNTAIN SNOW POSSIBLE LATE SATURDAY
INTO SUNDAY WITH EVEN COLDER TEMPERATURES TO FOLLOW.
A BROAD UPPER-LEVEL TROUGH OFF THE PACNW COAST WILL MAINTAIN A
COOL, UNSTABLE SOUTHWEST FLOW ACROSS WESTERN MONTANA AND NORTH-
CENTRAL IDAHO INTO THE LATE-WEEK. EMBEDDED SHORTWAVES ROTATING
THROUGH THE TROUGH WILL TRIGGER INTERMITTENT SHOWERS AND ISOLATED
THUNDERSTORMS, PARTICULARLY DURING PEAK DAYTIME HEATING IN THE
AFTERNOON AND EARLY EVENING. THE MAIN THREATS FROM ANY STRONGER
STORMS THIS AFTERNOON WILL BE BRIEFLY HEAVY RAINFALL, AND HAIL UP
TO 3/4" IN SIZE.
AN APPROACHING UPPER-LEVEL JET STREAK WILL INCREASE WINDS ALOFT
THIS AFTERNOON AND EVENING, RESULTING IN BREEZY WINDS AT THE
SURFACE. WIDESPREAD SOUTHWESTERLY GUSTS UP TO 20 MPH ARE EXPECTED,
WITH LOCALIZED GUSTS TO 30 MPH POSSIBLE (60% CHANCE) ALONG
RIDGETOPS NEAR THE CONTINENTAL DIVIDE AND ACROSS SOUTHWEST
MONTANA, THE BITTERROOTS, AND IDAHO/LEMHI COUNTIES.
THE UPPER-LEVEL PATTERN EVOLVES THIS WEEKEND AS THE BROAD TROUGH
BEGINS TO CUT OFF AND DROP SOUTHWARD INTO THE GREAT BASIN. RECENT
TRENDS IN MODEL GUIDANCE NOW FAVOR A TRACK NORTHWARD OUT OF THE
GREAT BASIN AND INTO WYOMING BY THE WEEKEND AS THE CUT OFF LOW
ATTEMPTS TO REJOIN THE PREVAILING WESTERLIES. THIS WILL LIKELY
COINCIDE WITH A PLUME OF MARITIME MOISTURE AND AN UPTICK IN
PERSISTENCE, AND AMOUNTS, OF PRECIPITATION ACROSS SOUTHWEST
MONTANA AND LEMHI COUNTY. INITIALLY, SNOW LEVELS WILL REMAIN HIGH,
NEAR 7,000FT.
CONFIDENCE REMAINS MODERATELY HIGH IN A SECONDARY, COLDER TROUGH
DIGGING SOUTH FROM CANADA SATURDAY INTO SUNDAY ACCOMPANIED BY A
DEEP POOL OF COLD AIR SLIDING SOUTHWARD ALONG AND EAST OF THE
CONTINENTAL DIVIDE. SNOW LEVELS UNDER THIS SCENARIO WOULD LIKELY
LOWER TO NEAR 5000 FEET IN THIS AREA BY SUNDAY MORNING.
PROBABILISTIC GUIDANCE DERIVED FROM THE NBM INDICATES ABOUT A 40%
CHANCE OF AT LEAST 1 INCH OF SNOW, AND ABOUT A 10% CHANCE FOR 6
INCHES OR MORE FOR ELEVATIONS ABOVE 6,000 FT IN GLACIER NATIONAL
PARK. HIGH-ELEVATION AND BACKCOUNTRY USERS SHOULD PREPARE FOR
COLD, WET, AND WINDY CONDITIONS THIS WEEKEND WITH INCREASED RISK
FOR HYPOTHERMIA AND FROSTBITE. GOING-TO-THE-SUN ROAD, AND OTHER
HIGH-ELEVATION FOREST SERVICE ROADS, MAY BECOME SNOW OR SLUSH
COVERED MAKING TRAVEL POTENTIALLY DIFFICULT/HAZARDOUS AT TIMES
THROUGH THE WEEKEND.
AVIATION
LOWER MID-LEVEL BROKEN CLOUD COVER IS EXPECTED TO
REMAIN THROUGH THE AFTERNOON AND EVENING WITH SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS WITH BRIEF HEAVY RAIN AND POTENTIAL FOR
HAIL. LOWERED CEILINGS AND TERRAIN OBSCURATIONS BECOMING
INCREASINGLY WIDESPREAD THROUGH THE REST OF THE DAY. SOUTHWESTERLY
WINDS GUSTING TO 20 KNOTS AT TIMES DURING THE AFTERNOON,
ESPECIALLY NEAR KSMN/KBTM, AND RIDGETOPS GUSTING TO 30 KNOTS.
ANOTHER CHANCE FOR LOW-STRATUS AND FOG INTO THE OVERNIGHT AND
EARLY MORNING HOURS TOMORROW.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page