148
FXUS65 KMSO 021611
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1011 AM MDT WED SEP 2 2026
DISCUSSION
KEY MESSAGES:
- WIDESPREAD SHOWERS AND THUNDERSTORMS TODAY WITH OUTFLOW GUSTS
OF 25-45 MPH AND HEAVY RAIN RATES UP TO 0.5 INCH PER HOUR
AN UPPER LEVEL DISTURBANCE AND ASSOCIATED COLD FRONT TRACKING
ACROSS THE NORTHERN ROCKIES HAS ALREADY INITIATED SHOWERS AND
THUNDERSTORMS OVER NORTH-CENTRAL IDAHO THIS MORNING, AND WILL
PROGRESS NORTHEASTWARD ACROSS THE CONTINENTAL DIVIDE BY MID-
AFTERNOON (3-4PM MDT). PRIMARY HAZARDS INCLUDE BRIEF HEAVY
RAINFALL AND ERRATIC OUTFLOW GUSTS OF 30-50 MPH, WITH A 5 TO 10
PERCENT PROBABILITY OF SEVERE GUSTS IN NORTHWEST MONTANA AND ALONG
THE DIVIDE. RECENT HIGH RESOLUTION MODELS ALSO SHOW STRONGER
CELLS CAPABLE OF HAIL AND NEAR SEVERE WINDS FROM LEMHI COUNTY
NORTHEAST THROUGH SILVER BOW COUNTY, MOST LIKELY BETWEEN 1PM AND
3PM MDT.
WHILE WINDS WILL GENERALLY SUBSIDE FOLLOWING THE FRONTAL PASSAGE,
ELEVATED GRADIENT WINDS WILL PERSIST THROUGH SUNSET ACROSS LEMHI
COUNTY AND SOUTHWEST MONTANA. POST-FRONTAL SHOWERS WILL DEVELOP
THIS AFTERNOON AND CONTINUE INTO THURSDAY, YIELDING A 60 TO 80
PERCENT PROBABILITY OF WETTING RAIN (0.10 INCHES OR GREATER)
ACROSS THE MAJORITY OF WESTERN MONTANA AND NORTH CENTRAL IDAHO.
THE NOTABLE EXCEPTION TO THIS PRECIPITATION IS FAR SOUTHWEST MONTANA,
WHERE GUSTY WINDS AND LOW RELATIVE HUMIDITY WILL DRIVE CRITICAL
FIRE WEATHER CONDITIONS FROM THIS AFTERNOON THROUGH THURSDAY
AFTERNOON. ELEVATED FIRE WEATHER CONDITIONS WILL LINGER INTO
FRIDAY DUE TO THE SLOW FRONTAL PROGRESSION.
LOOKING AHEAD, PERSISTENT SOUTHWESTERLY FLOW ALOFT WILL DOMINATE
THURSDAY INTO FRIDAY AS A BROAD UPPER TROUGH SETTLES OVER THE
PACIFIC NORTHWEST. THIS PATTERN SUPPORTS NEAR TO SLIGHTLY BELOW
NORMAL TEMPERATURES ALONGSIDE DAILY SCATTERED AFTERNOON AND
EVENING CONVECTION. NORTH-CENTRAL IDAHO IS FAVORED FOR HEAVIER
ACCUMULATIONS DURING THIS TIMEFRAME, WITH HIGH PROBABILITIES (60
TO 80 PERCENT) OF EXCEEDING 0.50 INCHES.
ENSEMBLE GUIDANCE INDICATES GENERAL TROUGHING WILL PERSIST THROUGH
THE WEEKEND BEFORE A MORE PRONOUNCED SHORTWAVE EJECTS ACROSS THE
REGION ON MONDAY. APPROXIMATELY 50 PERCENT OF ENSEMBLE SOLUTIONS
DEPICT A CLOSED LOW TAPPING INTO DEEPER TROPICAL MOISTURE, WHICH
ALIGNS WITH CURRENT NBM PROBABILITIES OF 50 TO 70 PERCENT FOR
WIDESPREAD PRECIPITATION EXCEEDING 0.25 INCHES TO START THE NEXT
WORK WEEK ACROSS A LARGE SWATH OF THE NORTHERN ROCKIES.
AVIATION
AVIATION INTERESTS ACROSS WESTERN MONTANA AND NORTH
CENTRAL IDAHO WILL EXPERIENCE WIDESPREAD IMPACTS TODAY AS AN
UPPER-LEVEL DISTURBANCE AND COLD FRONT SWEEP THROUGH THE REGION.
SHOWERS AND THUNDERSTORMS INITIATING OVER NORTH-CENTRAL IDAHO THIS
MORNING WILL TRACK NORTHEASTWARD ACROSS THE CONTINENTAL DIVIDE BY
21Z-22Z (3-4 PM MDT), PRODUCING LOCALIZED MVFR TO IFR CONDITIONS
IN BRIEF HEAVY RAIN, MOUNTAIN OBSCURATIONS, AND ERRATIC OUTFLOW
WIND GUSTS OF 25 TO 45 KTS. RECENT HIGH-RESOLUTION GUIDANCE
HIGHLIGHTS A CORRIDOR FROM LEMHI COUNTY (KSMN) NORTHEASTWARD
THROUGH SILVER BOW COUNTY (KBTM) FOR STRONGER CONVECTIVE CELLS
CAPABLE OF HAIL AND NEAR-SEVERE GUSTS BETWEEN 19Z AND 21Z (1-3 PM
MDT). FOLLOWING THE FRONTAL PASSAGE, ELEVATED GRADIENT WINDS WILL
PERSIST ACROSS LEMHI COUNTY AND SOUTHWEST MONTANA UNTIL SUNSET,
WHILE WIDESPREAD POST FRONTAL SHOWERS FILL IN ACROSS THE BROADER
REGION AND CONTINUE INTO THURSDAY, MAINTAINING PERIODS OF REDUCED
FLIGHT CATEGORIES.
MSO WATCHES/WARNINGS/ADVISORIES
MT...RED FLAG WARNING UNTIL 8 PM MDT THURSDAY FOR EAST BEAVERHEAD.
ID...NONE.
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