061
FXUS65 KMSO 011732
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1132 AM MDT TUE SEP 1 2026
DISCUSSION
KEY MESSAGES:
- WIDESPREAD SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND
EVENING, WITH GUSTY OUTFLOW WINDS OF 30-50 MPH, BRIEF MODERATE
RAINFALL, AND LIGHTNING, STRONGEST STORMS SOUTH OF HIGHWAY 200.
- ANOTHER ROUND OF STORMS WEDNESDAY CAPABLE OF 30-50 MPH OUTFLOWS
AND HEAVY RAIN RATES UP TO 0.5 INCHES PER HOUR.
- PERSISTENT ACTIVE PATTERN LATE WEEK INTO THE WEEKEND UNDER
SOUTHWESTERLY FLOW, WITH A 20 PERCENT CHANCE OF A TROPICAL
MOISTURE TAP ON SUNDAY OR MONDAY.
AS LOW PRESSURE OFF THE PACIFIC NORTHWEST COAST BEGINS TO SHIFT
INLAND, A MOIST SOUTHWEST FLOW ALOFT WILL TRANSPORT MONSOON
MOISTURE FROM THE DESERT SOUTHWEST INTO NORTH CENTRAL IDAHO AND
WESTERN MONTANA. SHOWERS AND THUNDERSTORMS WILL DEVELOP THROUGH
NORTH CENTRAL IDAHO AND SOUTHWEST MONTANA BETWEEN 1 AND 3PM MDT
AND SHIFT NORTHWARDS INTO THE REST OF WESTERN MONTANA THROUGH 10
PM MDT TONIGHT. WITH THUNDERSTORMS MOVING INTO THE HOT AND DRY
AIRMASS ALREADY IN PLACE, GUSTY OUTFLOW WINDS WILL BE THE MAIN
THREAT. HIGH RESOLUTION MODELS GENERALLY SHOW GUST POTENTIAL
BETWEEN 30 TO 50 MPH WITH STORMS.
BY WEDNESDAY, AS THE LOW PRESSURE SYSTEM CONTINUES TO MOVE
EASTWARDS, A COLD FRONT WILL MOVE THROUGH THE REGION, FIRST
THROUGH NORTH CENTRAL IDAHO IN THE MORNING, THEN INTO WESTERN
MONTANA LATE MORNING THROUGH EARLY AFTERNOON. ANOTHER ROUND OF
THUNDERSTORMS IS EXPECTED TO DEVELOP AHEAD OF AND WITH THE COLD
FRONT. STORMS WILL BE MORE MOIST ON WEDNESDAY, WITH STRONGER
STORMS CAPABLE OF HALF AN INCH OF RAINFALL IN AN HOUR OR LESS.
WITH STRONG FORCING ALOFT, WEDNESDAY'S SET UP IS SLIGHT BETTER TO
FAVOR STRONG TO LOCALLY SEVERE THUNDERSTORMS IN THE AFTERNOON,
ESPECIALLY IN NORTHWEST MONTANA NEAR THE CONTINENTAL DIVIDE WHERE
A LATER FRONTAL PASSAGE WILL CORRESPOND WITH MAX DAYTIME HEATING.
HIGH RESOLUTION MODELS SHOW LOCALIZED GUSTS UP TO 60 MPH WILL BE
POSSIBLE. IT DOES APPEAR THE THREAT FOR STRONG STORMS WILL END
EARLIER IN THE DAY, POSSIBLY AS EARLY AS 6PM. THE GOOD NEWS: THERE
IS HIGH CONFIDENCE (80 PERCENT) OF WIDESPREAD WETTING RAIN (0.10
INCH OR GREATER) THROUGH THURSDAY MORNING OTHER THAN FOR FAR
SOUTHWEST MONTANA.
ACROSS FAR SOUTHWEST MONTANA GUSTY WINDS AND LOW AFTERNOON
RELATIVE HUMIDITY WEDNESDAY AFTERNOON AND EVENING ARE EXPECTED TO
CREATE CRITICAL FIRE WEATHER CONDITIONS THROUGH WEDNESDAY
AFTERNOON THROUGH THURSDAY AFTERNOON, BEFORE THE COLD FRONT
FINALLY PASSES THROUGH THURSDAY NIGHT.
SOUTHWESTERLY FLOW ALOFT WILL PERSIST THURSDAY INTO FRIDAY AS A
BROAD UPPER-LEVEL TROUGH SETTLES OVER THE PACIFIC NORTHWEST. THIS
PATTERN WILL KEEP TEMPERATURES NEAR TO SLIGHTLY BELOW LATE-SUMMER
AVERAGES ALONGSIDE PERIODIC SHOWERS AND THUNDERSTORMS,
PARTICULARLY DURING PEAK AFTERNOON AND EVENING HEATING. GUIDANCE
REMAINS IN SOLID AGREEMENT THAT TROUGHING WILL LINGER OVER THE
REGION THROUGH THE WEEKEND, WITH ROUGHLY 20 PERCENT OF ENSEMBLE
MEMBERS INDICATING A POTENTIAL TAP OF SIGNIFICANT TROPICAL
MOISTURE SUNDAY OR MONDAY. REGARDLESS OF WHETHER THIS TROPICAL
PLUME MATERIALIZES, THE NORTHERN ROCKIES WILL REMAIN EMBEDDED IN
AN ACTIVE, UNSETTLED WEATHER PATTERN THROUGH THE WEEKEND.
AVIATION
THUNDERSTORMS CAPABLE OF STRONG OUTFLOW WINDS
(25-45KTS) ARE THE PRIMARY WEATHER CONCERN THROUGH THIS EVENING.
CONVECTIVE INITIATION REMAINS ON TRACK ACROSS CENTRAL IDAHO BY
EARLY THIS AFTERNOON, WITH STORMS TRACKING NORTHEAST INTO WESTERN
MONTANA THROUGH MID-EVENING. PRIMARY OPERATIONAL HAZARDS INCLUDE
FREQUENT LIGHTNING AND ERRATIC OUTFLOW WINDS OF 25-45 KT. ALTHOUGH
CONVECTIVE INSTABILITY DIMINISHES NORTHWARD TOWARD THE I-90
CORRIDOR, LINEAR STORM ORGANIZATION WILL LIKELY SUSTAIN STRONG
OUTFLOW BOUNDARIES PUSHING INTO I-90 TERMINALS AND POTENTIALLY
INTO PORTIONS OF NORTHWEST MONTANA. SHOWERS AND ISOLATED
THUNDERSTORMS MAY LINGER THROUGH LATE EVENING.
BY 15Z WEDNESDAY, HIGH-RESOLUTION GUIDANCE INDICATES A SECONDARY
WAVE OF CONVECTION INITIATING ACROSS SOUTHWEST IDAHO AND LIFTING
NORTHEAST ACROSS THE NORTHERN ROCKIES THROUGH MID AFTERNOON.
OUTFLOW WINDS OF 30-45 KT WILL ONCE AGAIN SERVE AS THE PRIMARY
AVIATION HAZARD.
MSO WATCHES/WARNINGS/ADVISORIES
MT...RED FLAG WARNING FROM NOON WEDNESDAY TO 8 PM MDT THURSDAY FOR
EAST BEAVERHEAD.
ID...NONE.
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