587
FXUS65 KMSO 172003
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
203 PM MDT WED JUN 17 2026
DISCUSSION
KEY MESSAGES:
- A BRIEF COOLING TREND TODAY BEFORE AN AMPLIFIED UPPER RIDGE
DRIVES TEMPERATURES BACK ABOVE NORMAL.
- A SURGE OF MONSOONAL MOISTURE FRIDAY NIGHT INTO SATURDAY MAY
BRING THUNDERSTORMS CAPABLE OF HEAVY RAIN AND GUSTY WINDS TO
SOUTHWEST MONTANA AND LEMHI COUNTY.
FORECASTS ARE HIGHLY CONFIDENT THAT A STRONG RIDGE OF HIGH
PRESSURE WILL BUILD ACROSS THE NORTHERN ROCKIES ON FRIDAY. THIS
WEATHER PATTERN WILL BRING QUICK WARMING, PUSHING FRIDAY AFTERNOON
TEMPERATURES INTO THE MID-TO-UPPER 80S ACROSS WESTERN MONTANA AND
INTO THE MID-90S IN THE LOWER VALLEYS OF CENTRAL IDAHO. COMPUTER
MODELS SHOW A SLIGHT CHANCE FOR SCATTERED SHOWERS TO DEVELOP
ACROSS WESTERN MONTANA THIS AFTERNOON AND AGAIN THURSDAY
AFTERNOON, WITH A FEW THUNDERSTORMS POSSIBLE ALONG THE CONTINENTAL
DIVIDE IN NORTHWEST MONTANA.
BY LATE FRIDAY NIGHT, AN UNUSUALLY STRONG SURGE OF MONSOONAL
MOISTURE WILL MOVE NORTH FROM THE GREAT BASIN, COMBINING WITH A
WEAK UPPER-LEVEL SHORTWAVE. THIS COMBINED MOISTURE AND ENERGY WILL
BRING WIDESPREAD SHOWERS AND THUNDERSTORMS, PRIMARILY IMPACTING
LEMHI COUNTY AND SOUTHWEST MONTANA THROUGH SATURDAY. THE MAIN
IMPACTS FROM THESE STORMS WILL BE HEAVY RAIN AND SUDDEN, STRONG
WIND GUSTS. UNCERTAINTY REMAINS REGARDING HOW FAR NORTH THESE
STORMS WILL TRAVEL, THOUGH SOME MODELS SHOW THE RAIN AND STORMS
MOVING AS FAR NORTH AS MISSOULA. ONCE THIS SYSTEM CLEARS OUT, A
HIGH-PRESSURE RIDGE WILL QUICKLY REBUILD OVER THE REGION, STARTING
ANOTHER PERIOD OF HOT, DRY WEATHER.
AVIATION
PREDOMINANTLY VFR CONDITIONS WILL PREVAIL ACROSS WESTERN
MONTANA AND NORTH CENTRAL IDAHO THROUGH FRIDAY UNDER THE INFLUENCE
OF A BUILDING UPPER-LEVEL RIDGE. THE PRIMARY OPERATIONAL CONCERN
WILL BE ISOLATED TO SCATTERED SHOWER DEVELOPMENT ACROSS WESTERN
MONTANA, WITH A FEW THUNDERSTORMS POSSIBLE ALONG THE CONTINENTAL
DIVIDE IN NORTHWEST MONTANA NEAR GLACIER NATIONAL PARK THIS
AFTERNOON AND AGAIN THURSDAY AFTERNOON. THERE IS A 20 PERCENT
PROBABILITY THEY COULD DEVELOP FAR ENOUGH WEST TO IMPACT KGPI.
GUSTY ERRATIC WINDS AND PERHAPS SMALL HAIL WILL BE THE MAIN
THREATS. WHILE WIDESPREAD FLIGHT RESTRICTIONS ARE NOT ANTICIPATED,
TERMINAL SITES NEAR THE DIVIDE MAY EXPERIENCE BRIEF, LOCALIZED
MVFR CONDITIONS AND GUSTY, ERRATIC OUTFLOW WINDS FROM PASSING
CONVECTION. WINDS WILL ONCE AGAIN BE BREEZY FROM THE WEST OR
NORTHWEST AREA WIDE THIS AFTERNOON, WITH GUSTS UP TO 25 KTS,
DIMINISHING AROUND SUNSET. THERE MAY BE A FEW SHOWERS AROUND
NORTHWEST MONTANA ON THURSDAY MORNING, FOLLOWED BY TYPICAL
AFTERNOON MIX DOWN WIND GUSTS OF 15 TO 20 KTS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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