604
FXUS65 KMSO 170852
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
252 AM 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
HIGH CONFIDENCE EXISTS AMONG DETERMINISTIC AND ENSEMBLE GUIDANCE FOR A
HIGHLY AMPLIFIED UPPER-LEVEL RIDGE BUILDING ACROSS THE NORTHERN ROCKIES
TODAY AND FRIDAY. THIS SYNOPTIC SETUP WILL FACILITATE RAPID WARMING,
DRIVING AFTERNOON HIGH TEMPERATURES INTO THE MID-TO-UPPER 80S ACROSS
WESTERN MONTANA AND THE MID-90S WITHIN THE LOWER ELEVATIONS OF CENTRAL
IDAHO. HIGH RESOLUTION MODELS SHOW AN INCREASED POTENTIAL FOR SHOWERS TO
DEVELOP ACROSS WESTERN MONTANA THIS AFTERNOON, WITH A FEW THUNDERSTORMS
POSSIBLE ALONG THE CONTINENTAL DIVIDE IN NORTHWEST MONTANA.
BY LATE FRIDAY NIGHT, A SURGE OF ANOMALOUS MONSOONAL MOISTURE WILL ADVECT
NORTHWARD FROM THE GREAT BASIN, PHASING WITH A WEAK SHORTWAVE TROUGH. THIS
COMBINED MOISTURE AND FORCING WILL YIELD WIDESPREAD SHOWERS AND
THUNDERSTORMS, PRIMARILY IMPACTING LEMHI COUNTY AND SOUTHWEST MONTANA
THROUGH SATURDAY, WITH PRIMARY HAZARDS INCLUDING TORRENTIAL RAINFALL AND
GUSTY, ERRATIC OUTFLOW WINDS. UNCERTAINTY REMAINS REGARDING THE NORTHERN
EXTENT OF THIS CONVECTIVE ACTIVITY, WITH SOME GUIDANCE PROJECTING THE
PRECIPITATION SHIELD ADVANCING AS FAR NORTH AS MISSOULA. IN THE WAKE OF
THIS TROUGH, ENSEMBLE CLUSTERS INDICATE UPPER-LEVEL RIDGING WILL RAPIDLY
RE-ESTABLISH OVER THE REGION, INITIATING ANOTHER PERIOD OF ABOVE-NORMAL
TEMPERATURES.
AVIATION
PREDOMINANTLY VFR CONDITIONS WILL PREVAIL ACROSS WESTERN MONTANA
AND NORTH CENTRAL IDAHO TODAY AND 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 AFTER
17/2100Z. 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.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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