746
FXUS65 KMSO 250846
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
246 AM MDT MON MAY 25 2026
DISCUSSION
KEY MESSAGES:
- ONE MORE DAY OF ABOVE-NORMAL TEMPERATURES TODAY.
- THUNDERSTORMS RETURN TO THE NORTHERN ROCKIES TODAY AND TOMORROW.
- A COOL AND WET PATTERN ARRIVES TOMORROW, LOWERING TEMPERATURES
AND BRINGING WIDESPREAD RAIN THROUGH FRIDAY.
A BRIEF PERIOD OF WARM AND DRY WEATHER DRIVEN BY A HIGH-PRESSURE
SYSTEM OVERHEAD WILL LAST THROUGH THIS AFTERNOON. AFTERNOON
TEMPERATURES WILL RISE TO AROUND 15 DEGREES ABOVE THE SEASONAL
AVERAGE. HOWEVER, THE LATEST FORECAST MODELS SHOW THUNDERSTORMS
DEVELOPING EARLIER IN THE DAY AHEAD OF AN APPROACHING COLD FRONT.
AS A RESULT, MULTIPLE LOCATIONS ACROSS WESTERN MONTANA AND NORTH-
CENTRAL IDAHO WILL SEE THUNDERSTORMS DEVELOP AS EARLY AS 2:00 PM.
THESE SHOWERS AND THUNDERSTORMS WILL EXPAND INTO NORTHWEST MONTANA
BY THE EVENING HOURS. CURRENT HIGH-RESOLUTION MODELS INDICATE
THUNDERSTORMS WILL BEGIN IN LEMHI COUNTY AND THE SOUTHERN
BITTERROOT VALLEY BETWEEN 1:00 PM AND 2:00 PM, AND TRACK FROM
SOUTH TO NORTH INTO WEST-CENTRAL MONTANA BETWEEN 4:00 PM AND 6:00
PM. THIS STORM TRACK HISTORICALLY BRINGS STRONG, GUSTY WINDS TO
AREAS IN THE BITTERROOT AND MISSOULA VALLEYS. THERE IS A 30
PERCENT CHANCE THAT GUSTS WILL EXCEED 40 MPH, AND A 10 TO 15
PERCENT CHANCE THEY WILL REACH 50 MPH WITH THESE THUNDERSTORMS.
KEEP A PLAN IN MIND TO SEEK SHELTER IF YOU HAVE OUTDOOR RECREATION
PLANS THIS AFTERNOON BETWEEN 1:00 PM AND 5:00 PM FOR LOCATIONS
SOUTH OF INTERSTATE 90, AND FROM 5:00 PM TO SUNSET FOR LOCATIONS
NORTH OF INTERSTATE 90 IN WESTERN MONTANA. THESE THUNDERSTORMS ARE
EXPECTED TO REACH THE FLATHEAD LAKE AREA BETWEEN 5:00 PM AND 6:00
PM. IN ADDITION TO SUDDEN, STRONG WIND GUSTS, FREQUENT LIGHTNING
AND SMALL HAIL ARE EXPECTED.
THE LOW-PRESSURE STORM SYSTEM RESPONSIBLE FOR THE MOIST SOUTHWEST
WINDS TRIGGERING TODAY'S THUNDERSTORMS WILL MOVE FURTHER INLAND,
TRACKING OVER EASTERN OREGON AND SOUTHERN IDAHO ON TOMORROW. THIS
WILL BRING A SHARP DROP IN TEMPERATURES TOMORROW, DROPPING DAYTIME
HIGHS TO AROUND 5 DEGREES BELOW SEASONAL AVERAGES.
UNCERTAINTY REMAINS REGARDING EXACTLY HOW MUCH RAIN WILL FALL.
TOTAL AMOUNTS WILL DEPEND HEAVILY ON THE EXACT SPEED AND PATH OF
THE LOW-PRESSURE STORM SYSTEM. CURRENT GUIDANCE FAVORS WIDESPREAD
RAINFALL FOR WESTERN MONTANA AND NORTH-CENTRAL IDAHO, WITH THE
HIGHEST TOTALS LIKELY FOCUSED SOUTH OF INTERSTATE 90, WHERE 0.25
TO 0.75 INCHES OF RAIN COULD FALL BY THE END OF THE DAY WEDNESDAY.
THE HELLS CANYON AREA COULD SEE UP TO 1 INCH OF RAIN.
RAIN CHANCES REMAIN ELEVATED THROUGH FRIDAY, WITH DAILY SHOWERS
AND THUNDERSTORMS DEVELOPING ACROSS THE NORTHERN ROCKIES. LONG-
RANGE FORECAST MODELS AGREE THAT THIS SLOW-MOVING LOW-PRESSURE
SYSTEM WILL DRIFT NORTHEAST INTO EASTERN IDAHO AND SOUTHWEST
MONTANA BY FRIDAY. THIS WOULD BRING THE THREAT OF HEAVY RAINFALL
TO WESTERN MONTANA, WHICH COULD CREATE A LOCALIZED FLOODING THREAT
FOR ISOLATED AREAS. CONFIDENCE IS CURRENTLY LOW ON EXACTLY WHERE
THE HEAVIEST RAIN WILL DEVELOP, BUT THE CHANCE FOR AT LEAST 0.50
INCHES OF RAIN IS HIGHEST (50 TO 60 PERCENT) SOUTH OF INTERSTATE
90 IN WESTERN MONTANA AND ALONG HIGHWAY 12 IN NORTH-CENTRAL IDAHO.
STAY TUNED FOR FURTHER UPDATES.
AVIATION
A TROUGH APPROACHING THE U.S. WEST COAST WILL SET UP
SOUTHWESTERLY AND EVENTUALLY SOUTHERLY FLOW INTO THE NORTHERN
ROCKIES TODAY. THIS IS A TYPICAL PATTERN FOR THUNDERSTORMS IN THIS
REGION, AND THE WEATHER MODELS STRONGLY SUPPORT CONVECTION.
THUNDERSTORMS WILL START FORMING IN IDAHO NEAR TERMINAL KSMN
AROUND 25/20Z QUICKLY DEVELOP FURTHER NORTH NEAR TERMINALS KHRF
AND KMSO. STORMS ARE NOT EXPECTED TO REACH KGPI UNTIL LATER IN THE
EVENING. CONVECTION WILL SUPPORT WIND GUSTS 40-50 MPH IN GENERAL
TODAY, BUT STRONGER STORMS ARE EXPECTED TOMORROW.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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