654
FXUS65 KMSO 250817
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
217 AM MDT THU JUN 25 2026
DISCUSSION
KEY MESSAGES:
- ANOTHER ROUND OF THUNDERSTORMS FOR WESTERN MONTANA TODAY.
- A COLD FRONT FRIDAY WILL BRING MORE STORMS, AND A BIG COOL DOWN
FOR THE WEEKEND.
- WET WEEKEND AND START TO EARLY NEXT WEEK.
- POTENTIAL FOR MOUNTAIN SNOW AND AN ALL AROUND HYPOTHERMIA RISK
IN THE MOUNTAINS THIS WEEKEND AND EARLY NEXT WEEK.
AN UPPER LEVEL SHORTWAVE OVER THE AREA IS SUPPORTING THUNDERSTORMS
AND SHOWERS ACROSS NORTHWEST MONTANA THIS MORNING. FOR MOST OF THE
MORNING, THESE STORMS SHOULD STAY AROUND LIBBY, KALISPELL, AND
AREAS NORTH OF THERE. BUT AS THE SUN COMES UP THIS MORNING AND
DESTABILIZES THE ATMOSPHERE, WE CAN EXPECT AN EARLY START TO
CONVECTION BY NOON ACROSS MUCH OF WESTERN MONTANA, ESPECIALLY
ALONG INTERSTATE-90 AND AREAS NORTH. STORMS ARE NOT EXPECTED TO BE
SEVERE, AND WILL MOSTLY PRODUCE HEAVY RAIN.
TOMORROW, A COLD FRONT WILL SWEEP ACROSS THE REGION CAUSING A
DRASTIC CHANGE IN THE WEATHER PATTERN. IT WILL START WITH
THUNDERSTORMS, BUT BEHIND THE FRONT THE SNOW LEVELS WILL FALL AND
WE CAN EXPECT TO SEE SOME SNOW FALLING BY SUNDAY MORNING IN THE
ANACONDA-PINTLAR, SAPPHIRE, AND BITTERROOT MOUNTAINS AS WELL AS
ALONG THE CONTINENTAL DIVIDE. THE UPPER LEVEL LOW AND COLD AIR
WILL MAINLY BE CENTERED SOUTH OF THE REGION, SO THE LOWEST SNOW
LEVELS ARE ACTUALLY EXPECTED SOUTH OF INTERSTATE-90. THIS SYSTEM
WILL MOVE SLOWLY, AND LAST THROUGH THE WEEKEND CAUSING A LOT OF
RAIN, WITH MANY LOCATIONS SOUTH OF A LINE FROM MISSOULA TO HELENA
HAVING A 70-90 PERCENT CHANCE OF PICKING UP 1 INCH OR MORE OF RAIN
BY SUNDAY MORNING. IN CENTRAL IDAHO, AREAS EAST OF GRANGEVILLE AND
SOUTH OF HIGHWAY-12 WILL BE THE HARDEST HIT, ESPECIALLY ALONG THE
SALMON RIVER CORRIDOR. ALL OF THESE AREAS SHOULD BE ON THE LOOKOUT
FOR RAPIDLY RISING SMALL STREAMS AND RIVERS. IF YOU'RE OUT
RECREATING ON ANY SMALL STREAMS AND RIVERS, BE PREPARED FOR
RAPIDLY CHANGING FLOWS AND MUCH COOLER TEMPERATURES.
IF YOU'LL BE OUT IN THE BACK COUNTRY IN THE MOUNTAINS, CONDITIONS
THIS WEEKEND WILL FAVOR HYPOTHERMIA IF YOU'RE UNABLE TO STAY DRY.
SUNDAY INTO MONDAY ESPECIALLY HAVE POTENTIAL WET, HEAVY SNOW ABOVE
6,000 FT.
BY MONDAY THE UPPER LEVEL LOW STARTS TO MOVE FASTER, BUT IS
FORECAST TO MOVE DIRECTLY OVER WESTERN MONTANA. THIS IS WHEN
NORTHWEST MONTANA WILL SEE THEIR HEAVIEST PRECIPITATION WITH THIS
SYSTEM. THOUGH GLACIER NATIONAL PARK WILL START TO SEE MORE
AUSTERE CONDITIONS BY SATURDAY, LATE SUNDAY INTO TUESDAY WILL BE
THE TOUGHEST CONDITIONS UP THERE.
AVIATION
ISOLATED THUNDERSTORMS WILL CONTINUE THIS MORNING
ACROSS NORTHWEST MONTANA, POTENTIALLY IMPACTING TERMINAL KGPI EVEN
IN THE EARLY MORNING HOURS. BY 25/18Z CONVECTION WILL INITIATE
ALONG INTERSTATE-90 AND AREAS NORTH AND EAST. A FEW ENSEMBLE
MEMBERS ALSO SHOW SOME ISOLATED CELLS IN CENTRAL IDAHO AFFECTING
GRANGEVILLE AFTER 25/20Z. THE MOST LIKELY TERMINALS TO BE AFFECTED
BY THUNDERSTORMS ARE KGPI AND KBTM, WITH KMSO BEING IN THE AREA
WHERE THEY FORM BUT ARE NOT YET MATURE. TERMINALS KSMN AND KHRF
ARE LESS LIKELY TO BE IMPACTED AS THE UPPER LEVEL FEATURE
SUPPORTING THE STORMS WILL HAVE MOVED FARTHER EAST. STORMS ARE
EXPECTED TO END EARLY, SOMETIME AROUND 26/00Z DUE TO THE UPPER
LEVEL SHORTWAVE MOVING OUT OF THE REGION TO THE EAST.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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