463
FXUS65 KMSO 011741
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1141 AM MDT WED JUL 1 2026
DISCUSSION
KEY MESSAGES:
- SLOW MOVING THUNDERSTORMS WITH HEAVY RAIN WILL CAUSE A FLASH
FLOOD THREAT THROUGH THIS EVENING, ESPECIALLY IN THE SAPPHIRE
MOUNTAINS AND SOUTHWEST MONTANA.
- THUNDERSTORMS WILL BE A NEAR DAILY OCCURRENCE FOR LEMHI COUNTY,
ID AND SOUTHWEST MONTANA.
- GRADUAL WARMING AND DRYING TREND THROUGH THE WEEKEND.
A TROUGH OVER THE REGION TODAY COMBINED WITH ALL THE RECENT
MOISTURE IS A GOOD SET UP FOR THUNDERSTORMS. A LACK OF STRONG WIND
SHEAR OR REALLY ANY STRONG WINDS ALOFT AT ALL MEANS STORMS WILL
MOVE SLOWLY AT 12-20 MPH TOWARDS THE NORTHEAST. THIS SLOWER MOTION
AND AMPLE MOISTURE SUPPLY MEANS THE BIGGEST THREAT FROM THESE
STORMS WILL BE HEAVY RAIN. THE HREF SHOWS THE POTENTIAL FOR UP TO
0.80 INCHES OF RAIN IN UNDER AN HOUR THIS AFTERNOON. RAIN AMOUNTS
THIS HIGH WOULD ONLY OCCUR IN LIMITED AREAS DIRECTLY UNDER THE
CORE OF THE STRONGEST STORMS, AND WOULD NOT BE A WIDESPREAD EVENT.
STILL, THIS IS A CONCERN FOR POTENTIAL FLASH FLOODING, ESPECIALLY
CONSIDERING HOW MOIST THE SOILS ARE WITH THE RECENT RAIN. CURRENT
FORECASTS HAVE THESE STRONGER STORMS FOCUSED IN THE BITTERROOT
VALLEY AND AREAS EASTWARD AND SOUTH OF HIGHWAY 12, INCLUDING THE
SAPPHIRE MOUNTAINS.
THE TROUGH PATTERN WITH SOUTHWEST FLOW INTO THE REGION WILL
CONTINUE INTO EARLY NEXT WEEK, AND AS A RESULT, THUNDERSTORMS
REMAIN IN THE FORECAST THROUGH NEXT WEEK. THE AFFECTED REGION WILL
REMAIN FAIRLY CONSISTENT AS WELL WITH A FOCUS IN THE BITTERROOT
AND EASTWARD SOUTH OF HIGHWAY 12. THE FLASH FLOOD RISK IS EXPECTED
TO DIMINISH EACH DAY AS A LITTLE MORE MOISTURE GETS WORKED OUT OF
THE SYSTEM.
EVEN WITH THE TROUGH OVER THE REGION FOR THE NEXT WEEK, WE EXPECT
A GRADUAL WARMING AND DRYING TREND. THAT IS BECAUSE THE TROUGH
WILL TREND WEAKER WITH TIME. BY THIS WEEKEND MUCH OF THE REGION
WILL SEE RELATIVE HUMIDITY DROP INTO THE LOW 20 PERCENT RANGE WITH
THE SOUTHWESTERN PORTIONS OF IDAHO COUNTY, ID DROPPING INTO THE
TEENS AGAIN.
AVIATION
A BROAD TROUGH OVER THE REGION COMBINED WITH A VERY
MOIST AIR MASS IS ALREADY CAUSING CONVECTION THIS AFTERNOON.
TERMINAL KMSO WILL BE ON THE NORTHWESTERN EDGE OF THE CONVECTION,
WITH KGPI THE LEAST LIKELY TO BE AFFECTED BY STORMS. TERMINALS
KHRF, KSMN, AND KBTM ARE UNDER THREAT OF THUNDERSTORMS THROUGH
02/06Z WITH HEAVY RAIN AND SMALL HAIL AS THE MAIN THREATS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH THROUGH THIS EVENING FOR BITTERROOT/SAPPHIRE
MOUNTAINS...BUTTE/BLACKFOOT REGION...MISSOULA/BITTERROOT
VALLEYS.
ID...NONE.
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