687
FXUS65 KMSO 131949
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
149 PM MDT THU AUG 13 2026
DISCUSSION
KEY MESSAGES:
- ROUNDS OF SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY RAIN,
DEBRIS FLOW POTENTIAL ALONG WITH GUSTY WINDS (MAINLY WESTERN
MONTANA) THROUGH FRIDAY.
- TEMPORARY RELIEF FROM SMOKE WITH EASTERLY WINDS.
- GRADUAL WARMING AND DRYING TREND THIS WEEKEND, DAILY
THUNDERSTORM THREAT CONTINUES.
SHORT-TERM CONVECTION & HAZARDS:
SEVERAL ROUNDS OF SHOWERS/THUNDERSTORMS ARE EXPECTED THIS
AFTERNOON/EVENING AS A MONSOONAL MOISTURE SURGE INTERACTS WITH AN
APPROACHING PACIFIC TROUGH AND DAYTIME HEATING. PRIMARY HAZARDS
INCLUDE FREQUENT LIGHTNING, LOCALIZED HEAVY RAINFALL, AND GUSTY
OUTFLOW WIND GUSTS TO 40 MPH. THE LOCALIZED FLASH FLOOD THREAT IS
GREATEST ACROSS BURN SCARS, STEEP CANYONS, AND URBAN OR POORLY
DRAINED AREAS. HIGH RESOLUTION GUIDANCE POINTS TOWARD SOUTHWEST
MONTANA WITH THE HIGHEST PROBABILITY FOR STRONGER
THUNDERSTORM/HEAVIER RAIN RATES. FLOOD PRONE AREAS OF NORTHERN
LEMHI COUNTY AND BURN SCARS IN THE SOUTHERN BITTERROOT VALLEY ARE
ALSO A CONCERN. AFTER ANOTHER ROUND OF EARLY MORNING
SHOWERS/STORMS, A SIMILAR LOCALLY HEAVY RAIN AND DEBRIS FLOW
THREAT WILL EXIST ON FRIDAY AFTERNOON AND EVENING, WITH THE THREAT
AREA LIKELY SHIFTING SLIGHTLY FURTHER NORTH INTO WEST-CENTRAL
MONTANA.
TEMPERATURES & WIND IMPACTS:
COOLER AIR BEHIND THE TROUGH WILL TREND FRIDAY HIGH TEMPERATURES
5 TO 10 DEGREES BELOW SEASONAL NORMALS, WITH HIGHS PEAKING IN THE
MID-70S TO LOW 80S. WHILE EAST TO NORTHEAST WINDS WILL BE WEAKER
THAN YESTERDAY EVENING, ELEVATED BREEZES WILL CONTINUE TO PRODUCE
CHOPPY WATERS ON REGIONAL LAKES; RECREATIONAL BOATERS SHOULD
EXERCISE CAUTION.
EXTENDED PATTERN & SMOKE:
AN UPPER-LEVEL RIDGE WILL REBUILD OVER THE NORTHERN ROCKIES THIS
WEEKEND INTO EARLY NEXT WEEK. PERSISTENT SOUTHWESTERLY FLOW ALOFT
WILL MAINTAIN MONSOONAL MOISTURE TRANSPORT INTO THE REGION,
KEEPING PRECIPITABLE WATER LEVELS ELEVATED. THIS PATTERN WILL
SUSTAIN DAILY CHANCES FOR AFTERNOON SHOWERS AND THUNDERSTORMS
THROUGH NEXT WEEK, PREVENTING A FULL RETURN TO DRY CONDITIONS.
WILDFIRE SMOKE WILL REMAIN AN ONGOING CHALLENGE, WITH AIR QUALITY
EXPECTED TO DEGRADE SLOWLY THIS WEEKEND AS SOUTHWESTERLY FLOW
TRANSPORTS SMOKE PLUMES FROM SOURCE FIRES IN EASTERN WASHINGTON
AND OREGON.
AVIATION
SHOWER AND THUNDERSTORM COVERAGE WILL INCREASE THROUGH
THE DAY TODAY WITH CHANCES LASTING INTO THE OVERNIGHT AND EARLY
MORNING HOURS. LIGHTNING, LOW CEILINGS TO NEAR 5000 FT AGL,
BRIEF REDUCTIONS IN VISIBILITY, AND OUTFLOW WIND GUSTS OF UP TO
35 KNOTS ARE POSSIBLE NEAR STRONGER THUNDERSTORMS. NORTHERLY AND
EASTERLY DRAINAGE WINDS WILL DEVELOP THROUGH THE OVERNIGHT PERIOD.
THERE IS A LOW CHANCE FOR FOG AND LOW STRATUS DEVELOPMENT
OVERNIGHT THROUGH SUNRISE. WILDFIRE SMOKE WILL BEGIN TO BE
TRANSPORTED ALOFT OUT OF THE SOUTH AND WEST THROUGH THE WEEKEND
AND IS NOT ANTICIPATED TO SIGNIFICANTLY IMPACT VISIBILITY AT THIS
TIME.
MSO WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR BUTTE/BLACKFOOT
REGION.
ID...
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