A low pressure circulation moving through central Idaho brought a moist and unstable airmass to western Montana. Thunderstorms capable of producing hail and heavy rain in a short period of time were reported.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS MSO wrote it up.
A low pressure circulation moving through central Idaho brought a moist and unstable airmass to western Montana. Thunderstorms capable of producing hail and heavy rain in a short period of time were reported.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Missoula, MT wrote its last area forecast discussion before the first event at Aug 18, 1:44 PM MST, 46 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MISSOULA MT 244 PM MDT WED AUG 18 2010 .DISCUSSION...A FEW THUNDERSTORMS HAVE DEVELOPED THIS AFTERNOON ACROSS SOUTHWEST MONTANA AND CENTRAL IDAHO. EXPECT CONVECTION TO PERSIST IN THIS GENERAL REGION THROUGH THE EVENING HOURS. THE MAIN THREAT FROM THUNDERSTORMS TODAY WILL BE STRONG GUSTY WINDS AND SOME SMALL HAIL. THURSDAY AND FRIDAY A DRIER AIRMASS IS ANTICIPATED UNDER SLIGHTLY LOWERING HEIGHTS ALOFT. INCREASED WINDS WILL BE THE MAIN IMPACT DURING THIS TIME FRAME AS PRESSURE GRADIENTS ALOFT AND AT THE SURFACE WILL INCREASE. WIDESPREAD WIND GUSTS...FROM THE WEST/SOUTHWEST...EACH AFTERNOON AND EVENING ARE EXPECTED TO REACH 25-30 MPH IN MANY PLACES. THESE INCREASED WINDS WILL ALSO PRODUCE CHOPPY CONDITIONS ON FLATHEAD LAKE. ALSO EXPECTED IS A 5 DEGREE DROP IN TEMPS...WITH READINGS NEAR NORMAL FOR THIS TIME OF YEAR. ON SATURDAY...A LOW PRESSURE TROUGH WILL AMPLIFY OFF THE WEST COAST. AS A RESULT...HEIGHTS AND TEMPERATURES AND SOUTHWEST FLOW WILL INCREASE MODESTLY. EXPECT AN INCREASE IN MOISTURE OR CLOUDS AT THE MID LEVELS ON SATURDAY WITH A SLIGHT CHANCE OF CONVECTION LATE IN THE DAY IN SOUTHWEST MONTANA AND LEMHI COUNTY IN IDAHO. THUNDERSTORMS WILL BE POSSIBLE SUNDAY AFTERNOON AS THE TROUGH OF LOW PRESSURE MOVES ACROSS WESTERN MONTANA. A FEW SHOWERS OR THUNDERSTORMS WILL LINGER INTO NEXT WEEK BEFORE DRYING OUT ON WEDNESDAY. && .AVIATION...A LOW PRESSURE SYSTEM WILL SWING THROUGH CENTRAL IDAHO AND THEN INTO WESTERN MONTANA THIS AFTERNOON AND HELP TO INITIATE THUNDERSTORMS ACROSS THE REGION. THE BEST THUNDERSTORM DEVELOPMENT WILL BE OVER KBTM...KSMN...AND KMSO TERMINALS THROUGH LATER THIS EVENING. THUNDERSTORMS IN THESE LOCATIONS WILL HAVE THE CAPABILITY OF PRODUCING ERRATIC GUSTY WINDS. CONVECTIVE ACTIVITY IS EXPECTED TO DIMINISH BY MIDNIGHT. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...NONE. ID...NONE. && SHORT TERM...RPN LONG TERM....KOLATA AVIATION...ALLEGRETTO
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MISSOULA MT 324 PM MDT WED AUG 18 2010 MTZ004-182200- LOWER CLARK FORK REGION- 324 PM MDT WED AUG 18 2010 ...SIGNIFICANT WEATHER ADVISORY FOR EASTERN MINERAL COUNTY UNTIL 400 PM MDT... AT 318 PM MDT...STORM SPOTTERS REPORTED A STRONG THUNDERSTORM NEAR TARKIO...OR 17 MILES SOUTHEAST OF SUPERIOR...MOVING EAST AT 5 MPH. SMALL HAIL AND VERY HEAVY RAIN CAN BE EXPECTED WITH THIS STORM. PONDING OF WATER NEAR TARKIO IS POSSIBLE ON I-90. PRECAUTIONARY/PREPAREDNESS ACTIONS... IF THREATENING WEATHER APPROACHES YOUR AREA...GO INDOORS AND STAY AWAY FROM WINDOWS. IF YOU ARE CAUGHT OUTSIDE...MOVE TO A WELL PROTECTED AREA. && LAT...LON 4713 11470 4697 11457 4689 11472 4706 11482 TIME...MOT...LOC 2122Z 248DEG 3KT 4701 11464
The Missoula radar (KMSX), 38 km away, was scanning. The volume nearest the first event began at 21:28 UTC.
3 heavy rain, 1 hail. Local standard time, as filed.
Brief heavy rain was mixed with hail at Fish Creek and the Clark Fork River. Precipitation measured in at 0.40 inches in less than 30 minutes.
A spotter reported 0.30 inches of rain in 15 minutes.
A trained spotter reported 0.50 inches of rain in less than 30 minutes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2010Every state in 2010This day in weather historyWarnings in Montana, August 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 258064, 258065, 258063, 258067.