Thunderstorms developed from an unstable airmass during the evening hours over Broadwater County. Wind gusts in excess of 60 mph 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 TFX wrote it up.
Thunderstorms developed from an unstable airmass during the evening hours over Broadwater County. Wind gusts in excess of 60 mph 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 Great Falls, MT wrote its last area forecast discussion before the first event at Aug 14, 4:50 PM MST, 2 hours 10 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 550 PM MDT SUN AUG 14 2011 .DISCUSSION... TONIGHT THROUGH TUESDAY...AN UPPER LEVEL TROUGH ALONG THE BC/PAC NW COAST WILL CONTINUE TO PUSH INLAND TONIGHT AND TOMORROW...CROSSING THE NORTHERN ROCKIES AND MT MONDAY NIGHT. A WEAK MID LEVEL DISTURBANCE IN SW FLOW ALOFT AND UPPER LEVEL JET AHEAD OF THE TROUGH WILL LIFT NE INTO THE AREA TONIGHT AND EXPECT A FEW THUNDERSTORMS TO DEVELOP AND MOVE NE INTO THE AREA THIS EVENING. LOWER LEVELS WILL INITIALLY BE VERY WARM AND DRY THIS EVENING...PRODUCING FAVORABLE CONDITIONS FOR GUSTY WINDS WITH ANY CELLS THAT DEVELOP. LATER TONIGHT...MODELS DEPICT A SW TO NE CORRIDOR OF SHOWER ACTIVITY GENERALLY ALONG AND NORTH OF A LINE FROM HELENA TO GREAT FALLS TO HAVRE AND THIS IS REASONABLE GIVEN UPPER LEVEL JET DYNAMICS AND COOLING AT MID LEVELS MOVING INTO WESTERN MT AHEAD OF THE TROUGH. COOLING ALOFT WILL CONTINUE THROUGH MONDAY AND MONDAY NIGHT AS THE UPPER LEVEL TROUGH MOVES INTO THE NORTHERN ROCKIES WITH INSTABILITY AGAIN BRINGING THE CHANCE FOR AFTERNOON AND EVENING CONVECTION...THIS TIME MORE FOCUSED ACROSS SW AND EASTERN ZONES. HIGH PRESSURE BUILDS IN BEHIND THE TROUGH ON TUESDAY FOR DRY CONDITIONS. TEMPERATURES WILL BE CLOSER TO SEASONAL AVERAGES MONDAY AND ABOUT 5 DEGREES BELOW AVERAGE ON TUESDAY. HOENISCH TUESDAY NIGHT THROUGH SUNDAY NIGHT...MEDIUM RANGE MODELS SEEM TO HAVE COME INTO BETTER AGREEMENT TONIGHT WITH THE FORECAST SOLUTION DURING THIS PERIOD. A MODERATE WESTERLY FLOW ALOFT IN THE WAKE OF THE EXITING SHORTWAVE TROUGH WILL KEEP WINDS BREEZY AND WESTERLY AT THE SURFACE TUESDAY EVENING. WEAK DISTURBANCES IN THE FLOW WILL ALSO KEEP A SLIGHT CHANCE OF SHOWERS/THUNDERSTORMS ALONG THE ROCKY MOUNTAIN FRONT AND IN SOUTHWEST/CENTRAL MONTANA DURING THE EVENING. FOR THE REMAINDER OF THE PERIOD...THE AREA WILL BE BETWEEN A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE SOUTHWESTERN CONUS AND A BROAD UPPER LEVEL TROUGH OF LOW PRESSURE OVER SOUTHWEST CANADA. THE RESULTING WEST-NORTHWESTERLY FLOW ALOFT WILL GENERALLY BE DRY AND TEMPERATURES WILL MOSTLY BE NEAR NORMAL. HOWEVER...DISTURBANCES MOVING ACROSS NORTH CENTRAL/CENTRAL MONTANA THURSDAY NIGHT AND AGAIN FRIDAY AFTERNOON/NIGHT WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS. DISTURBANCES WILL ALSO MOVE ACROSS SOUTHWEST MONTANA BEGINNING FRIDAY AFTERNOON AND CONTINUING THROUGH THE WEEKEND FOR A SLIGHT CHANCE OF MOUNTAIN SHOWERS/THUNDERSTORMS MAINLY IN THE AFTERNOON/EVENING HOURS. WINDS WILL ALSO BECOME BREEZY AND WESTERLY AHEAD OF A WEAK CANADIAN COLD FRONT FRIDAY AFTERNOON AND EVENING...WHILE TEMPERATURES ONLY COOL SLIGHTLY BEHIND THE FRONT ON SATURDAY. COULSTON && .AVIATION... UPDATED 2350Z. VFR CONDITIONS EXPECTED ACROSS THE REGION NEXT 24 HRS. HIGH PRESSURE RIDGE CENTERED OVER ERN MT. WEAK DISTURBANCES AND ASSOCIATED MOISTURE MOVING ALONG WEST SIDE OF RIDGE WILL TO BRING INCREASING MID-LEVEL CLOUD COVER AND CHANCE OF ISOLATED SHOWERS AND THUNDERSTORMS GENERALLY 06Z TO 14Z. ANOTHER DISTURBANCE TO GENERATE MORE ISOLATED SHOWERS AND THUNDERSTORMS AFTER 20Z. && .FIRE WEATHER... ISOLATED THUNDERSTORMS ARE EXPECTED THIS EVENING WITH FAST STORM MOTION AND WARM/DRY LOWER LEVELS IN THE ATMOSPHERE CREATING FAVORABLE CONDITIONS FOR GUSTY DOWNDRAFT WINDS WITH PRECIPITATION AMOUNTS OF A TRACE TO FEW HUNDREDTHS OF AN INCH UNDER ANY CELLS THAT DEVELOP. MOISTURE DOES INCREASE SOME AFTER MIDNIGHT AND EXPECT SHOWERS TO BECOME MORE WIDESPREAD OVER WESTERN AND NORTHERN DISTRICTS LATER TONIGHT. SLIGHTLY COOLER BUT BREEZY TO WINDY CONDITIONS ARE EXPECTED MONDAY. HOENISCH && .PRELIMINARY POINT TEMPS/POPS... GTF 57 82 49 79 / 30 20 30 0 CTB 52 74 44 75 / 30 20 20 0 HLN 55 81 51 81 / 30 20 30 0 BZN 49 84 45 80 / 20 20 30 10 WEY 40 75 33 71 / 20 20 20 20 DLN 50 80 44 77 / 20 20 20 10 HVR 55 85 49 78 / 60 40 20 10 LWT 54 80 50 74 / 30 30 50 10 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREAT FALLS MT 419 AM MDT SUN AUG 14 2011 MTZ008>015-044>055-151030- BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL- CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON- TOOLE-LIBERTY-EASTERN PONDERA-BLAINE- SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS- JEFFERSON-BROADWATER-MEAGHER-GALLATIN- 419 AM MDT SUN AUG 14 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The Great Falls radar (KTFX), 129 km away, was scanning. The volume nearest the first event began at 01:59 UTC.
2 thunderstorm wind. Local standard time, as filed.
A thunderstorm produced a wind gust to 70 mph at Townsend 8W (the Elkhorn RAWS site).
A thunderstorm produced a wind gust to 64 mph at Townsend 7NNW (the Silos Recreation site).
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2011Every state in 2011This day in weather historyWarnings in Montana, August 2011
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: 333450, 333451.