Thunderstorms produced heavy rainfall which resulted in flash flooding east of Platte on the late morning and early afternoon of August 5th.
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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 FSD wrote it up.
Thunderstorms produced heavy rainfall which resulted in flash flooding east of Platte on the late morning and early afternoon of August 5th.
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 Sioux Falls, SD wrote its last area forecast discussion before the first event at Aug 5, 8:45 AM CST, 2 hours earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 945 AM CDT FRI AUG 5 2011 .DISCUSSION... FOG FINALLY BURNING OFF WITH KFSD BEING ONE OF THE LAST LOCATIONS TO IMPROVE. THUNDERSTORM DEVELOPMENT IN SOUTH CENTRAL SHOULD DIMINISH AND STORMS SHOULD DIURNALLY FALL APART. GRIDS REFLECT THE CURRENT SITUATION AND EXPECTED DISSIPATION. MOST OF THE CONVECTION SHOULD STAY TO THE SOUTH OF CWA AS SHORT WAVE PASSES THROUGH EASTERN NEBRASKA TODAY. BIGGEST QUESTION IS WHAT THE TEMPS WILL DO WITH THE MORNING CLOUDS AND FOG. ATTM...I WON'T BE TOUCHING THE HIGHS TOO MUCH IN THE GRIDS AS TEMPS ARE EXPECTED TO REBOUND QUICKLY. IT WILL FEEL A LITTLE MORE HUMID TODAY WITH THE HIGHER DEW POINT AIR. && .AVIATION... AS CIGS AND VSBYS IMPROVE FROM MORNING FOG...REMAINDER OF THE TAF TIME PERIOD SHOULD BE UNEVENTFUL EXCEPT FOR A FEW ISOLATED -SHRA AROUND MISSOURI RIVER. WILL NEED TO WATCH KSUX TAF TO SEE IF AN UPDATE WILL BE NECESSARY WITH POSSIBLE DEVELOPMENT. VFR WEATHER IS EXPECTED THROUGHOUT THE REMAINDER OF THE PERIOD. MAY INTRODUCE A FEW -SHRA/-TSRA IN KHON TAF LATE IN THE PERIOD OF 18Z TAF ISSUANCE BUT WILL TAKE A CLOSER LOOK BEFORE ISSUANCE. MAY NOT BE THAT SIGNIFICANT CHANCE TO MENTION. && .PREV DISCUSSION... ANOTHER SHORTWAVE TRACKING THROUGH NEBRASKA IS TRIGGERING CONVECTION OVER THE CENTRAL PORTIONS OF THAT STATE VERY EARLY THIS MORNING...AND LIKE YESTERDAY CANNOT RULE OUT THE POSSIBILITY OF SOME OF THIS ACTIVITY SCRAPING OUR FAR SOUTH TODAY AS THE FEATURE PUSHES EASTWARD INTO IOWA BY AFTERNOON. EVEN SO...WOULD LOOK LIKE ONLY A SLIGHT CHANCE OF POPS WITH BEST INSTABILITY AND FORCING REMAINING TO THE SOUTH OF OUR AREA. HIGH TEMPERATURES AGAIN LOOKING TO BE IN THE 80S...WITH COOLEST TEMPERATURES IN THE SOUTHEAST WHERE CLOUD COVER WILL BE MOST ABUNDANT THROUGH THE DAY. THETA E ADVECTION AND INSTABILITY REALLY CRANK UP TONIGHT OVER WESTERN AND CENTRAL SOUTH DAKOTA WITH THE DEVELOPMENT OF A 30 TO 40 KT LOW LEVEL JET OVER THAT AREA...AND MAY SEE SOME OF THIS ACTIVITY CREEP INTO OUR WESTERN ZONES LATE TONIGHT. WHILE COULD SEE AN ISOLATED SEVERE STORM IN OUR FAR WEST...GENERALLY THINK ANY STORMS THAT TRACK INTO OUR CWA WILL BE BELOW SEVERE LIMITS WITH WANING INSTABILITY AND EFFECTIVE SHEAR IN PLACE OVER EASTERN SOUTH DAKOTA. LOWS WILL BE IN THE MID AND UPPER 60S. A BETTER CHANCE OF THUNDERSTORMS WILL COME ON SATURDAY INTO SATURDAY EVENING AS A STRONG SHORTWAVE TRACKS ACROSS NORTH DAKOTA...PULLING A SURFACE COLD FRONT ACROSS OUR AREA DURING THIS TIME FRAME. THE BETTER CHANCES OF THUNDERSTORMS WILL REMAIN NORTH OF INTERSTATE 90...CLOSER TO BETTER FORCING TO OUR NORTH. INCREASING CAPE/EFFECTIVE SHEAR/LAPSE RATES WILL CONTRIBUTE TO AN ENHANCED CHANCE OF SEVERE STORMS OUT AHEAD OF THE FRONT ON SATURDAY AFTERNOON...AS TEMPERATURES CLIMB INTO THE MID AND UPPER 80S. COOLER AND DRIER CONDITIONS EXPECTED FOR SUNDAY AS HIGH PRESSURE BUILDS INTO THE REGION. HIGHS WILL RANGE FROM THE UPPER 70S IN OUR NORTHEASTERN ZONES TO MID 80S OVER SOUTH CENTRAL SOUTH DAKOTA. PRECIPITATION CHANCES THEN INCREASE AGAIN ON SUNDAY NIGHT AND MONDAY IN A RETURNING SOUTHERLY FLOW ON THE BACKSIDE OF THE HIGH AND ANOTHER COLD FRONT SWINGING THROUGH THE REGION ON MONDAY NIGHT. THIS WILL REINFORCE COOLER AIR ACROSS THE AREA...WITH HIGHS IN THE 70S TO LOWER 80S FOR TUESDAY AND WEDNESDAY...WITH LOWS IN THE 50S TO LOWER 60S. /JM && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 1026 AM CDT FRI AUG 05 2011 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-061200- AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA- CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE- DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON- IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN- LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN- OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN- SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON- 1026 AM CDT FRI AUG 05 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... WIDELY SCATTERED THUNDERSTORMS WILL BE POSSIBLE TODAY IN AREAS ALONG THE MISSOURI RIVER INTO PORTIONS OF NORTHWEST IOWA. THESE STORMS ARE NOT EXPECTED TO BE SEVERE. A FEW MORE THUNDERSTORMS MAY DEVELOP TONIGHT OVER CENTRAL SOUTH DAKOTA AND PUSH INTO THE JAMES RIVER VALLEY LATE. THESE STORMS ARE ALSO NOT EXPECTED TO BE SEVERE. FLOODING... MODERATE TO MAJOR FLOODING IS EXPECTED TO CONTINUE ON THE JAMES RIVER UNTIL FURTHER NOTICE. HIGH RELEASES ALONG THE MISSOURI RIVER WILL CONTINUE INTO LATE SUMMER. HIGH WATER LEVELS WILL CAUSE SIGNIFICANT IMPACTS BETWEEN CHAMBERLAIN AND SIOUX CITY. THE HIGH FLOWS ON THE MISSOURI RIVER WILL ALSO CAUSE FLOODING ON THE BIG SIOUX RIVER NEAR SIOUX CITY. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY SCATTERED THUNDERSTORMS MAY DEVELOP ACROSS THE AREA ON SATURDAY AS A COLD FRONT PUSHES THROUGH THE REGION. A FEW OF THESE STORMS COULD BE SEVERE WITH LARGE HAIL AND DAMAGING WIND. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK.
The Sioux Falls radar (KFSD), 158 km away, was scanning. The volume nearest the first event began at 16:46 UTC.
1 flash flood. Local standard time, as filed.
Heavy rainfall of about 4 inches caused flooding of several rural roads.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2011Every state in 2011This day in weather historyWarnings in South Dakota, 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: 339591.