A supercell thunderstorm developed over far southwestern Jackson County and northeastern Shannon County and moved southeastward. The storm produced hail as large as baseballs across portions of northeastern Shannon and Bennett Counties.
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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 UNR wrote it up.
A supercell thunderstorm developed over far southwestern Jackson County and northeastern Shannon County and moved southeastward. The storm produced hail as large as baseballs across portions of northeastern Shannon and Bennett Counties.
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 Rapid City, SD wrote its last area forecast discussion before the first event at Aug 18, 1:50 PM MST, 1 hour 45 minutes earlier.
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 250 PM MDT THU AUG 18 2011 .DISCUSSION...WATER VAPOR IMAGERY SHOWS NEAR ZONAL FLOW ACROSS THE REGION AS IT SITS BETWEEN RIDGING OVER THE SOUTHERN ROCKIES AND A TROUGH ACROSS CENTRAL CANADA. A SERIES OF EMBEDDED WAVES WERE CROSSING OVER THE AREA INTO WYOMING. SURFACE ANALYSIS SHOWS A COLD FRONT JUST CROSSING K2WX AND CONTINUING ITS SOUTHWARD PROGRESSION. A DRY LINE WAS ALSO OBSERVED STRETCHING NORTH TO SOUTH ACROSS THE EASTERN HALF OF THE BLACK HILLS. RADAR SHOWS ISOLATED STORMS DEVELOPING AHEAD OF THE FRONTAL BOUNDARY OVER THE NORTHERN BLACK HILLS AREA BETWEEN THE FRONTAL BOUNDARY AND DRY LINE WHERE LOW LEVEL CONVERGENCE IS INCREASING. STORMS WILL CONTINUE TO DEVELOP TONIGHT THOUGH SHOULD REMAIN ISOLATED IN COVERAGE. THE STORMS WILL REMAIN AHEAD OF THE FRONTAL BOUNDARY WHERE MLCAPE RANGES FROM 1000 J/KG IN WESTERN SOUTH DAKOTA TO 3000 J/KG ACROSS PARTS OF SOUTH CENTRAL SOUTH DAKOTA. STORMS WILL PUSH EASTWARD AS THE FRONT SLIDES ACROSS THE CWA THIS EVENING. SOME STORMS MAINLY ACROSS CENTRAL SOUTH DAKOTA COULD BECOME SEVERE. ALL CONVECTION IS EXPECTED TO EXIT THE CWA BY 06Z. MODELS SHOW THE FRONTAL BOUNDARY STALLING NEAR THE SOUTH DAKOTA/NEBRASKA BORDER EARLY FRIDAY MORNING AS THE SURFACE HIGH SHIFTS NORTHEAST OF THE AREA. EASTERLY FLOW WILL RETURN TO THE CWA IN THE AFTERNOON WITH WEAK THETA E ADVECTION DEVELOPING ONCE AGAIN. COULD SEE SOME STORMS DEVELOP IN THE AFTERNOON AND EVENING AS THE ATMOSPHERE DESTABILIZES. THE BEST CHANCES WILL BE ACROSS THE SOUTHERN HILLS IN THE EVENING WHERE THE BEST INSTABILITY WILL BE. TEMPERATURES WILL BE IN THE MID 70S TO MID 80S. SLIGHTLY WARMER TEMPERATURES ARE EXPECTED SATURDAY AS EASTERLY FLOW BECOMES MORE SOUTHERLY. SLIGHT CHANCES OF STORMS ARE AGAIN EXPECTED...BUT WITH WEAK SHEAR IN PLACE...SEVERE STORMS ARE NOT EXPECTED. EXTENDED...THE UNSETTLED WEATHER PATTERN WILL CONTINUE ON SUNDAY BEFORE AN UPPER LEVEL RIDGE BUILDS INTO THE NRN PLAINS EARLY NEXT WEEK...BRINGING MOSTLY DRY WEATHER ALONG WITH TEMPS ABOVE AVERAGE FOR MUCH OF NEXT WEEK. && .AVIATION...ISOLD/SCT TSTMS ARE POSSIBLE THIS AFTERNOON AND EVENING. LOCAL MVFR/IFR CONDS ARE POSSIBLE IN ANY TSTMS. OTHERWISE...VFR CONDS ARE EXPECTED THRU 06Z WITH SOME MVFR CIGS POSSIBLE AFTER O6Z ACROSS THE SD PLAINS. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RAPID CITY SD 648 AM MDT THU AUG 18 2011 SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058- 071-191300- BENNETT-BUTTE-CENTRAL BLACK HILLS-CUSTER CO PLAINS-FALL RIVER-HAAKON- HARDING-HERMOSA FOOT HILLS-JACKSON-MELLETTE-NORTHEASTERN CROOK- NORTHERN BLACK HILLS-NORTHERN CAMPBELL-NORTHERN FOOT HILLS- NORTHERN MEADE CO PLAINS-PENNINGTON CO PLAINS-PERKINS-RAPID CITY- SHANNON-SOUTHERN BLACK HILLS-SOUTHERN CAMPBELL-SOUTHERN FOOT HILLS- SOUTHERN MEADE CO PLAINS-STURGIS/PIEDMONT FOOT HILLS-TODD-TRIPP- WESTERN CROOK-WESTON-WYOMING BLACK HILLS-ZIEBACH- 648 AM MDT (748 AM CDT) THU AUG 18 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN SOUTH DAKOTA AND NORTHEASTERN WYOMING. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND TONIGHT ACROSS MUCH OF THE WESTERN AND SOUTH CENTRAL SOUTH DAKOTA PLAINS. THERE IS A SLIGHT RISK FOR SEVERE STORMS ACROSS SOUTH CENTRAL SOUTH DAKOTA THIS AFTERNOON AND EARLY EVENING...MAINLY NEAR AND EAST OF A LINE FROM PHILIP TO MARTIN. LARGE HAIL WILL BE THE PRIMARY THREAT FROM SEVERE STORMS...WITH STRONG WIND GUSTS AND AN ISOLATED TORNADO ALSO POSSIBLE. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THERE WILL BE A DAILY CHANCE FOR THUNDERSTORMS ACROSS MUCH OF THE AREA THROUGH SUNDAY. THERE IS A POTENTIAL FOR STRONG STORMS ACROSS PORTIONS OF NORTHEASTERN WYOMING AND SOUTHWESTERN SOUTH DAKOTA FRIDAY AFTERNOON AND EVENING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED TODAY.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RAPID CITY SD 346 PM MDT THU AUG 18 2011 SDZ013-073-182230- NORTHERN MEADE CO PLAINS SD-SOUTHERN MEADE CO PLAINS SD- 346 PM MDT THU AUG 18 2011 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN MEADE COUNTY UNTIL 430 PM MDT... AT 340 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING SEVERAL STRONG THUNDERSTORMS NEAR STONEVILLE...FAIRPOINT...RED OWL AND OPAL...GENERALLY MOVING EAST AT 15 MPH. HAIL UP TO THE SIZE OF PENNIES ARE EXPECTED WITH THESE STORMS. LOCATIONS NEAR THE PATH OF THESS STORMS INCLUDE... OPAL... MAURINE... MUD BUTTE... IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING. RUDGE
The Rapid City radar (KUDX), 86 km away, was scanning. The volume nearest the first event began at 22:36 UTC.
6 hail. Local standard time, as filed.
Most of the hail was golf ball size or smaller.
Large hail damaged buildings and vehicles in Martin.
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: 340845, 344895, 340846, 340850, 340847, 340849.