Overview
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Two destructive supercell thunderstorms affected western South Dakota August 11, 2026. One storm produced giant hail (up to 4") and another produced extreme wind (up to 111 mph). Prolific Hail Producer (started in the Black Hills)This long-track thunderstorm, and prolific and destructive hail producer, formed just after 1:00 PM MDT in the northern Black Hills. The storm initially sat over this area, shedding updrafts off its northern flank and struggling to move off the hills. It then matured into a supercell and started moving southeast, producing numerous reports of quarter (1.0” diameter) to tennis ball size (2.50” diameter) hail from near Nemo, to near Johnson Siding, to near Rockerville. Hail covered the ground and resulted in numerous broken windshields in the Rockerville area. The storm continued southeast experiencing several mergers, impacting the Hayward to Hermosa corridor with numerous reports of baseball (2.75” diameter) and larger sized hail, with the largest received measurement coming in at 3.6” diameter 2 miles south-southwest of Hermosa measured by a storm chaser. The hail fell for 10-15 minutes in some areas! Shattered home and vehicle windows, dented vehicles, broken downspouts and gutters, and a destroyed carport were reported in this corridor. In far southeastern Custer County, a reliable storm spotter reported a short-lived, long rope funnel from the storm. As the storm tracked through Oglala Lakota County, a swath of baseball (2.75” diameter) to 4.00” diameter hail was reported across the Oglala and Pine Ridge areas, causing widespread and catastrophic damage to homes, vehicles, and gardens/vegetation. Numerous home and vehicle windows were smashed out, and roofs were damaged. A school district in Oglala was forced to delay the start of their school year due to significant damage to their fleet of school buses. This storm exited South Dakota just before 7:00 PM MDT and would go on to produce more 3.5” hail through north-central Nebraska. Extreme Wind Producer (started in southeast Montana)This destructive, long-track thunderstorm formed in far southeastern Montana, quickly becoming severe before moving into Harding County just after 4:00 PM MDT. The storm evolved into a high-impact, high-precipitation (HP) supercell for the first part of its lifespan tracking southeast across western South Dakota, producing damaging hail as large as baseballs (2.75” diameter) and knocking down power poles between Camp Crook and Harding, and then intensifying and producing destructive winds ranging from 61 MPH to 111 MPH (13 miles northeast of Newell) across Butte County. Tree and structural damage was reported near Castle Rock. As the storm reached Meade County, the supercell structure deteriorated as more convection formed on its northeastern flank and the system started to elongate into more of a linear mode. It produced wind gusts to 79 MPH 3 miles northwest of Wasta, 84 MPH 2 miles east of Cottonwood, and 102 MPH 4 miles east of Cactus Flat as it reached the Interstate 90 corridor in Pennington and Jackson counties. Half-dollar size hail (1.25” diameter) was also reported near Cedar Pass. Finally, the storm fully expanded/transitioned into a line as it continued to track southeast across Jackson, Mellette, Todd, and Tripp counties, producing widespread wind damage. Wind gusts reached 83 MPH 4 miles west-northwest of Cedar Butte, 96 MPH 1 mile south of White River, 90 MPH 7 miles east-southeast of Rosebud, and 83 MPH in Wewela. Damage in Cedar Butte, White River, Mission, Rosebud, and Okreek included structural damage, outbuildings blown over, numerous trees down, and windows blown out of homes and vehicles. The fairgrounds cook shack building in Rosebud collapsed, and the Tokala Inajinyo Youth Leadership Mentoring Program Resource Center 6 miles north-northeast of Rosebud was destroyed. 78 power poles were also reported down or damaged across Mellette County. The storm exited into Nebraska by 1:00 AM CDT, and continued to produce 60+ MPH wind gusts through northeast and eastern Nebraska. |
 Hail damage to building roof in Hayward, SD. Image courtesy Jan Gamble.  White River, SD. Image courtesy Zach Nelson.
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Photos
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| Hail Covering Highway 16 Courtesy Julie Carlson |
Oglala, SD Courtesy Cynthia New Holy |
2.5 miles west of Hermosa, SD Courtesy John Gregory |
7 miles west of Hermosa, SD Courtesy Carmella Helfrich |
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| Mission, SD Courtesy Gwen Foote |
Courtesy Casey Emery Krogman | White River, SD Courtesy Colleen Day |
White River, SD Courtesy Colleen Day |
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| Harding County, SD Courtesy Mike Smith |
Courtesy DeeAnn Deon | 5 miles southeast of Oglala, SD Courtesy Shanna Red |
Oglala, SD, Loneman Housing Courtesy Sheryl Starr |
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| Pine Ridge, SD Courtesy Dan Fitts |
3 miles southwest of Hermosa, SD Courtesy Dan Fitts |
North of Oglala, SD Courtesy Ryan Larmeu |
4 miles west of Hermosa, SD Courtesy Justin King |
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| Harding County, SD Courtesy Mike Smith |
Courtesy Lillian Wetsch Anderson | Hard Ranch Road, SD Courtesy Julie Milligan |
Pine Ridge, SD Courtesy Darien Hudspeth |
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| Pine Ridge, SD Courtesy Jennifer Clifford |
Pine Ridge, SD Courtesy Jancy Biggz |
Bear Country, SD Courtesy Shannon Powell |
Harding County, SD Courtesy Mike Smith |
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| Rockerville, SD Courtesy NWS Employee |
Rockerville, SD Courtesy NWS Employee |
Rockerville, SD Courtesy NWS Employee |
Rockerville, SD Courtesy NWS Employee |
Radar
Prolific Hail Producer (started in the Black Hills)
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| August 11, 2026, 305 PM MDT KUDX 8.0 Base Reflectivity Radar Image. Notice the ~35mi long TBSS | August 11, 2026, 548 PM MDT KUDX 0.5 Base Reflectivity Radar Image (about the same time as the 4" hail report) | August 11, 2026, 548 PM MDT KUDX 0.5 Base Reflectivity Radar Image (just before it impacts Pine Ridge, SD) |
Extreme Wind Producer (started in southeast Montana)
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| August 11, 2026, 651 PM MDT KUDX 0.5 Base Reflectivity Image | August 11, 2026, 651 PM MDT KUDX 0.5 Base Velocity Image (at the time of 111 MPH wind gust 13 miles northeast of Newell, SD | August 11, 2026, 926 PM MDT KUDX 0.4 Base Velocity Image (near the time of the 102 MPH wind gust 4 miles east of Cactus Flat, SD) | August 11, 2026, 1055 PM MDT / 1155 PM CDT KUDX 0.4 Base Reflectivity Image (at the time of the 96 MPH wind gust near White River, SD causing significant damage) |
August 11, 2026, 100 PM MDT to August 12, 2026, 100 AM MDT Radar Animation (click to view full resolution)
Supercell Tracks
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| 24-hour Lightning Flashes ending August 12, 2026, at 6am MDT. The tracks of the two supercells are very clear. | Map of Severe Thunderstorm Warning Polygons for both supercells with Storm Reports |
Social Media
Here are some notable social media posts depicting these powerful supercells. Note: These embedded posts may not display in some browsers.
Best structure I’ve seen all year in Castle Rock, SD yesterday #sdwx pic.twitter.com/jzUl0ntzFX
— MesoMedia (@MesoMedia_X) August 12, 2026
Solid organization and lowering cloud base ongoing north of Hermosa, SD #Supercell #SDwx 3:00 PM @NWSRapidCity pic.twitter.com/Sq7UjPHiHa
— Falcon Storm Chasing (@FalcnStormChase) August 11, 2026
2 miles south of pine ridge south dakota @NWSRapidCity #sdwx pic.twitter.com/WQlndofhCk
— Dan (The Iceman) Fitts (@Dan_Fitts) August 12, 2026
Storm Reports
All storm reports are preliminary. Click for interactive map. ...MAXIMUM OBSERVED WINDS SORTED BY MAGNITUDE... LOCATION MAX WIND COMMENTS MPH 13 NE Newell SD 111 651 PM 8/11/2026 4 E Cactus Flat SD 102 925 PM 8/11/2026 1 S White River SD 96 1055 PM 8/11/2026 6 SW Castle Rock SD 92 640 PM 8/11/2026 7 ESE Rosebud SD 90 1115 PM 8/11/2026 2 E Cottonwood SD 84 930 PM 8/11/2026 4 WNW Cedar Butte SD 83 1030 PM 8/11/2026 Wewela SD 83 1227 AM 8/12/2026 3 NW Wasta SD 79 836 PM 8/11/2026 3 S Creighton SD 76 840 PM 8/11/2026 8 S Hoover SD 75 634 PM 8/11/2026 3 E Philip SD 74 942 PM 8/11/2026 Interior SD 70 924 PM 8/11/2026 Wasta SD 69 845 PM 8/11/2026 7 WSW Hoover SD 69 621 PM 8/11/2026 17 W Castle Rock SD 67 620 PM 8/11/2026 1 NE Midland SD 66 1010 PM 8/11/2026 12 WSW Castle Rock SD 66 629 PM 8/11/2026 2 E Elm Springs SD 66 805 PM 8/11/2026 Union Center SD 65 735 PM 8/11/2026 9 SSW Castle Rock SD 64 641 PM 8/11/2026 Philip SD 63 944 PM 8/11/2026 1 NNE Rosebud SD 63 1209 AM 8/12/2026 27 WNW Castle Rock SD 63 550 PM 8/11/2026 9 ENE Belvidere SD 61 1025 PM 8/11/2026 15 SSE Mission SD 61 1137 PM 8/11/2026 4 SSE Hoover SD 61 629 PM 8/11/2026 2 S Redig SD 60 553 PM 8/11/2026 12 ENE Buffalo Gap SD 60 507 PM 8/11/2026 9 ENE Camp Crook SD 59 509 PM 8/11/2026 6 WSW Fairpoint SD 59 725 PM 8/11/2026 5 ESE Owanka SD 58 854 PM 8/11/2026 5 ENE Wanblee SD 58 955 PM 8/11/2026 8 S Saint Francis SD 56 1219 AM 8/12/2026 8 S Wall SD 56 920 PM 8/11/2026 2 SSW Enning SD 54 737 PM 8/11/2026 4 SSE Witten SD 53 1202 AM 8/12/2026 3 WSW Fairburn SD 52 443 PM 8/11/2026 2 S Newell SD 52 653 PM 8/11/2026 4 SE Wasta SD 52 830 PM 8/11/2026 7 E Wanblee SD 52 1001 PM 8/11/2026 10 WSW Ottumwa SD 52 945 PM 8/11/2026 9 S Camp Crook SD 51 510 PM 8/11/2026 3 NNW Scenic SD 51 849 PM 8/11/2026 11 SW Parmelee SD 51 1105 PM 8/11/2026 Dwtn Spearfish SD 50 714 PM 8/11/2026 3 N Redig SD 50 550 PM 8/11/2026 3 W Union Center SD 50 728 PM 8/11/2026 ...MAXIMUM HAIL SIZE SORTED BY MAGNITUDE... LOCATION MAX SIZE COMMENTS IN/S/ 6 NW Oglala SD 4.00 548 PM 8/11/2026 7 NNW Oglala SD 3.90 542 PM 8/11/2026 2 SSW Hermosa SD 3.60 335 PM 8/11/2026 Hermosa SD 3.50 330 PM 8/11/2026 3 SSW Hermosa SD 3.40 335 PM 8/11/2026 4 W Hermosa SD 3.25 321 PM 8/11/2026 2 SW Hermosa SD 3.00 333 PM 8/11/2026 Oglala SD 3.00 554 PM 8/11/2026 4 WNW Hermosa SD 3.00 319 PM 8/11/2026 2 WNW Oglala SD 3.00 554 PM 8/11/2026 7 W Hermosa SD 3.00 410 PM 8/11/2026 Pine Ridge SD 3.00 618 PM 8/11/2026 1 SE Oglala SD 3.00 555 PM 8/11/2026 13 E Buffalo Gap SD 3.00 516 PM 8/11/2026 1 SSE Pine Ridge SD 3.00 620 PM 8/11/2026 4 NNW Pine Ridge SD 2.75 614 PM 8/11/2026 1 W Pine Ridge SD 2.75 619 PM 8/11/2026 1 E Hayward SD 2.75 315 PM 8/11/2026 8 NNW Oglala SD 2.75 539 PM 8/11/2026 1 WNW Hermosa SD 2.75 328 PM 8/11/2026 4 WSW Fairburn SD 2.75 437 PM 8/11/2026 5 WNW Hermosa SD 2.75 318 PM 8/11/2026 1 S Pine Ridge SD 2.75 626 PM 8/11/2026 1 S Oglala SD 2.75 557 PM 8/11/2026 Rockerville SD 2.50 255 PM 8/11/2026 5 NNW Pine Ridge SD 2.50 610 PM 8/11/2026 3 NNW Johnson Siding SD 2.50 230 PM 8/11/2026 1 S Rockerville SD 2.50 302 PM 8/11/2026 1 SSW Hermosa SD 2.25 335 PM 8/11/2026 2 SSE Rockerville SD 2.00 303 PM 8/11/2026 4 ENE Johnson Siding SD 1.75 232 PM 8/11/2026 3 ENE Rockerville SD 1.75 259 PM 8/11/2026 4 N Johnson Siding SD 1.75 231 PM 8/11/2026 3 NNE Johnson Siding SD 1.75 231 PM 8/11/2026 12 ENE Buffalo Gap SD 1.75 509 PM 8/11/2026 3 ESE Hermosa SD 1.50 327 PM 8/11/2026 2 W Black Hawk SD 1.50 234 PM 8/11/2026 3 W Fairburn SD 1.50 439 PM 8/11/2026 1 NNW Nemo SD 1.50 224 PM 8/11/2026 1 NE Cedar Pass SD 1.25 932 PM 8/11/2026 2 NE Rockerville SD 1.25 255 PM 8/11/2026 3 WNW Hill City SD 1.00 545 PM 8/11/2026 8 WSW Ladner SD 1.00 440 PM 8/11/2026 1 N Redig SD 1.00 550 PM 8/11/2026 6 SE Fairburn SD 0.88 455 PM 8/11/2026 4 NW Dwtn Rapid City SD 0.75 239 PM 8/11/2026
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