EF2 tornado in Gregory County, South Dakota

This was the third tornado documented by a storm chaser across Gregory County. This tornado touched down west of Whetstone Bay on the Missouri River, north of Whetstone Township Highway and to the west of County Road 57. After a very short distance, the tornado broke multiple power poles along County Road 57 as it traveled south-southeast. The tornado then traveled for 5 miles across unpopulated complex terrain with no road access, although its damage path was visible on Copernicus Sentinel data 2025. Coming out of the hills, the tornado hit a single family dwelling, with the collapse of all exterior walls among other major damage. Two nearby outbuildings were also destroyed. The tornado continued to the south-southeast for approximately 1.5 miles before it flipped a camper and destroyed an abandoned trailer on the north side of Bonesteel. The tornado lifted a few hundred yards north of Eldeen Avenue, missing the city-center of Bonesteel. The tornado was rated EF2 with an estimated maximum wind gust of 135 mph. The average path width was estimated at 125 yards.

Two distinct supercell clusters developed across central South Dakota during the late afternoon of July 28 within a highly unstable environment (MUCAPE up to 5000 J/kg) ahead of an eastward advancing surface front. The southern supercell cluster produced three tornadoes across Gregory County, the strongest of which was rated EF2.

Scattered severe wind gusts were reported across southeast South Dakota as the thunderstorms moved east before the two clusters merged near and south of Sioux Falls. Aided by increasing deep layer shear from the north, a linear structure rapidly developed with a derecho racing eastward into northwest Iowa. Winds gusted from 80 to 100 mph along the derecho's path with widespread tree and structural damage across the area. In addition, three embedded short-lived tornadoes were documented within the line of thunderstorms.