Tornado in Lyon County, Iowa

A tornado track was identified in corn fields using drone images. Other than the narrow convergent path in the corn, there were no damage indicators to determine a rating. The average path width was 20 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.