EF1 tornado in Lyon County, Iowa

A tornado spun up approximately 1 mile east-northeast of Alvord just north of 210th Street and around one-half mile west of Fig Avenue. The tornado traveled southeast one-half mile to Fig Avenue where it destroyed a small shed and heavily damaged an abandoned farmstead, including a grove of old trees. A distinct convergent path was noted in the corn just north of the farmstead. One mile farther east-southeast, the tornado destroyed a barn along Fir Avenue. After traveling another one-half mile through fields, the tornado lifted east of Fir Avenue. The tornado was rated EF1 with an estimated maximum wind gust of 110 mph. The average path width was 100 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.