Time-Lapse Shows Supercell Storm in South Dakota

A supercell thunderstorm triggered flooding in Rapid City, South Dakota, on June 1, causing a 20-mile stretch of I-90 north of the city to be shut down. Nearby Piedmont was hardest hit with hail the size of a softball and reports of a funnel cloud, according to local media . No tornado was reported to have touched down. This video shows a time-lapse of the storm's clouds swirling north of Rapid City in Black Hawk. Credit: YouTube/Bonny Fleming