Resurging heat, with implications to Chicago's weekend weather, fueled waves of powerful thunderstorms which unleashed a half foot of rain on sections of South Dakota late Friday. The mammoth storms towered to heights of 54,000 feet and flared as hot, humid air was lifted into an unusually strong mid-summer jet stream. Shifting wind direction with height generated storm rotation -- always an ominous development. Grapefruit-sized hail bombarded Rapid City, S.D., breaking windows, and at least two small tornadoes touched down briefly near St. Francis, S.D., and Sparks, Neb. Rainfall Friday reached 5.92" at Chamberlain and 2.36" at Pierre -- both in South Dakota—3.10" at Pine Bluffs, Wyo., and 2.61" at Fessenden, N.D.
The warm front responsible for the Plains storms is eastbound. It reaches Chicago late Saturday night. Increasing clouds and SE winds off the lake today threaten potentially prolific lightning-producing thunderstorms overnight.
--By Tom Skilling, WGN-TV Chief Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
