September 21, 2010: Hail in Walworth County

A cold front moving through the region was the focus for development of a broken line of thunderstorms ahead of the front during the afternoon and evening. The combination of ascent with a short wave impulse passing over the region, daytime heating, low-level moisture inflow on a 40 knot west southwest low-level jet, and steep low to mid-level lapse rates produced severe thunderstorms with large hail and damaging wind gusts. Additionally, the storms produced a brief, EF0 tornado in Rock County, southeast of Janesville.