Hail in Clay County, Illinois

A deep surface low pressure system was positioned north of the Great Lakes on the evening of May 4th, with an associated cold front pushing into and across central Illinois. The airmass ahead of the front was characterized by moderate instability and steep mid-level lapse rates, which supported large hail. Two areas of thunderstorms formed, the first being isolated supercells that tracked near and south of I-70 well ahead of the cold front. The other area was a broken line of storms that developed along the front and advanced southward across the region during the late evening. Both sets of storms produced large hail, the largest of which was ping pong ball-sized in Clay County.