Hail in Coles County, Illinois

An outflow boundary interacting with a seasonably warm and moist airmass triggered a line of strong to severe thunderstorms across western Illinois during the morning of May 18th. The storms pushed eastward across central Illinois, resulting in periodic damaging wind gusts mainly north of the I-70 corridor. While the leading edge of the storms swept eastward into Indiana, the trailing flank became parallel with the prevailing flow and led to training cells and heavy rainfall along and south of I-70. Widespread amounts of 2 to 4 inches were common, with portions of southern Effingham County and northern Clay County picking up in excess of 5 inches. An observer 3 miles north-northwest of Bible Grove in far southern Effingham County measured 5.50. As a result of the excessive rainfall over the course of just a couple hours, flash flooding occurred across this area.