Hail in Whiteside County, Illinois

A strong cold front coupled with an anomalously warm air mass (highs in the 70s that broke records for the day, month, and season) and sufficient moisture set the stage for the development of severe thunderstorms across portions of northwest Illinois between 4 PM and 7 PM on Tuesday, February 27.

Storms quickly became severe after they developed across northwest Illinois during the late afternoon. As they tracked eastward, they produced hail up the size of golf balls, most notably around the Geneseo, IL and Atkinson, IL vicinities, and one confirmed EF1 tornado in the vicinity of Annawan, IL around 6 PM. A Tornado Warning was issued near 5:30 PM for this storm (NWS headline map at that time).

Storms progressed east across northern Illinois during the evening with several more tornadoes in the NWS Chicago County Warning Area. The storms were soon followed by strong non-thunderstorm winds gusting 40-50 MPH with the cold front passage.