ROCKFORD, ILLINOIS — An all hazard risk will take shape across northern Illinois during the late afternoon and evening of Friday, August 21, with the National Weather Service warning of large hail, damaging wind gusts, and a few tornadoes as a second round of storms moves through after 4 PM.
Two Rounds of Storms Expected
Two separate rounds of showers and thunderstorms are forecast across northern Illinois today. The first round is expected to move south from Wisconsin into northern Illinois near and after lunchtime, but this activity should remain non-severe and will be weakening as it arrives.
That first round will fade away before a second, more dangerous round develops after 3 PM across southern Wisconsin, then pushes south into northern Illinois after 4 PM, continuing through 8 PM.
Slight Risk Corridor
The Severe Weather Outlook for Friday, August 21 shows a Slight Risk zone stretching from Rockford and DeKalb through Aurora, Moline, and Galesburg, with a broader Marginal Risk area extending to Chicago, Peoria, and Bloomington.
Greatest Tornado Risk Along I-39
While no strong tornadoes are expected with Friday’s storms, forecasters note that the greatest risk for a tornado today lies along and west of Interstate 39, a corridor that includes Rockford, DeKalb, and Galesburg.
All Hazard Threat
The second round of storms arriving after 4 PM carries an all hazard risk, meaning large hail, damaging wind gusts, and isolated tornadoes are all possible with the same line of storms as it tracks through northern Illinois into the evening hours.
Timing Recap
Communities across northern Illinois should expect the more serious severe weather threat to develop after 4 PM and continue through 8 PM, with the corridor along and west of I-39 carrying the highest tornado potential during that window.
What Residents Should Do
Residents in Rockford, DeKalb, Aurora, and surrounding northern Illinois communities should have a way to receive warnings and stay alert during the 4 PM to 8 PM window, particularly those living along and west of Interstate 39…