Severe thunderstorms moved through northern Illinois and southern Wisconsin Sunday afternoon, prompting numerous severe thunderstorm warnings and one tornado warning. These storms formed ahead of an ‘MCV’, or mesoscale convective complex, that was quick to move out of southeast Iowa and into northwest Illinois. This is similar to a mini low pressure system, and can enhance the risk for severe weather ahead of it.
Thunderstorms were quick to form during the early afternoon, moving through much of the Stateline before 5pm. Reports of wind gusts to 50 mph, as well as several reports of wind damage occurred as the storms moved through. A SEVERE THUNDERSTORM WATCH remains in effect until 7pm for the following counties: Winnebago, Boone, McHenry, Ogle, Lee, DeKalb and Walworth.
Rainfall was also very heavy, causing localized flooding to occur as rainfall totals reached over one inch in many locations. There is a Flood Advisory for portions of southeast Lee County and most of DeKalb County until 8pm, and for McHenry County until 8:30pm.
The severe threat continues to decrease Sunday evening as thunderstorms move further east, however, there have been a few showers that have formed on the backside of the main line now moving through southern Boone County, with additional develop back through Ogle County. These are not expected to turn severe.