A large complex of thunderstorms tracked through central and southeast Illinois during the night of June 3rd into the morning of June 4th. The storms initially developed in a highly unstable airmass across South Dakota and Nebraska during the afternoon of the 3rd, then moved southeastward along a stationary frontal boundary extending from northern Missouri into the central sections of Illinois and Indiana. Due to the high degree of instability and low-level wind shear in place across the Plains, the storms quickly became severe, producing numerous reports of very large hail and even a few tornadoes across Nebraska during the afternoon and early evening. The cells gradually merged into a much larger complex of showers and thunderstorms as the entire system followed the front toward the Mississippi River later in the evening. By the time the storms crossed into west-central Illinois around midnight, the threat for large hail and tornadoes had waned considerably as the primary storm mode now supported damaging wind gusts and heavy rainfall. A few bow echoes embedded within the complex produced wind gusts of 60 to 65 mph as the system tracked through central Illinois. Most notably, wind damage was reported in Jacksonville, in Latham in southern Logan County, and near Clinton in DeWitt County. In addition to the sporadic wind damage, a widespread 1 to 2-inch rainfall occurred across the area. A few locations in Springfield picked up between 3 and 3.25 rainfall in a short period of time, leading to flash flooding of several viaducts and underpasses. The storms continued southeastward through the night and eventually exited into Indiana by mid-morning on June 4th.
Here is a map of all the severe weather produced by this system. Note the numerous reports across Nebraska into Missouri.
Here is a map of the severe weather across central Illinois. By the time the storms arrived in Illinois, they were mainly wind and rain producers.
Rainfall totals from 7am June 3rd through 7am June 4th. Most locations picked up 1 to 2 inches of rain, with localized amounts in excess of 3 inches.