Late Thursday-early Friday June 12-13 a fast moving, bowing line of thunderstorms moved across north central and northeast Illinois. The line of storms produced widespread winds of 40 to 50 mph with isolated pockets of very intense, damaging winds of 60 to 100 mph. These winds downed tree limbs, power lines, and outbuildings. A house was unroofed near Kirkland.
National Weather Service Doppler radar indicated a small wind velocity couplets along the line from time to time. One in particular occurred over Boone County around 1230 AM.
Base reflectivity showing leading edge of line of thunderstorms from western and southern Boone County to eastern DeKalb County
Velocity display showing strong inbound (west to east) winds behind the line of storms and a small embedded rotational couplet south of Belvidere.
Based on information from the radar signature, reports from Boone County Emergency Management Agency and a NWS storm damage survey, it has been determined that a tornado occurred over Boone County. The tornado snapped and uprooted trees, and damaged or detstroyed farm buildings. It was rated EF1 with winds estimated to be 86 to 110 mph.
The most intense damage was along the path plotted here. There was minor damge to trees, shingles, and siding along either side of the path and a widening area of minor tree damage northeast from the end of the tornado path across I-90 to around US 20 and Garden Prairie Road.