The National Weather Service offices in both Milwaukee and Chicago surveyed damage Tuesday morning and afternoon following the derecho event that moved through northern Illinois and southern Wisconsin Monday. While most of the damage was caused by straight line winds, there were several areas that the National Weather Service wanted to survey as possible damage from tornadoes.
The Chicago National Weather Service did conclude that two tornadoes touched down in Rockford, one on the southwest side and one on the northeast side. The first confirmed tornado occurred southwest of Rockford near the intersection of Pierpont Ave and Montague Rd a little before 2:40pm. This was a brief EF-0 tornado with peak winds of 75 mph. It traveled northeast for 1.5 miles before lifting near the intersection of Ferguson and Loomis Streets. Damage along its path was confined to mostly trees.
The second tornado touched down northeast of downtown Rockford, just north of Rockford University at approximately 2:47pm and traveled northeast. It was on the ground for 9.2 miles before lifting near Caledonia. This tornado was rated as an EF-1 with peak winds of 100 mph. There was significant tree damage consistent with EF-1 wind speeds (86-110 mph) in a localized area near Rock Valley College, with sporadic damage after. Both Rockford tornadoes occurred with the same supercell thunderstorm.
A third tornado was confirmed in McHenry County south of Marengo a little after 3pm. This was also rated an EF-1 with peak winds of 95 mph. It was on the ground for 5.7 miles as it traveled northeast from Harmony Rd, southwest of I-90, before lifting near Dunham Rd. Most of the damage produced by this tornado was to trees and farm buildings. Thankfully, none of the tornadoes caused any injuries.
There were also tornadoes confirmed in Chicago, as well Walworth and Kenosha counties in southeast Wisconsin. The National Weather Service stated there were still areas they wanted to investigate that had potential tornadic activity. Those additional surveys will likely be done in the days to follow. As it stands Tuesday evening, there have been 7 reported tornadoes in Illinois from Monday’s derecho event. It’s possible that number may grow as additional surveys are conducted.