July 23, 2005: Straight-line wind across seven counties

A mesoscale convective system/derecho developed in western Minnesota during the early morning, then tracked into central Wisconsin before riding the warm front southeast into southeast Wisconsin and portions of south-central Wisconsin during the afternoon. The powerful winds generated by the storms were generally in the 52 to 56 knot range (60 to 65 mph), but peaked at hurricane-force in a couple locations . Most of the damage was characterized as toppled large trees and downed power lines as the storms raced southeast. The hardest hit areas were in Marquette, Dodge, and Jefferson counties. Widespread tree damage was reported by law enforcement in Green Lake and southern Jefferson counties. Otherwise damaging thunderstorm winds were more scattered. A barn was completely destroyed 3 miles southwest of Waupun at 1405CST where winds were estimated to have gusted around 65 knots (75 mph). Roof damage was noted on a house in Fox Lake (Dodge Co.), where winds were estimated to have gusted to around 65 knots (75 mph). As the northeastern end of the line progressed toward the Lake Michigan shoreline, it weakened substantially. However, the southwestern portion of the line progressed into Walworth, Racine, and Kenosha counties, continuing to produce areas of wind damage, before it died at the Illinois border shortly after 1530CST. Lightning during the afternoon and overnight hours damaged two buildings in Watertown (Jefferson Co.). Synoptically, the quasi-stationary front, noted in the July 21st episode, sagged south into Iowa and Illinois on the 22nd, then began to head back into Wisconsin as a warm front on the 23rd.