August 23, 2006: Hail and a tornado across six counties

A stagnant weather pattern on August 23rd and 24th resulted in waves of heavy rain and severe thunderstorms. A warm front pushed north during the afternoon of August 23rd. A very unstable airmass with moderate shear caused thunderstorms to break out during the afternoon and continue through most of the overnight as a warm front moved north through the area. Very large hail was the primary hazard with some of the supercell thunderstorms, although there were several reports of wind damage, one tornado 2 miles south-southeast of Leland, and torrential downpours with localized flooding. Incredibly, three separate supercells tracked southeast through Sauk County almost along the same path. Each supercell had a rotating wall cloud at its base, but only one supercell managed to spin up a brief tornado. After a brief respite of only 3 hours during the morning hours of August 24th, more storms developed during the late morning and afternoon hours. More heavy rain, large hail, damaging winds, and vivid lightning resulted from these storms. Urban flooding in Dane and Kenosha counties caused a few hundred thousand dollars in structural damage. Some two-day rainfall totals across Dane County include 5.70 inches in Oregon, 5.38 inches in Cottage Grove, 3.26 inches in Middleton, 2.77 inches at Beloit College, and 2.73 inches at Madison Truax Field. Roughly 12,000 customers lost electrical power due to downed power lines and lightning strikes.