April 3, 2011: Hail across four counties

Two rounds of thunderstorms affected southern Wisconsin on April 3rd, as low pressure moved northeast from Iowa across Wisconsin. Morning elevated thunderstorms, with warm air advection on the nose of a low-level jet ahead of the approaching low, did not produce severe weather...but a shower of small hail created icy road conditions in Dodge County, where a two-vehicle accident killed a 26 year old female and injured two others. During the afternoon hours, a warm front lifted into southern Wisconsin as the low moved into the state...with mean layer CAPE increasing to 1000 to 1500 J/kg along with strong low layer shear and deep layer bulk shear. This triggered the second round of thunderstorms in the evening that were severe, producing mainly large hail up to the size of a baseballs, along with damaging winds. Madison-based American Family Insurance Company reported 375 property claims as well as 200 vehicle damage claims in Dane and Dodge counties alone. There were probably more damaged vehicles that weren't reported to insurance companies. Roof damage caused by the golf ball to baseball-sized hail was extensive in the western suburbs of Madison, with some homes and businesses requiring whole-roof replacements. It was not possible to break up the insurance company claims and assign monetary losses to individual storms. Total monetary losses were probably in the low millions of dollars.