Tornado Alley
It has also been asserted that there are numerous Tornado Alleys. In addition to the Texas/Oklahoma/Kansas core, such areas include the Upper Midwest, the lower Ohio Valley, the Tennessee Valley and the lower Mississippi valley. Some studies suggest that there are also smaller tornado alleys located across the United States.
Tornado outbreak of April 9–11, 2011
On April 10, another moderate risk was issued. A PDS Tornado Watch was issued for parts of Minnesota, Michigan, and Iowa, as well as most of Wisconsin. With 16 confirmed tornadoes in Wisconsin, the outbreak ranks as the largest single-day event in April in the state. Severe damage occurred in the towns of Merrill, Kaukauna, and Cottonville. On the evening of April 10, a number of tornado watches and warning were issued stretching from southern Oklahoma to Sault. Ste. Marie, Michigan as well as central Ontario which became Canada's first tornado watch of the season. Thunderstorm watches and warnings were also reported as far away as northern and northwestern Ontario.
Accompanying the tornadoes, large hail and high winds also impacted parts of the Midwest. Initially, these events associated with the outbreak were confined to Iowa and parts of Nebraska and Minnesota on April 9. In Iowa, hail was measured up to in diameter, resulting in some damage to homes and cars. On April 10, a large line of severe storms produced damage from northern Minnesota southward to the Texas-Mexico border. Most damage along this line resulted from straight-line winds; however, Wisconsin, diameter hail in La Crosse broke windows, dented cars and damaged homes. Roughly 3,200 insurance claims worth $12 million were later made in the city. Elsewhere in the state, winds up to downed numerous trees and power lines and in some instances tore roofs of buildings.