Tornado Alley
Although the official boundaries of Tornado Alley are not clearly defined, its core extends from northern Texas, Oklahoma, Kansas, Nebraska, into South Dakota. States such as Missouri, Iowa, Minnesota, Wisconsin, Illinois, Indiana, and western Ohio are sometimes included in Tornado Alley. Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian prairies.
Tornado outbreak sequence of April 19–24, 2011
The tornado outbreak sequence of April 19–24, 2011 was an extended period of significant tornado activity that began on April 19th, 2011 and ended on April 24, 2011. It affected the Midwest and Southern United States. The outbreak produced an EF4 tornado that tore through the St. Louis metropolitan area. Other tornadoes caused damage in Illinois, Indiana, and Ohio. Amazingly, no fatalities were reported in this outbreak. However, it was later followed less than 48 hours later by the largest tornado outbreak in the history of the United States.