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.
1998 Eastern tornado outbreak
The 1998 Eastern Tornado Outbreak stands out, because it spawned an unusually high number of supercell thunderstorms, occurrences of damaging winds and hail, and tornadoes, in the central Appalachian Mountain area, where most residents were unaccustomed to experiencing such violent thunderstorms that are commonly believed to only occur in Tornado Alley in the central part of the United States.