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.
NEXRAD
WSR-88D has coverage gaps below 10,000 feet (or no coverage at all) in many parts of the continental United States, often for terrain or budgetary reasons, or remoteness of the area. Such notable gaps include most of Alaska; several areas of Oregon, including the central and southern coast and much of the area east of the Cascade Mountains; many portions of the Rocky Mountains; Pierre, South Dakota; portions of northern Texas; large portions of the Nebraska panhandle; and areas near the borders of the Oklahoma and Texas Panhandles. Notably, many of these gaps lie in tornado alley. At least one tornado has gone undetected by WSR-88D as a result of such a coverage gap – an EF1 tornado in Lovelady, Texas in April 2014. As a result of the coverage gap, initial reports of tornadic activity were treated with skepticism by the local National Weather Service forecast office.