During the late afternoon and evening of April 2, 2006, a series of tornadoes broke out in the central United States. It was the second major outbreak of 2006, in the same area that suffered considerable destruction in a previous outbreak on March 11 and 12, as well as an outbreak on November 15, 2005. The most notable tornadoes of the outbreak struck northeastern Arkansas, the Missouri Bootheel, and West Tennessee, where several communitiesincluding Marmaduke, Arkansas, Caruthersville, Missouri, and Newbern, Tennessee suffered devastating damage. In total, 66 tornadoes touched down across seven states, which is the most in a single day in 2006. In addition, there were over 850 total severe weather reports, including many reports of straight-line winds exceeding hurricane force and hail as large as softballs, which caused significant additional damage in a nine-state region.
The outbreak caused 27 tornado-related deaths and caused two other fatalities from straight-line winds. It was the deadliest tornado outbreak in the United States since the tornado outbreak sequence of May 2003, which killed 48 people. Twenty-six of those deaths were caused by a single supercell thunderstorm which produced damaging and long lived tornadoes from north central Arkansas into northwest Tennessee.
Meteorological synopsis The outbreak was caused by a cold front that tracked across the central United States, triggered by a deep low-pressure area in the Upper Midwest. The warm humid air mass ahead of the cold front, along with high upper-level wind shear, produced supercells across the region. A large trough was located in the Dakotas, and another low pressure system was located in Nebraska. A small high pressure upper-level ridge pushed between the two low pressure systems. Intense diffluence was present at the jet streak, forcing winds into Kentucky, and eastern winds into South Carolina. This enhanced vertical motion in the Tennessee Valley. Steep lapse rates were evident on the Mississippi River.
The outbreak was expected to have started the previous day in the High Plains as the cold front tracked across that region. The supercells didn't really fire up as expected and only one small tornado was reported in Pawnee County, Kansas on April 1. Severe weather that day was largely restricted to significant microbursts and large hail.
The Storm Prediction Center (SPC) issued a moderate risk of severe weather for April 2, with the main risks being tornadoes and large hail. The primary risk area was the central Mississippi Valley and lower Ohio Valley up to central Illinois, where most of the tornadoes touched down. Many tornado watches – if not any PDS watches – were issued across the region. While a significant severe weather event was expected, the extreme nature caught many forecasters by surprise, based on the risk levels and the probabilities estimated by the SPC in the area primarily affected.
Farther north, the initial thunderstorm development in eastern Missouri quickly developed into a squall line, eventually becoming a derecho that produced many embedded – and generally weak – tornadoes and widespread wind damage across Illinois, Indiana, Kentucky, and Ohio. Springfield, Illinois, which was struck by two tornadoes less than a month earlier, was hit again by tornadoes and damaging straight-line winds of up to , as was the St. Louis, Missouri area. Wind damage was reported in Cincinnati, Louisville, Kentucky, and Indianapolis, among other cities.
The line of storms slowly weakened while traveling eastward, and the severe weather events dissipated later that evening.
Confirmed tornadoes