April 17

On April 13, the Storm Prediction Center (SPC) outlined a broad swath of the Central United States for the potential for severe thunderstorms four days later.^[2] The general threat area was further expanded on April 14, and a heightened risk was introduced from eastern Texas northward into Iowa, indicative of higher confidence of a severe weather outbreak.^[3] The next day, a day 3 Enhanced risk was introduced across portions of North Texas, southeastern Oklahoma, and southwestern Arkansas,^[4] where supercell thunderstorms capable of producing very large hail were expected. This threat level was maintained going into the event. As a shortwave trough moved into the Central Plains on the afternoon of April 17, strong forcing helped to eliminate the cap across the region. An unstable atmosphere, characterized by mid-level Convective Available Potential Energy (CAPE) values of 1,500–2,500 J/kg, strong wind shear, and very steep mid-level lapse rates of 8.5–9 C/km,^[5] led to the formation of discrete supercell thunderstorms along a stationary front across the Texas and Oklahoma panhandles, as well as southern Kansas. Sporadic large hail and landspout tornado reports were received before the storms congealed into a line,^[6] transitioning the main severe threat to damaging wind gusts.^[7] Less concentrated activity occurred throughout the region, including a thunderstorm that produced five consecutive minutes of winds above 58 mph (93 km/h), and a peak gust of 74 mph (119 km/h), in Denton, Texas.^[8]

April 18

As the SPC introduced a day 5 threat area across the Central United States valid on April 17, the organization also outlined a large day 6 region across portions of the Midwestern states, Mississippi Valley, and Appalachia.^[2] A day 3 Slight risk was originally introduced from the central Gulf Coast north into southern Illinois, but a rare mid-afternoon update outlined an Enhanced risk across eastern Louisiana into southern Mississippi.^[9] It was later expanded eastward to encompass much of Alabama as well as the Florida Panhandle.^[10] In their 16:30 UTC update on April 18, the SPC contemplated upgrading portions of the risk area to a Moderate risk (driven by the chance for tornadoes), but ultimately deferred due to questions surrounding the characteristic of expected storms.^[11] As the aforementioned, well-defined shortwave trough progressed eastward into the lower Mississippi Valley, a mesoscale convective vortex organized over west-central Mississippi.^[12] Embedded circulations and semi-discrete supercell structures within this complex led to 44 confirmed tornadoes, the strongest of which caused high-end EF2 damage in Morton, Mississippi.^[13] This ties the Hurricane Rita tornado outbreak as the largest outbreak in Mississippi state history.^[14] As the squall line tracked east, numerous reports of damaging wind gusts were received across the Southeast United States.^[15]

April 19

The first indications for organized severe weather on April 19 came six days prior, when the SPC introduced a day 7 threat area from Maryland southward into southern Florida.^[2] This outlook was maintained over subsequent days, transitioning to a day 3 Enhanced risk across portions of northeastern South Carolina, eastern North Carolina, and southeastern Virginia on April 17.^[16] The next day, the highest risk area was extended southward into Georgia and Florida.^[17] By the morning of April 19, a Moderate risk was introduced, stretching from eastern South Carolina into south-central Virginia.^[18] Along the leading edge of strong forcing, a severe squall line developed across central Florida northward into southern Virginia,^[19] leading to hundreds of damaging wind reports throughout the region.^[20] Ahead of this line, multiple long-lived supercells tracked across the Carolinas and into southern Virginia, with others developing as far north as Pennsylvania. Several strong tornadoes touched down within this corridor, where mid-level CAPE reached 1,000 J/kg and low-level wind shear profiles became conducive for tornadoes.^[21] Overall, 12 tornadoes touched down in North Carolina, the state's sixth largest outbreak on record in a single day.^[22] Meanwhile, 16 tornadoes were confirmed in Virginia, the state's third largest outbreak in a 24-hour period, surpassed only by the Hurricane Ivan tornado outbreak and the 1993 Virginia tornado outbreak.^[23] Into the evening, a loss of daytime heating led to a diminishing of the severe weather potential as thunderstorms shifted eastward into the Atlantic Ocean.^[24]

April 17 event

April 18 event

April 19 event