On February 28, the Storm Prediction Center (SPC) issued a day four risk for severe thunderstorms across a broad region of the Southeast United States stretching from northern Louisiana through northwestern Georgia. A broad slight risk was introduced the following day, and a more narrow enhanced risk was raised across portions of southeastern Alabama and southwestern Georgia later on March 2 where the threat for tornadoes, some potentially strong, appeared most likely.
GOES-16 satellite animation showing the Lee County, Alabama tornado
The severe weather prediction for March 3 came to fruition that morning as a broad mid-level cyclone in the northern jet stream pushed eastward over northern Ontario and James Bay. A series of shortwave troughs rotated the southern semicircle of this low-pressure system, with an especially well-defined shortwave progressing from the South Central United States eastward across the Appalachian Mountains and into the Atlantic Ocean. This feature led to the formation of a surface low over northern Mississippi and Alabama, aiding in the northern transport of rich and deep moisture originating from the Gulf of Mexico. Strong southwesterly low-level winds coupled with strong forcing for ascent along a trailing cold front led to the formation of a squall line stretching from the Carolinas down into portions of the Deep South. Ahead of this line, the combination of mid-level Convective Available Potential Energy of 500–1,200 J/kg, a low-level jet of 50–70 kn, and effective storm-relative helicity of 250–400 J/kg resulted in a highly unstable atmosphere that was conducive to the formation of strong tornadoes. The lack of strong convective inhibition, coupled with weak forcing, favored the formation of numerous discrete supercell thunderstorms across the Florida Panhandle, southeastern Alabama, much of central Georgia, and into South Carolina. Throughout the afternoon, numerous supercell thunderstorms that formed ahead of the squall line produced several significant and damaging tornadoes, including the violent EF4 that struck Beauregard, Alabama. As the squall line moved eastward, embedded circulations and semi-discrete structures within the line produced additional strong tornadoes before tornadic activity waned with eastward progression overnight.