A small but damaging outbreak of 15 tornadoes impacted the Southeast on February 7, 2017. The most damaging tornado of the outbreak was a large and powerful EF3 tornado. The tornado caused considerable damage along its path and left approximately 10,000 homes without electricity. 33 injuries occurred in the area after the tornado hit near Chef Menteur Highway with hundreds of structures sustaining moderate to significant damage along the ten-mile path. In response to the disaster, Governor John Bel Edwards declared a state of emergency.
Other destructive and strong tornadoes occurred on this day as well, including an EF1 tornado that killed a man near Donaldsonville, Louisiana and another EF3 tornado that injured three and caused considerable damage to homes, trees, and power lines in Livingston Parish, Louisiana. Overall, the outbreak killed one and injured 40.
Meteorological synopsis
On February 4, the Storm Prediction Center (SPC) outlined a severe weather threat area across portions of the Ohio Valley southward into the northern Gulf Coast states. A corresponding Slight risk of severe weather was issued the following day from central Indiana and Ohio to northern Mississippi and Alabama, encompassed within a larger Marginal risk. Little change occurred for the 07:00 UTC Day 2 outlook, but the Marginal risk was eventually shifted to encompass portions of eastern Louisiana on the 17:30 UTC forecast. Early on February 7, the SPC expanded the Slight risk area and subsequently introduced a small Enhanced risk for portions of eastern Louisiana, southern Mississippi, southwestern Alabama, and the extreme western Florida Panhandle, although its intent was for the potential for large hail instead of significant tornadoes.
On February 7, an intensifying southern-stream shortwave trough progressed eastward from the southern Great Plains to the lower Mississippi Valley. Ahead of the trough, strong low- to mid-level winds transported abundant moisture northward from the Gulf of Mexico, with dewpoints reaching to lower to mid 60s °F. The combination of southwesterly flow and abnormally cold mid-level temperatures—approximately —helped to destabilize the atmosphere, with maximum Convective Available Potential Energy values in the range of 1500–2000 j/kg. Veering winds—winds that turn clockwise with height—acted to lengthen hodographs and provide significant directional wind shear, with 0–6 km shear of and 0–3 km storm relative helicities of 200–300 m2/s2. Meanwhile, incredibly steep mid-level lapse rates near or above 8 C/km overspread the risk area. The increasingly conducive environment prompted the SPC to issue a tornado watch across southern Louisiana and Mississippi, valid from 7:55 a.m. CST (13:55 UTC) to 2:00 p.m. CST (21:00 UTC); forecasters assessed a 50% chance of two or more tornadoes in the watch box, but only a 20% chance of one or more strong (EF2+) tornadoes.