The last time there was a moderate risk for severe weather this far south, during this time of year, was Christmas Day 2012, when 31 confirmed tornadoes tore across five states.
That day, an EF3 hit Pearl River, Stone, Forrest, Perry and Green counties, and an EF1 hit Mobile. Eight people were injured in Pearl River County and dozens of homes were damaged.
The National Weather Service in Slidell warned Tuesday its designation of "moderate risk" is not commonly issued, and is especially rare on the Coast.
However, bouts of severe storms are typical in February.
NWS has five risk categories for severe weather. From least to most likely, they are marginal, slight, enhanced, moderate and high.
Moderate risk means there is "an area where widespread severe weather with several tornadoes and/or numerous severe thunderstorms is likely, some of which should be intense. This risk is usually reserved for days with several supercells producing intense tornadoes and/or very large hail, or an intense squall line with widespread damaging winds."
Monday night's storm front primed the atmosphere for severe weather. The low-pressure system that followed it has measurements similar to a strong tropical storm or weak category 1 hurricane. The difference with this system is there is cool air in the center, not warm air, and the energy is spread out over a large area.
The upper atmosphere was very unstable as cool, dry air bumped into the warm, moist air near the Gulf of Mexico.