The storms could bring strong tornadoes or winds of more than 75 mph, heavy rain, quarter-sized hail and dangerous lightning in Louisiana and Mississippi, the National Weather Service said. The greatest risk is in areas north of Interstates 10 and 12, with the worst storms likely along and southeast of a line from Winnsboro, La., to Jackson and DeKalb, Miss., according to the weather service's Jackson office.
"We understand that most people will be focusing on the holiday," said Mississippi Gov. Phil Bryant. "Please plan now for how you will receive a severe weather warning, and know where you will go when it is issued. It only takes a few minutes, and it will help everyone have a safe Christmas."
In Alabama, the director of the Emergency Management Agency, Art Faulkner, said he was briefing both local officials and Gov. Robert Bentley on plans for dealing with a possible outbreak.
Forecasters said storms would begin near the coast and spread north through the day, bringing with them the chances of storms, particularly in central and southwest Alabama. No day is good for severe weather, but Faulkner said Christmas adds extra challenges because people are visiting unfamiliar areas. Also, people are more tuned in to holiday festivities than their weather radio on a day when thoughts typically turn more toward the possibility of snow than twisters, he said.
"We are trying to get the word out through our media partners and through social media that people need to be prepared," Faulkner said
Meteorologists also recommended getting yards ready Monday, bringing indoors or securing Christmas decorations, lawn furniture and anything else that high winds might rip away or slam into a building or car.
"Make sure they're all stable and secure — that there's not going to be any loose wires blowing around and stuff like that," or bring them inside, said Joe Rua, with the National Weather Service in Lake Charles, where storms were expected to roar in from Texas after midnight.
The bad weather was expected from a storm front moving from the West Coast crashing into a cold front, said weather service meteorologist Bob Wagner of Slidell.
"There's going to be a lot of turning in the atmosphere," he said.
Ten storm systems in the last 50 years have spawned at least one Christmastime tornado with winds of 113 mph or more (F-2) in the South, Chris Vaccaro, a National Weather Service spokesman in Washington, said in an email. The most lethal were the storms of Dec. 24-26, 1982, when 29 tornadoes in Oklahoma, Missouri, Arkansas, Tennessee and Mississippi killed three people and injured 32; and those of Dec. 24-25, 1964, when two people were killed and about 30 people injured by 14 tornadoes in seven states.
In the New Orleans suburb of Metairie, Timothy J. Babin said the 10 or so wire Christmas sculptures in his yard and more than 180 plastic figures in his mother's yard are ready for just about any storm. Each one is staked down when it's set out, he said.