A regional outbreak of severe storms and possible tornadoes rippled across the South on Wednesday and was expected to continue on Thursday in parts of Georgia and the Carolinas, according to the National Weather Service.
Tornado warnings had been in effect across Mississippi and Alabama on Wednesday afternoon, according to Bill Bunting, chief of forecast operations at the service’s Storm Prediction Center. There were reports of damaged homes and farms in Wayne County, Miss., and wind damage to structures and trees in Sumter County, Ala., on Wednesday.
A “few dozen thunderstorms” were occurring across the southeastern United States, Mr. Bunting said. “We expect them to become stronger and more intense as we move through the next several hours, well into the nighttime hours,” he added.
He said he expected each thunderstorm to produce one tornado. The storms were set to bring winds over 100 miles per hour, as well as hail ranging in size from golf ball to baseball.
On Wednesday night, about 38,000 people had lost power across Mississippi, Louisiana and Alabama, according to PowerOutage.us, which aggregates live power data from utilities across the United States.
On Thursday, the storms could continue to produce tornadoes, wind damage and large hail in parts of Georgia, South Carolina and North Carolina, the Weather Service said.
The warning of a second day of powerful storms came after the Weather Service had issued a “particularly dangerous situation” tornado watch for parts of Louisiana, Arkansas and Mississippi on Wednesday until 7 p.m., indicating “a potential for multiple strong, long-track tornadoes.”
More than 2.7 million people had been at high risk from the storms on Wednesday, mostly in Mississippi and Alabama, it said, with an additional 5.6 million people at moderate risk. On Wednesday night, the Weather Service said, the potential for significant tornadoes continued, with much of the greatest risk in Alabama.
Jackson, Miss.; Birmingham, Ala.; and Tallulah, La., were among the cities at risk of damage from the storm, the Weather Service said.
A winter storm hit Jackson in February, leaving more than 70 percent of the city’s water customers under a notice to boil water for weeks. The notice was lifted last week for well-water customers and on Wednesday for surface-water customers. The rash of storms this week could again threaten the city’s water systems.
Another tornado watch was issued for parts of Oklahoma, Missouri and Arkansas until 8 p.m. Central time on Wednesday, warning of lime-size hail, potential tornadoes and isolated wind gusts up to 65 miles per hour.
“This event is really just getting started,” Mr. Bunting said, adding, “It’s going to be a long evening.”
With the storms hitting some areas well after dark, “you can’t see storms approaching very effectively,” Mr. Bunting said, advising people to be prepared and take action when warnings are issued and “not wait until they can see the danger.”
He said that the Weather Service and local meteorologists had been warning residents since this weekend about the storms.
“For most areas, there will be more than one round of thunderstorms,” he said. “It’s important not to let your guard down after one storm passes.”
The storms will most likely bring “substantial” power outages, downed trees and flooding, he said, adding that structural damage from the “intense, long-track tornadoes” was perhaps the biggest concern.
An “initial round” of tornadoes was expected to continue across Alabama on Wednesday afternoon, the Weather Service said, as a separate cluster was set to develop over northeast Louisiana before spreading east, hitting Mississippi and Alabama — the second round of storms to hit the area — Wednesday evening.
People in areas where tornado warnings are issued should shelter on the lowest floor of their homes and cover themselves with a mattress or pillow, as well as a helmet if one is available, to decrease the risk of injury, Mr. Bunting said.
Michael Levenson contributed reporting.