"Violent" means tornado winds could be 166 mph or greater, with ratings of EF-4 or EF-5. These tornadoes are often "long-track," which means they may be on the ground for at least 25 miles. One tornado that was tracked in central Alabama Thursday evening may have been on the ground for roughly 100 miles, the National Weather Service's Birmingham office said.
The five confirmed deaths were in Calhoun County, local officials said. They include three people from one family and a man in Ohatchee and a woman in Wellington, according to the Calhoun County Medical Examiner's Office. A 13-year-old girl in the Ohatchee family survived but lost her mother and grandparents, according to Calhoun County Sheriff Matthew Wade. Another male family member also survived, he said.
There are also reports of multiple injuries in the Ohatchee area, according to Tiffany DeBoer, spokesperson for the county's Emergency Management Agency.
The search and rescue efforts in the county are ongoing, involving around 200 first responders.
In Shelby County, home to Birmingham, some homes have been completely destroyed, Sheriff John Samaniego said.
"Our priority at the moment is identifying those citizens in need of emergency medical attention," the sheriff said. "We will then work with our partnering agencies to provide needed resources to our residents who are displaced. This search and outreach effort will continue throughout the night and into the early morning hours."
A small number of people were injured in the Eagle Point neighborhood of Shelby County, Cahaba Valley Fire Chief Barry Casey said.
Centreville in Bibb County sustained major damage, according to Mayor Mike Oakley, with multiple homes completely destroyed. The local airport was also heavily damaged. "Airplanes were tossed like toys," Oakley said.
In Pelham, a city in Shelby County, approximately 60 homes have been damaged, about a third sustaining major damage, authorities said. About 200 people sought shelter at the local middle school during the storm. No injuries have been reported. A curfew remains in place through 6 a.m. in the impacted areas.
A police officer was struck by lightning in Florence while responding to flood conditions, authorities said. The officer was readjusting a barricade in standing water when he was hit, according to Police Deputy Chief Mike Holt. The officer called in his location over the radio, and responding officers took him to a local medical center, the chief said. The officer suffered burns on his back but is expected to be OK, Holt said.
There have been 14 reported tornadoes in Alabama and Mississippi as of Thursday night. Both states are in a tornado threat zone, along with parts of Tennessee, Georgia, Kentucky, Indiana and Illinois.
A new tornado watch was issued Thursday night for parts of Georgia, including Atlanta, until 2 a.m. local time.
A tornado was confirmed at 12:30 p.m. local time near Moundville, Alabama, outside of Tuscaloosa -- the same spot struck by a tornado eight days ago.
Just before 2 p.m. local time, an extremely large tornado was confirmed in Vandiver, Alabama, outside of Birmingham.
Alabama Gov. Kay Ivey has issued a state of emergency for 46 counties, and announced that the health department has rescheduled its Alabama National Guard vaccination clinic in Hale County due to the storm.
In Mississippi, more than two dozen people have taken shelter at an elementary school in Lowndes County ahead of the severe weather. Two other schools, each of which can hold about 400 people, also are open as shelters, the Lowndes County emergency management director told ABC News.
All shelters are providing hand sanitizer and masks, enforcing social distancing and checking people's temperatures.
First lady Jill Biden postponed a trip to Alabama on Friday due to the storms. She was to help tout the Biden administration's COVID relief bill in Birmingham and Jasper.
Multiple rounds of intense thunderstorms also are expected in the afternoon and evening across eastern Mississippi, northern Alabama and much of Tennessee, from Nashville to Knoxville.
Damaging winds are expected, especially in Tennessee and Kentucky. Wind gusts could reach 80 mph, and very large hail is possible.
By midnight, storms with damaging wind gusts will be moving through Atlanta and into parts of the mid-Atlantic and Ohio Valley.
The storms could also bring heavy downpours, so people should be mindful of possible flash flooding.
ABC News' Christopher Donato, Will Gretsky, Rachel Katz, Elwyn Lopez and Darren Reynolds contributed to this report.