As many as ten tornadoes were spotted Wednesday afternoon as severe storms threaten nearly a third of the country. Tornado watches and warnings were issued in at least ten states.
Jim Belles, a meteorologist with the National Weather Service in Memphis, Tennessee, confirmed a tornado had touched down Wednesday in Coahoma County in northwest Mississippi.
CBS affiliate WREG in Memphis reported a large tornado plowed through Clarksdale, Mississippi and appeared to be on the ground for about ten minutes, toppling a tractor trailer onto its side and destroying homes.
No injuries were immediately reported.
Clarksdale Mayor Bill Luckett said the only confirmed casualty was a dog killed by storm debris, but as many as 20 homes may have been hit Wednesday.
Luckett said the town is opening its civic center to offer shelter for anyone who needs it. The storm also wreaked havoc at a small airport where planes were overturned.
Luckett called the damage horrific, including sheet metal wrapped around trees.
The severe weather turned deadly earlier Wednesday when a tree blew over onto a house in Arkansas, killing an 18-year-old woman and trapping a one-year-old child inside, authorities said. Rescuers pulled the toddler safely from the home.
The biggest threat for tornadoes was in a region of 3.7 million people in Mississippi, Tennessee and Arkansas and parts of Missouri, Illinois and Kentucky, according to the national Storm Prediction Center in Oklahoma.
The center issued a "particularly dangerous situation" alert for the first time since June 2014, when two massive EF4 twisters devastated a rural Nebraska town, killing two people.
The greatest risk for a few "intense, long-tracked tornadoes" will be through Wednesday night. Television images showed the tornado in Mississippi appeared to be on the ground for more than 10 minutes.
About 120 miles east of the tornado, Brandi Holland, a convenience store clerk in Tupelo, Mississippi, said people were reminded of a tornado that damaged or destroyed more than 2,000 homes and businesses in April 2014.
"They're opening all our tornado shelters because they say there's an 80 percent chance of a tornado today," Holland said.
Elsewhere, skiers on the slopes out West got a fresh taste of powder and most people in the Northeast enjoyed spring-like temperatures as they finished up last-minute Christmas shopping.
"It's too warm for me. I don't like it. I prefer the cold in the winter, in December. Gives you more of that Christmas feel," said Daniel Flores, a concierge from the Bronx, his light jacket zipped open as he shopped in Manhattan with his three children.
Only about half of the nation, mostly in the West, should expect the possibility of a white Christmas.
In Alabama, heavy rains overnight left some downtown Mobile streets flooded during the morning rush hour.
Across Mobile Bay in the small town of Loxley, Mandy Wilson watched the angry gray sky and told drivers to be careful as she worked a cash register at Love's Travel Stop.
"It's very ugly; it's very scary," Wilson said. "There's an 18-wheeler turned over on I-10. There's water standing really bad. It's a really interesting way to spend Christmas Eve eve."
In parts of Georgia, including Atlanta, a flood watch was posted through Friday evening as more than 4 inches was expected, the National Weather Service said.
The threat of severe weather just before Christmas is unusual, but not unprecedented, said Greg Carbin, a meteorologist at the national Storm Prediction Center. On Christmas Day in 2012, a storm system spawned several tornadoes, damaging homes from Texas to Alabama.
Emergency officials in Tennessee worried that powerful winds could turn holiday yard decorations into projectiles, the same way gusts can fling patio furniture in springtime storms, said Marty Clements, director of the Madison County Emergency Management Agency in Jackson, the state's largest city between Memphis and Nashville.
"If you go through these neighborhoods, there are a lot of people very proud of what they've put out and they've got stuff everywhere -- all these ornaments and deer and everything else," Clements said. "They're not manufactured to withstand that kind of wind speed, so they become almost like little missiles."
Two tornadoes hit central Louisiana on Monday, injuring a man whose travel trailer flipped over. The Lake Charles office of the National Weather service said both were EF-1 twisters with peak winds of 95 mph. The tornadoes uprooted trees, damaged homes and cars.
In Arkansas, Pope County Sheriff Shane Jones said the 18-year-old woman was killed when a tree crashed into her bedroom. The woman and her 1 ½-year-old sister were sleeping in a bedroom of the house near Atkins about 65 miles northwest of Little Rock, when winds uprooted the tree that crashed through the roof.
"It's terrible that this happened, especially at Christmas," Jones said.
Forecasters said by Wednesday night, the severe weather threat could shift east into the southern Appalachian Mountain region.
Once the strong storms clear out, warm temperatures were expected. Highs in Atlanta and Charlotte, North Carolina, on Christmas Eve were forecast to be in the mid-70s.
© 2015 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.