The winter weather system that has buried much of the West under record snow was racing east Thursday — on course to slam Alabama, Georgia and the Carolinas with snow and ice that authorities warned could be historic.
The National Weather Service on Thursday issued a winter storm warning beginning Friday afternoon for the northern two-thirds of Georgia, clipping the northwestern tip of South Carolina stretching through nearly the entire length of North Carolina. A chunk of east-central Alabama was added to the warning area on Thursday night.
Metropolitan Atlanta could get as much as a half-foot of snow by Saturday morning, the weather service said.
Georgia Gov. Nathan Deal pre-emptively declared a state of emergency as authorities advised residents of the entire northern half of the state to lay in enough food and water to last at least three days.
"We're looking at a significant event," said Sue Loeffler, director of the state Emergency Management Agency. "Go to the grocery store now."
Michael Thurmond, chief executive of DeKalb County in metro Atlanta, warned residents: "This can potentially be a historic weather event."
The state may have caught a break: The snow isn't expected to begin until Friday night — after Atlanta's notorious traffic has had time to clear — lessening the potential for a repeat of Snow Jam 2014, when thousands of motorists were hopelessly stranded without food and water on interstates during a paralyzing winter storm three years ago.
"We do feel fortunate that it's coming in on a Friday night, where we will have the weekend to really address the roads," said Alan Chapman, director of the Transportation Department in suburban Gwinnett County.
RELATED: February winter weather across U.S.
February winter weather across U.S.
February winter weather across U.S.
A pedestrian walks through Washington Park as light snow falls on Tuesday, Feb. 16, 2016, in Albany, N.Y. A mix of snow, sleet and freezing rain made driving conditions dicey for commuters across upstate New York, with winter storm warnings and hazardous weather advisories posted throughout the state. (AP Photo/Mike Groll)
Harry Henneman clears snow from the front steps of his daughter's house Thursday, Feb. 18, 2016, in Truckee, Calif. A storm packing rain and high winds downed power lines, toppled trees and delayed flights across California, bringing back winter weather after several days of record-heat. In the Sierra Nevada, the winter storm dropped 1 to 2 feet of light powdery snow late Wednesday, adding to a snowpack that could ease but not end drought conditions when it melts in the spring. (AP Photo/Marcio Jose Sanchez)
One of the 19 stainless steel statues of the Korean War Veterans Memorial is covered with snow in Washington, Monday, Feb. 15, 2016. Bitter cold was replaced by snow, sleet and rain Monday in the mid-Atlantic states and the South, but many residents were able to hunker down at home with federal offices and many businesses closed for Washington's Birthday. (AP Photo/Carolyn Kaster)
A vistor to the Washington Monument walks past flags flying a half-staff in honor of Supreme Court Justice Antonin Scalia on a wintry Presidents Day holiday in Washington, Monday, Feb, 15, 2016. (AP Photo/J. David Ake)
People survey damage to a business off Mississippi Highway 18 in Sylverana, Miss., Monday, Feb. 15, 2016, after severe weather affected south Mississippi. No injuries were reported in the storm. Officials are investigating reports of at least two possible tornadoes that accompanied a line of thunderstorms across central and southern Mississippi Monday. (Ryan Moore/WDAM-TV, via AP)
Frost on a window forms a heart-shaped pattern on Friday, Feb. 12, 2016, in Falmouth, Maine, where the early morning temperature dipped below zero. More cold weather is forecast for the Valentine's Day weekend in New England. (AP Photo/David Sharp)
A bus window is covered by snow and ice, Sunday, Feb. 14, 2016, in Evanston, Ill. Snow has now overspread nearly all of the Chicago Metro area early Sunday afternoon and is expected to continue into the night before ending. (AP Photo/Nam Y. Huh)
People are bundled up as they walk in cold weather, Sunday, Feb. 14, 2016, in the Queens borough of New York. Bitter temperatures and biting winds had much of the northeastern United States bundling up this weekend. (AP Photo/Mark Lennihan)
A bare tree stands in a snowy field near Freeland, Md., Tuesday, Feb. 9, 2016. The mid-Atlantic region awoke Tuesday to a mix of rain and snow. The weather service issued a winter weather advisory in the region and expected the mix to change over to snow and fall occasionally during midday hours, with rain mixing in during the afternoon south of Baltimore. (AP Photo/Patrick Semansky)
Two women run through a snow flurry Tuesday, Feb. 9, 2016, in Nashville, Tenn. (AP Photo/Mark Humphrey)
A passenger waits in the snow to board a bus at Kennedy Plaza in Providence, R.I., Monday, Feb. 8, 2016. Massachusetts, Rhode Island and eastern Connecticut, could see winter storm conditions with an accumulation of 4 to 8 inches. The heaviest snowfall is expected during Monday's morning commute through the afternoon. (AP Photo/Stew Milne)
Kevin Lord, of Sagamore Beach, Mass., braves near hurricane-force winds to inspect storm erosion on Monday, Feb. 8, 2016, along a beach near his home in Bourne, Mass. (AP Photo/William J. Kole)
Jeremy Kincaid clears a sidewalk with a snowblower after a snow storm Friday, Feb. 5, 2016, in Derry, N.H. The storm was New Englandâs biggest snowstorm so far this season, coming two weeks after a massive blizzard engulfed much of the Eastern Seaboard but largely spared Boston and points north. (AP Photo/David Goldman)
Democratic presidential candidate Hillary Clinton departs a campaign stop during a snow storm, Friday, Feb. 5, 2016, in Manchester, N.H. (AP Photo/Matt Rourke)
A snow covered playground is bathed in pink light at sunset before a town hall meeting with Republican presidential candidate Sen. Ted Cruz, R-Texas, at the Lancaster School in Salem, N.H., Friday Feb. 5, 2016. (AP Photo/Jacquelyn Martin)
WASHINGTON, DC - FEBRUARY 13: Ai Koid, 25, fights gusty wind chills and snow while walking to the bus stop at Dupont Circle in Washington, D.C., February 13, 2016, to catch a bus to New York. (Photo by Astrid Riecken For The Washington Post via Getty Images)
Andrew Story clears a sidewalk with a snowblower after a snowstorm Friday, Feb. 5, 2016, in Derry, N.H. The storm was New Englandâs biggest snowstorm so far this season, coming two weeks after a massive blizzard engulfed much of the Eastern Seaboard but largely spared Boston and points north. (AP Photo/David Goldman)
A deicing team prepares a commercial jet for safe flight during severe weather at Denver International Airport, in Colorado, early Tuesday, Feb. 2, 2016. A powerful winter storm has shut down highways in eastern Colorado, closed many schools and slowed down traffic at Denver International Airport. (AP Photo/Brennan Linsley)
Looking southwest from Reno about 20 miles away, clouds obscured the top of Slide Mountain on Monday, Feb. 1, 2016, where the Mount Rose ski resort received 18 inches of snow the day before. (AP Photo/Scott Sonner)
A plow removes snow during severe weather at Denver International Airport, in Colorado, early Tuesday, Feb. 2, 2016. A powerful winter storm has shut down highways in eastern Colorado, closed many schools and slowed down traffic at Denver International Airport. (AP Photo/Brennan Linsley)
Students on the campus of Northern Arizona University navigate through blustery weather in Flagstaff, Ariz., Monday, Feb. 1, 2016. A winter storm dropped snow on the region, closing schools and making travel difficult. (AP Photo/Josh Biggs)
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Snow was already falling over Tennessee, Kentucky and parts north, but it's when warm, wet air from the Gulf Mexico beginnings moving ashore on Friday that the real chaos is expected to begin, the National Weather Service said.
"The heavy snow will make many roads impassable and may produce widespread power outages due to the weight of the snow on tree limbs and power lines," the weather service said in a revised forecast late Thursday afternoon.
Four to 6 inches of snow may not sound like much to residents in the western third of the country, which was still being belted by record snow as high as 15 feet.
But the witches' brew of rain, sleet and snow in the South will be occurring with temperatures just below and at freezing — meaning there's a strong likelihood of a thawing-and-refreezing cycle that could coat the region in a deadly film of solid ice.
Freezing rain is "the big story here," said Kait Parker, a meteorologist for The Weather Channel. "That's a huge concern for us because that is the most dangerous and deadly type of winter weather."
Road crews across the region were preparing for a long, grueling weekend.
Maintenance workers in the South Carolina Midlands were waiting to salt most major roadways until Friday afternoon at the earliest — hoping to avoid rain that could wash the salt and brine away before it turns to snow.
"Our men and women are working as hard as they can," Alan Kozusko, a district maintenance engineer for the state Transportation Department, toldNBC station WIS of Columbia. "They've taken time away from their families, away from their usual time of work, to do the job that they do."
In Florence, in northwest Alabama, where city truck drivers also planned to head out on the streets Friday, authorities warned motorists that even freshly salted and sanded roads remain treacherous.
The city's drivers have "done this for many years, and they'll end up sliding off the road two or three times," David Koonce, manager of the city's Street Department, told NBC station WAFF of Huntsville.
"It's slick conditions out there in these spots, and we tell people [to] stay in if they can," Koonce said.
The National Weather Service predicted conditions that even it called seemingly implausible in North Carolina, where Gov.-elect Roy Cooper canceled most of the weekend's inauguration ceremonies in Raleigh, including the traditional inaugural parade.
A couple of important announcements on the Inauguration: the Inaugural Parade on Saturday is cancelled due to inclement weather.
The heaviest snow is expected north of a line along Interstate 64 from Chatham County through Raleigh and Rocky Mount, forecasters said. South and east of that line will get a mix of snow, sleet and freezing rain.
"So counter-intuitively, this area could see a reduction in snowfall totals but an increase in potential impacts due to very poor travel conditions as a result of the possible freezing rain," the weather service said.
Harris Teeter ran out of carts. RAN OUT OF CARTS. #snOMG#CLTwx
The North Carolina Zoo in Asheboro said it will be closed all weekend for the safety and welfare of its animals and guests alike."
At Burke Brothers Hardware in Raleigh, the state capital, frantic shoppers have "cleaned us out more or less so far," Jeff Hastings, an employee at the store, told NBC station WRAL.
Stuart Davis, who works at Briggs Hardware in Raleigh, agreed that the snow will be "good for business." All day Thursday, people have been calling "asking if we have sleds, ice melt and snow shovels," he told the station.
Meanwhile, in Clemson, South Carolina, the folks in charge of Clemson University's marching band were huddling Thursday to figure whether and how the band will make it to Tampa, Florida, for the Tigers' college football national championship game Monday against the University of Alabama.
The band is making the 575-mile journey in buses able to accommodate all of its instruments and equipment. It was scheduled to depart on Saturday.
"I want to be absolutely safe, doing the right thing," Mark Spede, director of the Tiger Band, told NBC station WYFF of Greenville. "So it's just a little bit of added stress that I wish I didn't have right now."