Freezing winter conditions are bringing a post-Christmas storm to the East Coast, causing chaos for holiday travelers.
As the snow was piling up from the Carolinas to New England, Amtrak shut down train service between New York and Boston, and and all flights at airports up and down the East Coast were canceled.
More than a foot of snow is forecast for New York City and New England, and nearly two dozen states east of the Mississippi are under severe weather warnings.
Airlines have grounded hundreds of flights traveling in and out of East Coast airports, including 1,400 cancellations at New York City-area airports, and they have said more cancellations were likely as the storm progressed.
Travel chaos already affected the south, where in Atlanta the first white Christmas since 1882 brought 1.2 inches. Dozens of car crashes were reported across the south, according The Associated Press.
Preparations began across the mid-Atlantic region with Washington transportation officials pretreated roads and readied 200 salt trucks, plows and other pieces of equipment. Baltimore and Washington are expected to get about six inches.
But it's the northeast that is being hit the hardest, with forecasters issuing a blizzard warning for New York City for Sunday and Monday. Eleven to 16 inches of snow is expected, along with strong winds that will reduce visibility to near zero.
New York mayor Michael Bloomberg held a press conference on Sunday afternoon, updating residents on the city's plan of action, and advising them to stay off the roads.
"If you have to go out today, please leave the cars at home," Bloomberg said, "take mass transit and be careful."
Philadelphia is under a Code Blue Alert for severe weather, according to the city's official website, while the city of Boston has declared a snow emergency and the Rhode Island Emergency Management Agency has advised residents to stay off highways, calling driving conditions "near impossible."
Rhode Island and most of eastern Massachusetts, including Boston, have also been issued a blizzard warning, with 15 to 20 inches of snow expected. A blizzard warning is issued when snow is accompanied by sustained winds or gusts over 35 mph.
Amtrak spokesman Cliff Cole said all trains between Boston and New York will be canceled as of 5 p.m. today, as has service between Portland, Maine and Boston.
"Blizzard like conditions associated with a major winter storm continues to impact a large portion of east coast," Cole said in a statement. "This has caused Amtrak to make several service adjustments including the cancellation Northeast Corridor service between Boston and New York beginning later this afternoon."
"This is going to be a real honest to goodness nor'easter and a blizzard," Dr. Joe Sobel of AccuWeather.com said. "Air travel I think is going to be shut down as we go through Sunday, especially midday Sunday from Washington to New York."
By early Sunday, Maryland, Virginia and North Carolina declared states of emergency. Amtrak canceled several of its trains in Virginia.
In North Carolina, five inches of snow piled up in Raleigh, while Asheville broke its Christmas record with 6 and a half inches, including another two and a half today.
Most major airlines were cancelling flights scheduled to head into the storm's path as of early this morning.
Continental Airlines released a statement saying, "We have pre-cancelled about two hundred and fifty flights and we are continuing to monitor the storm's progress and its full potential impact on our operations."
Travel Chaos in the Air and on the Roads
United Airlines canceled dozens of Sunday departures from Newark, Philadelphia, New York's LaGuardia and JFK, Boston and other airports. In the New York area alone, a total of 1000 flights have been cancelled.
AirTran and Southwest Airlines also canceled flights, mostly in or out of Washington Dulles, Baltimore and Newark.
Delta Air Lines spokesman Kent Landers said the airline proactively canceled about 850 mainline and regional flights system wide today because of the weather.
"Most cancelations are concentrated from the Carolinas through New York," he said.
Stranded passengers can take solace in the fact that most airlines are waiving fees for one-time changes in affected areas. Passengers are being encouraged to make travel changes via the carrier's websites.
Those planning on hitting the roads to return home after holiday travel -- an estimated one in 10 travelers -- are advised not to until well after the storm has passed.
"If you can avoid being on the road, then don't travel, if you are flying, then try to book the next flight out roads," said John Townsend, Manager, Public Affairs at the American Ambulance Association (AAA).
With whiteout blizzard conditions predicted up and down the eastern seaboard, road conditions are unsafe. Plows are already out salting the roads and residents are doing what they can to prepare.
"It's going to be not only the airports, but the entire East Coast is going to be a problem along I-95. That's the main thoroughfare the folks use to travel the East Coast," ABC News' David Kerley said.
"They are expecting whiteout conditions. This is a true nor'easter," he said.
Authorities and meteorologists are encouraging people to stay indoors and not to brave the storm unless there is no other choice.
"Stay inside if you can. Don't travel if it's not absolutely necessary, and be careful," National Weather Service meteorologist Kyle Struckmann said.
"The heaviest snow will be late this afternoon and this evening, probably before midnight, then it will start a general trend of improvement, but it will still be snowing most of the night," Struckmann said.
And sports fans staying at home to wait out the weather may be disappointed, too. Today's Philadelphia Eagles-Minnesota Vikings game has been postponed until Tuesday night.
This follows the Vikings stadium roof collapse three weeks ago, and the game they were forced to play last week during a snowstorm at an outdoor college stadium.
The Associated Press contributed to this report