Virginia Department of Transportation employees shovel snow on a curve on Yellow Mountain Road off Route 220 in Roanoke, Va., on Sunday. (Stephanie Klein-Davis/Roanoke Times/AP)

A major winter storm unleashed its assault on the Southeast on Sunday, draping southern states with snow and ice as forecasters warned of treacherous travel conditions, flooding and power outages.

As snow fell from northeastern Georgia into central North Carolina, winter storm warnings stretched to portions of Tennessee, Kentucky and Virginia. The National Weather Service said significant snowfall accumulations are expected across the southern Appalachians and the adjacent Piedmont of North Carolina and south-central Virginia, with a foot of snow possible through Sunday night. By Sunday afternoon, some cities in North Carolina had received more than 14 inches of snow.

The governors of North Carolina and Virginia declared states of emergency and more than 1,700 flights were canceled Sunday across the United States. Nearly half a million people were reported without power in the Carolinas, Virginia, Tennessee, Alabama and Georgia. Duke Energy reported more than 240,000 outages in North Carolina and 170,000 in South Carolina on Sunday afternoon. In Virginia, Appalachian Power was reporting nearly 20,000 outages.

In York County, South Carolina, three men who were found unconscious and not breathing inside a home are believed to have died of carbon monoxide poisoning. NBC News reported that the York County Fire Marshal’s Office said the deaths were storm-related. Officials said they found a generator being worked on inside the home, according to the Associated Press.

North Carolina Gov. Roy Cooper urged residents to stay off the roads as the massive winter storm brought the state to standstill Sunday. Emergency crews, including the National Guard, had worked overnight to clear crashes on major interstates, Cooper said at a news conference Sunday. The North Carolina Highway Patrol responded to more than 500 crashes and 1,100 calls for service Sunday. One tractor-trailer ran off a road and into a river, Cooper said.

Officials said they were concerned about freezing rain in Charlotte and along the Interstate 85 corridor and in the southern mountains. Ice accumulation was creating hazardous driving conditions and increasing the potential for more power outages.

“Enjoy the beauty, but respect the danger,” Cooper said. “This storm is treacherous, especially if you try to drive in it. Travel conditions are extremely hazardous. Don’t put your life and the lives of first responders at risk by getting out on roads covered with snow and ice.”

The Washington region is expected to miss the worst of the snow, according to The Washington Post’s Capital Weather Gang, with forecasts predicting anywhere from a few flurries to snow showers closer to the metropolitan area. Some areas to the south, in Southern Maryland and toward Fredericksburg, Va., could see a few inches of snow.

Outside the metropolitan Washington area, forecasts are for ice and snow for the interior Southeast and into portions of the Mid-Atlantic states. Up to eight inches of snow is possible in central and southern Virginia, prompting Virginia Gov. Ralph Northam to declare a state of emergency Saturday.

“Travel will be severely affected across much of these areas, and some power outages are likely,” the National Weather Service said. “Mixed precipitation and wet snow to the south and east of the heaviest snowfall axis across the coastal plain of the Carolinas and southern Virginia will tend to lower overall accumulations there, but may still disrupt travel.”

This storm is likely to have a ma­jor im­pact on road­ways, as well as air and rail trav­el through the start of the workweek.

As of Sunday afternoon, airports in the storm’s path were experiencing reduced operations, while south of Washington, intercity rail riders faced disruptions in service, which are expected to continue through Tuesday.

Am­trak canceled serv­ice to areas south of Washington start­ing Saturday and continuing through Tuesday. Some North­east Regional trains are op­er­ating only north of Washington. The chan­ges affect Auto Train, Silver Me­te­or, Crescent, Car­o­lin­ian, Pied­mont and Silver Star trains, among others. (See Amtrak’s full list below.)

“For the safety of our customers and employees, the operating plan for service will be adjusted,” Amtrak said in an announcement.

Am­trak is also waiv­ing fees for travelers and said it will ac­com­mo­date cus­tom­ers on oth­er trains. Airlines, in­clud­ing American and Delta, said travelers can change their flights with­out pen­al­ties for trav­el to and from the re­gion for trips Sunday and Monday. The severe weather is affecting airports in North Carolina, South Carolina, Tennessee and Virginia.

By Sunday afternoon, reported that more than 1,650 Sunday flights had been canceled nationwide, with many of the disruptions in North Carolina. However, that number is expected to rise Sunday afternoon and Monday, with the potential for hundreds of flights to be canceled. Nearly 400 flights Monday were preemptively canceled.

Charlotte Douglas International Airport, the sixth-busiest airport in the country, is experiencing most of the disruption. Nearly 600 flights from the airport had been canceled Sunday, and as many headed to Charlotte also were canceled. The airport said early Sunday it was open and operational, and crews continued to clear the airfield, airport roadways, overpasses and parking lots.

“Travelers are encouraged to frequently check with their air carrier for any cancellations or delays before coming to the Airport,” the airport said.

American Airlines said it reduced operations at its Charlotte hub starting Saturday evening. Scattered cancellations are expected through Monday morning, the airline said. Delta said the storm is expected to affect operations at seven hubs across the region.

At Richmond International Airport, nearly 100 cancellations were reported Sunday. The airport was urging travelers to check their flight statuses before heading to the airport as the number of flights canceled is expected to continue Monday.

The immediate Washington region was not expecting major impacts from the storm. As of Sunday morning, the snowfall was sticking to the south and had yet to make it to Fredericksburg. The bulk of accumulating snow was expected to remain south of the immediate metro area, according to the Capital Weather Gang. But flurries and a dusting inside the Beltway were still possible.

Capital Weather Gang's snowfall forecast for Sunday.

Transportation officials in Maryland and Virginia said they were closely monitoring the conditions Sunday. Maryland’s State Highway Administration said it had crews ready for a chance of wintry weather developing in southern Maryland and the lower Eastern Shore.

In Virginia, crews were treating roads Sunday in Southside, Southwest and Central Virginia, while officials said crews are ready to treat roads in Northern Virginia if the storm makes a shift north.

Transportation officials in areas of North Carolina, Tennessee and Virginia that were experiencing significant snowfall were urging residents to stay off the roads. The North Carolina Emergency Management office said crews were clearing roads and reported more than 140,600 homes without power Sunday morning.

In Virginia, state police responded to more than 140 crashes and dozens of calls for disabled vehicles across western, southern and central Virginia regions affected by the storm. State Police said the snow was coming down faster than the state crews could keep up with midday Sunday and that Interstate 81 in Washington County became impassable. Several tractor-trailers slid off the highway and other vehicles became stuck, police said.

“Please stay off the road and delay your travel until the highways are clear,” Virginia State Police spokeswoman Corinne Geller said.