(Reuters) – A powerful winter storm that hit the U.S. Southeast over the weekend knocked out power for more than 380,000 customers and forced the cancellation of hundreds of flights on Sunday.

Authorities urged residents to stay off the roads as snow, sleet, and freezing rain were expected to continue through Sunday night and into Monday morning, the National Weather Service said.

The agency reported between four and 12 inches (10 to 30 cm) of snow in some areas and warned about continuing snowfalls which could bring as much as a foot and a half (46 cm) from western and northern North Carolina to southwest Virginia.

More than 380,000 customers were without power in the Carolinas, Georgia, Alabama, Tennessee and Virginia on Sunday afternoon, Poweroutage.us reported.

The storm prompted more than 1,000 flight cancellations at Charlotte/Douglas International Airport, the sixth-busiest airport in the country, and other airports across the region, according to flight-tracking website FlightAware.

North Carolina Governor Roy Cooper said on Sunday that the state of emergency would remain in effect and that the North Carolina National Guard had been activated to help with the response.

The effects of the storm could last for days in the state, officials warned.

In North Raleigh, residents woke up to several inches of snow that blanketed roads, cars and homes. Many people took to Twitter to share photos of the unusually harsh weather, and the hashtag #Snowmageddon2018 was trending on Twitter on Sunday morning.

In South Carolina, snow gave way to sleet and rain as temperatures hovered around freezing, the South Carolina Emergency Management Division said on Twitter.

The storm formed earlier this week off the Texas coast and moved east, lashing parts of Arkansas and Tennessee with icy rain.