Massive winter storm sweeps across US

More than 400,000 customers in the US as far west as Texas were without power and more than 9,600 flights were expected to be cancelled on Sunday ahead of a monster winter storm that threatened to paralyse eastern states with heavy snowfall.

Forecasters said snow, sleet and freezing rain, accompanied by dangerously frigid temperatures, would sweep the eastern two-thirds of the nation on Sunday and into next week.

Calling the storms "historic," President Donald Trump on Saturday approved federal emergency disaster declarations in South Carolina, Virginia, Tennessee, Georgia, North Carolina, Maryland, Arkansas, Kentucky, Louisiana, Mississippi, Indiana, and West Virginia.

"We will continue to monitor, and stay in touch with all States in the path of this storm. Stay Safe, and Stay Warm," Trump wrote in a post on Truth Social.

Seventeen states and the District of Columbia have declared weather emergencies, the Department of Homeland Security said.

"We do have tens of thousands of people in affected states in the South that have lost power. We have utility crews that are working to restore that as quick as possible," DHS Secretary Kristi Noem said late Saturday afternoon.

The number of outages continued to rise. As of 6:30 a.m. EST (1130 GMT) on Sunday, more than 400,000 US customers were without electricity, according to PowerOutage.us, with 100,000 each in Mississippi and Texas. Other states affected included Louisiana, Tennessee and New Mexico.

The Department of Energy on Saturday issued an emergency order authorizing the Electric Reliability Council of Texas to deploy backup generation resources at data centers and other major facilities, aiming to limit blackouts in the state.

On Sunday, the DOE issued an emergency order to authorise grid operator PJM Interconnection to run "specified resources" in the mid-Atlantic region, regardless of limits due to state laws or environmental permits..

The US National Weather Service warned of an unusually expansive and long-duration winter storm that will bring widespread, heavy ice accumulation in the southeast US, where "crippling to locally catastrophic impacts" can be expected.

Weather service forecasters predicted record cold temperatures and dangerously cold wind chills descending further into the Great Plains region of the US by Monday.

More than 9,600 US flights scheduled for Sunday were cancelled, according to flight tracking website FlightAware, with over 4,000 flights cancelled on Saturday. 

Major US airlines warned passengers to stay alert for abrupt flight changes and cancellations.

In an update on Saturday morning, Delta Air Lines said it was continuing to make schedule adjustments, with additional cancellations in the morning for Atlanta and along the East Coast, including in Boston and New York City.

It added it was relocating experts from cold-weather hubs to support de-icing and baggage teams at several southern airports.

JetBlue said that as of Saturday morning it had canceled about 1,000 flights through Monday, with additional cancellations possible.

United Airlines said in an email that its weather preparations included proactively canceling some flights in places with the worst weather.

US electric grid operators on Saturday stepped up precautions to avoid rotating blackouts.

Dominion Energy, whose Virginia operations include the largest collection of data centers in the world, said if its ice forecast holds, it could be among the largest-ever winter events to affect the utility's operations.

Noem, speaking at a news conference about US government preparations for the storm, warned Americans to take precautions.

"It’s going to be very, very cold," Noem said. "So we'd encourage everybody to stock up on fuel, stock up on food, and we will get through this together."