Government offices closed early and public transportation ground to a near halt in the US capital, where snow began accumulating Friday in what could be one of the worst blizzards to hit Washington in years.
The National Weather Service posted a blizzard warning for an area that stretched from Virginia in the south to New York in the north, including Washington, Baltimore, Philadelphia and New York City. Winter storm warnings were in place beyond the blizzard zone, taking in much of the eastern part of the country.
Heavy snow and strong winds could "produce life-threatening blizzard conditions across portions of the Mid-Atlantic Friday night and Saturday," the weather service said.
Snowfall of up to 30 centimeters had already fallen in parts of North Carolina and measurable snow had fallen in 11 states across the south, the weather service said.
Washington Mayor Muriel Bowser told residents to get off the streets and stay home.
States of emergency have been declared in Washington and the neighbouring states of Virginia and Maryland as well as several other states. Authorities warned that snow would continue to fall for most of the day Saturday, producing life-threatening weather conditions.
"Areas from Baltimore and Washington, DC, to near Philadelphia can expect an all-out blizzard with snowfall averaging 12-24 inches [30-60 centimetres]," Accuweather said, adding that as much as 7 centimetres per hour could fall overnight Friday.
The Federal Emergency Management Agency and Homeland Security Secretary Jeh Johnson were "closely monitoring the snow storm that is hitting the East Coast and the mid-Atlantic region in particular, and are prepared to assist local officials as needed," he said.
The federal government closed its offices at 12 pm (1700 GMT), and Washington's bus service was suspended five hours later. The city's subway system was scheduled to stop running at 11 pm (0400 GMT Saturday) and remain shut down for two days.
The storm is expected to affect some 85 million people in 19 states. Thousands of flights had been cancelled along the east coast, according to the flight tracking website flightaware.com.
Residents had plenty of warning before snow began falling in Washington at around 1 pm (1800 GMT). Schools were shuttered in advance of the storm. Grocers' shelves were stripped bare as residents stocked up on essentials and snow supplies to weather the storm.
The National Weather Service said that accumulations of 30 to 60 centimetres of snow were possible across a wide swath of the eastern US from Kentucky to New Jersey with more than 60 centimetres possible in the Washington and Baltimore metropolitan region.
The forecast also warned of strong winds, heavy ice further south and possible coastal flooding.
"The wind is what's worrying us. It's a very humbling forecast," said Robert Maloney, an emergency response team official in the mayor's office in Baltimore. "We are going to have people without power for a long time."
North Carolina already experienced traffic chaos on Friday morning. The storm produced rain there, and it froze when it hit the streets.
Power companies said outages were possible as heavy snow and high winds could damage power lines.
Pepco, which provides power in Washington and its Maryland suburbs, said it had brought on extra staff but efforts to restore power could be slowed by hazardous weather conditions.
"Pepco is well prepared for the storm, but if roads become impassable due to deep snow and downed trees, our power restoration efforts could be slowed," Pepco president Donna Cooper said.
"Customers need to plan for emergencies, and now is the time to do so. Our restoration efforts could take multiple days," she said.