Overnight, a layer of snow coated roads and rooftops, front stoops and back gardens like thick cake icing. Six to 10 inches of snow were expected to fall on New York City and eight to 12 inches on Long Island.
The snow was forecast to stop around 9 a.m. Winds gusting between 30 and 45 miles an hour in some areas were expected to compound the misery, blowing newly plowed snow back into roadways and driving wind chill temperatures to as low as minus 20 degrees in some areas, according to the National Weather Service.
The storm promised to be the first test of New York City’s new mayor, Bill de Blasio. In his last job, as the city’s public advocate, Mr. de Blasio was critical of the response under his predecessor, Michael R. Bloomberg, when plows were slow to reach some neighborhoods, particularly in the boroughs outside Manhattan, after a storm in 2010.
On Friday morning, Mr. De Blasio sent a photo via Twitter of him shoveling snow in Park Slope, Brooklyn.
“This has been and remains a dangerous storm,” he said in the statement. “It is going to be bitter cold today, and New Yorkers need to be extremely careful going outdoors. The best things people can do are to stay off the roads so we can clear them as fast as possible, and to check in on elderly and vulnerable neighbors who might need help this morning.”
Through the night, a fleet of snowplows patrolled the city streets, and workers in face masks and heavy parkas shoveled the sidewalks. Officials said 450 salt spreaders had been out since early Thursday morning and 2,500 trucks had been outfitted with plows.
John J. Doherty, the sanitation commissioner, said Friday morning that the snowplows had “been through most of the streets at least once if not two or three times.”
The city announced that public schools would be closed. Flight operations at John F. Kennedy Airport were suspended because of poor visibility, the Port Authority of New York and New Jersey said. The terminals remained open. As of 6:30 a.m., the airport reported 120 flight cancellations. La Guardia Airport and Newark Liberty International Airport remained open but reported 190 and 274 cancellations, respectively, by 6:30 a.m.
Subways were running Friday morning, although because cars had been stored underground on express tracks, trains were running local lines for the start of the morning rush. The Metropolitan Transportation Authority said bus passengers could also expect delays because of road conditions. The Department of Buses installed tire chains on all buses operating on Friday morning, the authority said. The system was expected to run at about 85 percent capacity.
The authority’s railroads, Metro-North Railroad and Long Island Rail Road, were operating on weekend schedules. On the Long Island Rail Road, there was no service between Greenport and Ronkonkoma; a bus connection was being provided.
All of the authority’s bridges and tunnels remained open, though drivers are being asked to travel at reduced speeds.
The Port Authority added that PATH trains were running on a normal schedule.
Gov. Andrew M. Cuomo of New York declared a state of emergency and ordered several major highways, including the Long Island Expressway and the New York State Thruway south of Albany, shut down from midnight to 5 a.m.
Other state officials said drivers who ventured onto roads that had been ordered closed could face a misdemeanor charge.
The storm was a classic nor’easter, a volatile brew of cold air from the Midwest and Canada that collided with warmer, moist air that had been circulating on the East Coast. It left a trail of traffic accidents across Michigan and Ohio and stranded thousands of airline passengers before the weekend crush of holiday travelers heading home.