The city was expected to receive up to five inches of snow, part of the second winter storm to hit the East Coast this week.A winter storm blew across the Northeast overnight on Friday, dropping the first significant snowfall of the winter on New York City and creating treacherous conditions for the morning commute.Snow fell heavily in the pre-dawn hours in the New York region and parts of New England, causing flight delays and cancellations at airports and slowing traffic and train service. New York City’s schools remained open, but the storm prompted school closings and delays across the region.Elected officials urged commuters to stay off the roads and work from home if they could. The Metropolitan Transportation Authority, which operates the New York subway, said its crews were working to keep trains and buses running.“If you must travel, use extra caution, plan extra time and check service status before you go,” the authority advised Friday morning.The Metro-North Railroad, which is operated by the authority and serves suburbs north of the city, was operating on a Saturday schedule because of the storm.Winter Storms in the United StatesFrom the East Coast to the Western U.S., a barrage of winter storms has wreaked havoc across the country.Virginia: Hundreds of drivers were stranded for more than 24 hours after a snowstorm brought I-95 to a standstill near Washington, D.C.Colorado: Days after a catastrophic fire destroyed hundreds of homes near Boulder, residents were hit with nearly a foot of snow.Widespread Power Outages: More than half a million customers were left without power in the Southeast and Mid-Atlantic.Travel Disruptions: Covid-related staff shortages and the storms have led to thousands of flight cancellations.The National Weather Service issued a winter weather advisory through noon for the New York region, warning that roads would be slippery and urging drivers to be cautious. New York City could see up to five inches of snow, and up to seven inches could fall on Long Island.In New Jersey, Gov. Phil Murphy declared a state of emergency that began at 10 p.m. Thursday. “If you can work remotely tomorrow or report later than usual, you may wish to take those options and stay off the roads,” Mr. Murphy said at a news conference Thursday evening.Snowplows were clearing the streets of New York City for the first time this winter, according to a spokesman for Eric Adams, the city’s new mayor. The city was spared by a storm earlier in the week that dumped up to a foot of snow on parts of the Mid-Atlantic States, including Atlantic City and other areas along the New Jersey shore.The storm presented an early challenge for Mr. Adams, who was sworn in on New Year’s Eve. He conferred with his emergency management team at 4 a.m., the spokesman said.Airlines canceled hundreds of flights at the three major airports that serve New York City, but it was not clear how many of those cancellations resulted from the storm. In recent weeks, airlines have canceled thousands of flights across the country because of inadequate staffing caused in part by the rapid spread of the Omicron variant of the coronavirus.In New England, winter storm warnings were issued for most of eastern Massachusetts and nearly all of Rhode Island. Farther north, a portion of Maine was under a blizzard warning.The Washington area, slammed just days ago with more than eight inches of snow, was expected to get another round, with the Weather Service forecasting up to four inches. Federal offices in Washington would be closed on Friday, officials said.A man walked his dog by the Ohio River during a snow storm in Louisville, Ky., on Thursday.Amira Karaoud/ReutersSome school districts along the Interstate-95 corridor, already facing growing concerns amid rising Covid-19 cases, adjusted their operations for Friday. Mayor Muriel Bowser of Washington announced that schools would be closed because of the storm. Public schools in Philadelphia were shifting to remote learning, while several districts in New Jersey were either closing for the day or were operating on a delay.The new storm system comes on the heels of a wintry wallop that coated roads with snow and ice, set new daily snowfall records, knocked out power for half a million people, jammed roads for miles and stranded drivers overnight in their cars along Interstate 95 south of Washington.The snowy weather comes as the United States — from Montana to Colorado to Kentucky to Massachusetts — is facing a shortage of snow plow drivers, which has complicated removal efforts.Officials have blamed the shortage partly on broader labor conditions; truck drivers have been in demand for years, and the industrywide shortage has reached record highs in recent months. A surge in the Omicron variant has worsened the situation, forcing some snow plow drivers to call out sick.Some areas are going to great lengths to attract drivers. Watertown, Mass., is paying $200 per hour to drivers with a commercial license, with rates increasing as high as $310 if they have specialized equipment, The Boston Globe reported in November.A car fell off the road on Interstate 40, which had a heavy traffic jam due to snow and accidents in Lebanon, Tenn., on Thursday.Caitlin Jones, via ReutersDaniel Victor