BOSTON — A storm poised to dump up to 3 feet of snow from New York City to Boston and beyond beginning Friday could be one for the record books, forecasters warned, as residents scurried to stock up on food and water and road crews readied salt and sand.

Before the first snowflake had fallen, Boston, Providence, R.I., Hartford, Conn., and other towns and cities in New England and upstate New York towns canceled school Friday, and airlines scratched more than 3,700 flights through Saturday, with the disruptions from the blizzard certain to ripple across the U.S.

“This one doesn’t come along every day. This is going to be a dangerous winter storm,” said Alan Dunham, meteorologist for the National Weather Service in Taunton, Mass. “Wherever you need to get to, get there by Friday afternoon and don’t plan on leaving.”

The snow began falling Friday morning in some areas, with the heaviest amounts falling at night and into Saturday. Wind gusts could reach 75 mph. Widespread power failures were feared, along with flooding in coastal areas still recovering from Superstorm Sandy in October.

Boston could get up to 3 feet of snow, while New York City was expecting 10 to 12 inches. Mayor Michael Bloomberg said plows and 250,000 tons of salt were being put on standby. To the south, Philadelphia was looking at a possible 2 to 5 inches.

“We hope forecasts are exaggerating the amount of snow, but you never can tell,” Bloomberg said, adding that at least the bad weather is arriving on a weekend, when the traffic is lighter and snowplows can clean up the streets more easily.

Amtrak said its Northeast trains will stop running Friday afternoon. The organizers of New York’s Fashion Week — a closely watched series of fashion shows held under a big tent — said they will have extra crews to help with snow removal and will turn up the heat and add an extra layer to the venue.

Airlines have cancelled 3,775 flights in preparation for the Northeast storm, according to airline tracking website FlightAware. At New York City’s three main airports, most domestic carriers planned to cease operations between 2 p.m. and 5 p.m. Friday, resuming after noon on Saturday, FlightAware said. At Boston’s Logan and other New England airports, most airlines were to cease operations between noon and 4 p.m., and would restart Saturday afternoon.

Blizzard warnings were posted for parts of New Jersey and New York’s Long Island, as well as portions of Massachusetts, Rhode Island and Connecticut, including Hartford, New Haven, Conn., and Providence. The warnings extended into New Hampshire and Maine.

In New England, it could prove to be among the top 10 snowstorms in history, and perhaps even break Boston’s record of 27.6 inches, set in 2003, forecasters said. The last major snowfall in southern New England was well over a year ago — the Halloween storm of 2011.

Dunham said southern New England has seen less than half its normal snowfall this season, but “we’re going to catch up in a heck of a hurry.” He added: “Everybody’s going to get plastered with snow.”

Diane Lopes was among the shoppers who packed a supermarket Thursday in the coastal fishing city of Gloucester, Mass. She said she went to a different grocery earlier in the day but it was too crowded. Lopes said she has strep throat and normally wouldn’t leave the house but had to stock up on basic foods — “and lots of wine.”

She chuckled at the excitement the storm was creating in a place where snow is routine.

“Why are us New Englanders so crazy, right?” she said.

At a Shaw’s supermarket in Belmont, Mass., Susan Lichtenstein stocked up, with memories of a 1978 blizzard on her mind. “This is panic shopping, so bread, milk, a snow shovel in case our snow shovel breaks,” she said.

In New Hampshire, Dartmouth College student Evan Diamond and other members of the ski team were getting ready for races at the Ivy League school’s winter carnival.

“We’re pretty excited about it because this has been an unusual winter for us,” he said. “We’ve been going back and forth between having really solid cold snaps and then the rain washing everything away.”

But he said the snow might be too much of a good thing this weekend: “For skiing, we like to have a nice hard surface, so it will be kind of tough to get the hill ready.”

The governors of Connecticut and Massachusetts ordered nonessential state workers to stay home Friday and urged travelers to stay home.

Terrance Rodriguez, a doorman at a luxury apartment complex in Boston, took the forecast in stride.

“It’s just another day in Boston. It’s to be expected. We’re in a town where it’s going to snow,” he said. “It’s like doomsday prep. It doesn’t need to be. People just take it to the extreme.”