A powerful winter storm bearing down on the Northeast forced thousands of flight cancelations Thursday, snarling travel plans for fliers across the country and dumping more than a foot of snow in some areas, according to estimates.

VIDEO: MILLIONS BRACE FOR BLAST OF WINTER WEATHER

The airlines canceled more than 3,500 flights Wednesday through Friday. A ground stop at New York's JFK airport lengthened the delays before it was lifted Thursday afternoon.

In addition, emergency officials warned of high winds, coastal flooding and possible power outages from New England down to Pennsylvania and New Jersey.

The storm reportedly killed at least one person. A doorman slipped and crashed through a glass window while shoveling snow on New York City's Upper East Side, cutting him severely, police sources told The New York Post.

LOUISIANA IN RECOVERY MODE AFTER POWERFUL LINE OF TORNADOES

Up to 11 inches fell in New York's Hudson Valley by noon, while areas around New York City and Long Island received 6 to 9 inches, according to the National Weather Service. West Hartford, Connecticut, had more than 13 inches, and Ludlow, Massachusetts, 16 1/2.

A blizzard warning was posted for a swath of the New England coast, with forecasters saying Boston and Providence, Rhode Island, could get up to a foot and a half by the evening.

Farther north, Manchester, New Hampshire, had received at least 11 inches by midafternoon and Berwick, Maine, about a foot.

"We were waiting for a good one all year," said Morgan Crum, a manager at Katz Ace Hardware in Glastonbury, Connecticut, where more than 50 people stopped in to buy shovels, ice melt, gas cans and other storm provisions. "We live in New England. This is what we expect."

New York City Mayor Bill de Blasio said people should stay home. "If you need to go out, please, don't use your car," de Blasio said on NY1 television.

Several school systems canceled Thursday classes -- including New York City, Philadelphia and Boston.

“Don’t be surprised if some people start reporting rumbles of thunder, as the system is strengthening,” Brian Edwards, meteorologist with AccuWeather, told The New York Post. “Thundersnow happens when the cold air is rising very rapidly. It tends to take place on these rare occasions, when you have these big snow rates.”

Commuters in the densely populated region faced windblown snow -- less than 24 hours after enjoying spring-like temperatures -- and faced slick highways.

Massachusetts activated its emergency management bunker in Framingham, where Gov. Charlie Baker was scheduled to provide updates on the storm at midday. Baker urged people to stay off the roads to allow plows and sanders to do their work.

State offices in New Jersey were closed, as were the courts in Massachusetts. Government offices in the Delaware, Bucks, Chester and Montgomery counties surrounding Philadelphia also were shuttered.

The Associated Press contributed to this report.