TAMPA - A powerful nor'easter pounded the mid-Atlantic and the Northeast early Tuesday, prompting flight cancellations nationwide.
The National Weather Service issued blizzard warnings for parts of Pennsylvania, New Jersey, New York,
According to the airline-tracking website FlightAware, more than 5,000 flights Tuesday were canceled, including at least 139 flights out of Tampa International Airport.
Some travelers hoping to get to New York were told the soonest they could get a flight was next weekend.
More than 2,800 flights were canceled in the New York City area, where about 200 passengers were stranded at John F. Kennedy airport. Amtrak also canceled and modified service up and down the Northeast Corridor. In New York City, the above-ground portions of the subway system were being shut down Tuesday morning.
In the nation's capital, the U.S. Office of Personnel Management announced a three-hour delayed arrival for non-emergency employees at area federal offices - with an option of unscheduled leave or telework. Emergency employees of the federal government in the Washington, D.C., area were to report on time unless otherwise directed.
The National Weather Service issued blizzard warnings for parts of Pennsylvania, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, Maine and Vermont.
The storm was expected to dump 12 to 18 inches of snow on the New York City metro area with wind gusts of up to 55 mph.
The weather service's office near Philadelphia called the storm "life-threatening" and warned people to "shelter in place." Coastal flood warnings were in effect from Massachusetts to Delaware.
In Massachusetts, where forecasts called for 12 to 18 inches of snow, Gov. Charlie Baker encouraged motorists to stay off the roads and to take public transit only if absolutely necessary. The fast snowfall rates will "create hazardous driving conditions across the Commonwealth," he said.
Schools in New York City, Philadelphia, Boston and elsewhere were all closed Tuesday.
In Maryland, Gov. Larry Hogan declared a state of emergency and urged residents not to be lulled into a false sense of security due to the mild winter.
"This is a serious winter storm," Hogan said, adding that some parts of the state could see over a foot of snow. "It's obviously going to be the biggest event we've had this season and people need to be prepared. They need to be safe."
The heaviest snowfall was expected Tuesday morning through the afternoon, with snowfall rates as high as 2 to 4 inches per hour.
Pennsylvania Gov. Tom Wolf said that approximately 700 National Guard members would be deployed, along with more than 2,000 snow plows to keep up with the storm that was expected to bring a foot or more of snow to some parts of the state.
The nor'easter comes a week after the region saw temperatures climb into the 60s. Spring officially starts on March 20.
The snow threat in the Northeast also was causing college basketball teams to alter their travel plans as the fierce storm bore down on the region.
"We are closely tracking the weather and working with our travel partners and teams in the tournament to ensure the safety of our student-athletes, coaches, administrators, officials and fans," the NCAA said in a statement.
The Associated Press contributed to this report.