NEW YORK -- A powerful nor’easter is beginning to lash the mid-Atlantic and the Northeast, prompting flight cancellations, school closures and warnings from city and state officials to stay off roads.

The National Weather Service issued blizzard warnings for parts of Pennsylvania, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, New Hampshire and Maine.

The storm was expected to dump 1 to 2 feet of snow on the New York City metro area, with wind gusts of up to 55 mph. Forecasters said coastal areas could see sleet and rain mix in during the day, which would cut down on snow amounts.

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.

“A very strong winter storm could be life threatening for those who do not pay attention to safety precautions Tuesday morning,” the office said.

According to the airline-tracking website FlightAware, more than 5,000 Tuesday flights were canceled. Amtrak 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.

Forecasters said coastal areas could see sleet and rain mix in during the day, which would cut down on snow amounts.  

Federal workers in the Washington area were told they could report to work three hours late or take leave or work from home.

In Massachusetts, where forecasts called for 12 to 18 inches of snow, Gov. Charlie Baker encouraged motorists to stay off the roads and take public transit – and 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 closed Tuesday.Bank teller Jana White said her plans for riding out the storm included “lots of hot chocolate and a couple of sappy movies.” The 23-year-old Trenton, New Jersey, resident said she expected to get Tuesday off work.

“It’s a reminder that winter is always ready to take shot at you, so you have to stay prepared,” she said. “We’ve got food and snacks and drinks, so as long as the power stays on we should be in good shape.”

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 12 to 18 inches 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 afternoon, with snowfall rates as high as 2 to 4 inches per hour.

Pennsylvania Gov. Tom Wolf said approximately 700 National Guard members would be deployed, along with more than 2,000 snow plows to try to keep up with the storm, which 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 March 20.

Farther west, snowy weather conditions caused two crashes on a Chicago expressway that involved a total of 34 cars, Illinois State Police said.

A spokesman said seven people sustained minor injuries in Monday night’s pileup on the Kennedy Expressway. Both wrecks occurred in the express lanes of the highway on the city’s North Side.

Police say both crashes happened in the same area and the express lanes were closed for hours. Local lanes of the expressway remained open.And in Washington County, in southeast Wisconsin, sheriff’s deputies said snow-covered roads  and whiteout conditions contributed to a chain reaction pileup of some 30 vehicles -- many of them trucks -- on Interstate 41 Monday morning. Another 30 vehicles nearby wound up in a ditch or on the median. Southbound lanes were closed for six hours. Five people were taken to hospitals with what deputies described as non-life-threatening injuries.