NEW YORK (AP) – Cities across the Northeast mobilized snowploughs and airlines cancelled thousands of flights Monday as a potentially historic storm pushed its way up the Philadelphia-to-Boston corridor with what forecasters said could be up to 2 feet of snow.

More than 4,000 flights were cancelled or delayed, schools planned to close early and a hospital in New York increased staff and outfitted its vehicles with snow travelling gear.

The National Weather Service said the nor’easter would bring heavy snow, powerful winds and widespread coastal flooding starting Monday and through Tuesday. A blizzard warning was issued for a 250-mile stretch of the Northeast, including New York and Boston.

A tractor-trailer jack-knifed, and a truck hauling beer crashed into the median on a section of Interstate 81 near Harrisburg, Pennsylvania, during the Monday morning commute, forcing officials to shut down the southbound lanes. No injuries were reported.

Some schools were planning to close early or not open at all Monday in Pennsylvania, New Jersey, New York and Connecticut.

“This could be a storm the likes of which we have never seen before,” New York City Mayor Bill de Blasio said at a Sunday news conference in a Manhattan sanitation garage where workers were preparing ploughs and salt for the massive cleanup on about 6,000 miles of city roadways.

Connecticut Governor Dannel P Malloy ordered a travel ban on Connecticut highways, while officials in other states asked residents to avoid any unnecessary travel.

The Nassau University Medical Center on Long Island increased staff and outfitted vehicles with snow travelling gear. Hospital officials said they expect a large increase in patients as doctors’ offices and clinics close due to the weather.

In Massachusetts, Governor Charlie Baker warned residents to prepare for roads that are “very hard, if not impossible, to navigate,” power outages and possibly even a lack of public transportation.

Boston’s Logan International Airport said there would be no flights after 7:00 pm Monday, and did not expect to resume flights until late Wednesday.

Boston is expected to get 18 to 24 inches of snow, with up to 2 feet or more west of the city, and Philadelphia could see up to a foot, the weather service said.

The Washington area expected only a couple of inches, with steadily increasing amounts as the storm heads north.

“We do anticipate very heavy snowfall totals,” said Bob Oravec, lead forecaster with the weather service in College Park, Maryland. “In addition to heavy snow, with blizzard warnings, there’s a big threat of high, damaging winds, and that will be increasing Monday into Tuesday. A lot of blowing, drifting and such.”

President Barack Obama, who is travelling in India, has been briefed on the storm, spokesman Josh Earnest said Monday. White House officials also have been in touch with officials from states “up and down the Eastern seaboard” that are in the storm’s path, Earnest said.

Wind gusts of 75 mph or more are possible for coastal areas of Massachusetts, and up to 50 mph further inland, Oravec said.

A storm system driving out of the Midwest brought several inches of snow to Ohio on Sunday. A new low pressure system was expected to form off the Carolina coast and ultimately spread from the nation’s capital to Maine for a “crippling and potentially historic blizzard,” the weather service said.

New York Governor Andrew Cuomo urged commuters to stay home on Monday and warned that mass transit and roadways could be closed before the evening rush hour, even major highways such as the New York Thruway, Interstate 84 and the Long Island Expressway.

In New York City, the Greater New York Taxi Association offered free cab service for emergency responders trying to get to work, and disabled and elderly residents who become stranded.

The New York Rangers decided to practice Monday afternoon at the Islanders’ home arena on Long Island instead of at their own training facility just outside New York City. They’ll stay overnight on Long Island for Tuesday’s game against their rival — if it’s still held.

The Super Bowl-bound New England Patriots expected to be out of town by the time the storm arrives in Boston. The team plans to leave Logan Airport at 12:30 pm Monday for Phoenix, where the temperature will reach the high 60s.