Updated

major winter storm slamming the Northeast Monday is forecast to drop up to two feet of snow across an area stretching from Pennsylvania to New England, impacting cities such as Philadelphia, New York City and Boston. 

Officials along the heavily populated I-95 corridor are warning residents to stay off the roads as snowfall rates may exceed 2 inches an hour in some parts, while dozens of winter weather warnings and advisories are in effect. Nearly all flights heading in and out of New York City airports also have been canceled, statistics show

"A powerful Nor'easter and winter storm will pound much of the Northeast and New England today and Tuesday with a variety of hazards," the National Weather Service says. "Widespread heavy snow, gusty winds, near blizzard conditions and coastal impacts are very likely."

A pedestrian walks down a snow covered street in the Brooklyn borough of New York City on Monday. (AP)

A pedestrian walks down a snow covered street in the Brooklyn borough of New York City on Monday. (AP)

The NWS adds that "on Monday evening, the snow will expand into Northern New England and continue over parts of the Northeast into Wednesday" and that rain and freezing rain is possible today from Washington, D.C., to Philadelphia. 

WINTER STORM BRINGING HEAVY SNOW, STRONG WINDS TO THE NORTHEAST 

The NWS is forecasting that northeast Pennsylvania, northern New Jersey and southern New York will see the heaviest snowfall, with New York City expected to get as much as 20 inches. 

At least 6 inches of snow had fallen in the Pittsburgh area by early Monday, while Philadelphia had about 2 inches of sleet and snow. In New York City -- where Mayor Bill de Blasio has restricted nonessential travel and warned locals of wind gusts of up to 50 miles per hour - 8 inches has already fallen in some parts.

"At the most intense points, you are going to see two to four inches of snow per hour," he said Monday.

"Travel will be very difficult to impossible," the NWS says. "The hazardous conditions will impact the morning and evening commute. Gusty winds could bring down tree branches." 

New York State Police reported that a tractor-trailer overturned on the Gov. Mario M. Cuomo Bridge in Rockland County early Monday morning as a result of the worsening conditions. Police also reported other trucks skidding off Interstate-84 in Orange County.

Elsewhere, Philadelphia is expected to get 11 inches of snow through Tuesday night -- an increase from the 5 total inches that forecasters previously were predicting as of this morning. Boston is also forecast to receive 11 inches of snow over the same period. 

Arturo Diaz, 4, enjoys playing in a deep snow bank in Hoboken, N.J., on Monday. (AP)

Arturo Diaz, 4, enjoys playing in a deep snow bank in Hoboken, N.J., on Monday. (AP)

Much of Connecticut, Rhode Island, Massachusetts, Vermont, New Hampshire and Maine will get at least 6 inches of snow. Isolated parts of Pennsylvania and New Jersey, however, could get more than 2 feet. 

Winds are also forecast to cause coastal flooding from the Mid-Atlantic to New England into Tuesday. 

A pedestrian crosses a road in Tarrytown, N.Y. as a nor'easter is blanketing much of New York state on on Monday. Up to two feet of snow is predicted before the storm moves out Tuesday evening. (Reuters)

A pedestrian crosses a road in Tarrytown, N.Y. as a nor'easter is blanketing much of New York state on on Monday. Up to two feet of snow is predicted before the storm moves out Tuesday evening. (Reuters)

The storm made its way across the Midwest over the weekend before turning up along the Mid-Atlantic towards New England, bringing over a foot of snow in some parts of the country.

Lara Pagano, a meteorologist with the NWS, told the Associated Press that the nor’easter overall will be a "pretty slow mover". 

New Jersey Gov. Phil Murphy on Sunday declared a state of emergency in order to deploy resources. He also closed all state government offices for nonessential personnel and the state’s six mega sites that distribute COVID-19 vaccines. 

In New York, Connecticut and Rhode Island, many vaccination appointments for Monday needed to be canceled as well. 

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Amtrak canceled all Acela service between Boston and Washington and Pennsylvanian service between New York and Pittsburgh. Amtrak’s Northeast Regional, Keystone Service and Empire Service were operating on limited or modified schedules.

All New Jersey Transit trains and buses were suspended, except for the Atlantic City Rail Line. New York Waterway ferries were suspended.

Fox News’ Brandon Noriega, Peter Aitken and The Associated Press contributed to this report.