The northeastern U.S. is bracing for a powerful, fast-moving storm that is expected to bring more than a foot of snow in some places.

Forecasters say the Thursday snowstorm likely will snarl workday commutes across the densely populated region. It has the potential to be the most powerful storm that some areas have seen in a mostly snow-free winter.

The National Weather Service predicts that the Boston area and eastern Maine will get 12 to 18 inches of snow, New York City could see 8 to 12 inches and the Philadelphia area 4 to 8 inches. Near whiteout conditions are possible, with the snow expected to fall at a clip of 2 to 4 inches per hour at its peak.

Officials also are warning of high winds, coastal flooding and power outages.

A number of school systems already have canceled Thursday classes including New York City, Philadelphia and Boston. Airlines scrapped thousands of flights by late Wednesday as a precaution.

The storm comes a day after much of the Northeast enjoyed a brief glimpse of spring, with temperatures hitting 60 degrees in some places.

Thursday’s storm is expected to last 6 to 10 hours, said Carl Erickson, a senior meteorologist with AccuWeather in State College, Pennsylvania.

It will hit eastern Pennsylvania and northern New Jersey with rain early Thursday morning, before changing over to snow in time for the morning rush, he said. New York City could see the first flakes by 3 a.m., while Boston and other parts of New England should expect the snow to start around 5 a.m.

The snow is expected taper off by the early afternoon in the Philadelphia and New York City areas, but New Englanders should brace for snowfall through the evening commute.