(CNN) Severe weather is expected to stretch from coast to coast on Tuesday, with about 75 million people under some sort of winter alert.

Throughout the Northeast, snow earlier in the day transitioned to freezing rain and will eventually become rain.

The metropolitan areas of New York and Boston could see 4 inches of snow followed by a coating of ice. Interior sections of the Northeast could see a foot or more of snow, while the storm is mainly expected to drop freezing rain in southern Pennsylvania and Maryland.

More than 850 flights into and out of John F. Kennedy and LaGuardia international airports in New York had been canceled as of Tuesday evening, according to FlightAware. More than 2,500 flights involving US airports were canceled.

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