Heavy snow is expected to blanket large portions of the Eastern U.S. while much of the country will endure dangerously cold temperatures in the coming days.

The snow is likely to fall on Sunday from the Appalachians to New England. New York City may see its largest snowfall in years.

"The level and extensiveness of the frigid air may be tough to match the rest of the winter," forecasters warned.

Snow was falling in the Mid-Atlantic and New York City on Sunday. The coldest air in several years will descend across much of the country starting Monday, forecasters said.