A major nor'easter could bring blizzard conditions to the Boston area Monday, the latest weather forecast shows.

The National Weather Service says that it issues blizzard warnings "for winter storms with sustained or frequent winds of 35 mph or higher with considerable falling and/or blowing snow that frequently reduces visibility to 1/4 of a mile or less. These conditions are expected to prevail for a minimum of 3 hours."

Projected snowfall totals for New York City and Boston range from a foot to 2 feet of snow. Philadelphia could receive up to 18 inches of snow, while Washington, D.C., is forecast to get 3 to 6 inches.

A blizzard warning is issued when snow accumulations are expected between 13 and 18 inches and winds are expected to gust as high as 55 mph.

On Sunday at 11:16 a.m. the National Weather Service released a blizzard warning valid from 4 p.m. until Tuesday 7 a.m. for Worcester, Middlesex, Essex, Hampden and Hampshire counties.

Delays and cancellations climbed well into the hundreds Sunday at Logan Airport as a potentially historic nor'easter closed in New England.

What you should knowA blizzard warning is in effect as a massive winter storm is expected to drop more than a foot of snow in and around Philadelphia through Monday.Snow is expected to begin falling by midday Sunday and continue through Monday afternoon,

After a week of uncertain forecasts, Cape Cod is under a blizzard warning, part of a "significant" nor'easter expected to hit Massachusetts Sunday, all day Monday, and into Tuesday. The blizzard warning begins at 4 p.m. Sunday for all 15 Cape Cod towns and Martha's Vineyard, and it remains in effect until 7 a.m. Tuesday.