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(CNN) —  

A storm system causing severe weather Sunday along the Gulf Coast is forecast to move off the East Coast, turn into a nor’easter and threaten the Northeastern United States on Monday night into Tuesday.

The storm’s exact path remains a bit uncertain, but the system will bring precipitation and wind in what will be the third significant winter storm in the past 10 days.

A winter storm watch is in effect for 8.5 million people in New England, including residents of Boston and Portland, Maine. The National Weather Service Boston estimated 6 to 8 inches of snow for parts of Massachusetts, Rhode Island and Connecticut.

New York, Philadelphia and Washington are only under a hazardous weather outlook at this time. The next forecast update will come at 8 p.m. on Sunday.

Related: Track the storm

The American model forecasts heavy snowfall for areas of New England and upstate New York, whereas the European model shows less snowfall. Still, both models agree there will be more snow on the way for the Northeast.

If the nor’easter tracks closer to the coast, then stronger winds and coastal flooding may become issues as well.

Last weekend, a powerful nor’easter that morphed into a “bomb cyclone” slammed much of the Northeast with heavy snow and rain, hurricane-force wind gusts, and significant coastal flooding. The storm left six people dead from falling trees, and about 900,000 people lost electrical power.

As residents were still digging out from that snow, a second storm hit the Northeast late last week. The storm dropped heavy, wet snow in areas west of Interstate 95, leaving feet of snow in some areas. One 88-year-old woman died Wednesday when a tree fell and struck her in Suffern, in southern New York, police said.

This winter’s snowfall totals so far sit around the annual average at this point for the major Northeast hubs of Boston, New York and Philadelphia, according to the National Weather Service.

CNN’s Allison Chinchar contributed to this report.