BANGOR, Maine — What forecasters say will be the biggest snowstorm so far this winter is on target to hit Maine Sunday night and could stick around until late Monday night.

By the time the storm — the third to hit the state in less than a week — is over, as much as two feet of fresh snow will have fallen in Greater Bangor and Down East, according to the National Weather Service.

The storm is the result of a low-pressure system tracking eastward across the Ohio Valley and mid-Atlantic region that is expected to intensify rapidly Sunday night and Monday after it passes through the New England coast, according to Reuters.

“It will become a powerful nor’easter with blizzard conditions expected for parts of Maine as the winds become quite strong,” the weather service said.

Coastal New England could experience flooding and widespread windy conditions with potential gusts greater than 50 mph expected as far west as the central Appalachians and mid-Atlantic region, the weather service said.

“At this time, the corridor expected to be in the bull’s-eye of heaviest snow will be portions of central and eastern Maine, including Bangor and Bar Harbor,” according to AccuWeather.

The Northeast is coming off the fiercest snowstorm of the winter, which dumped more than a foot of snow in some areas Thursday, causing thousands of flights to be canceled and schools to be closed.

A blizzard warning is in effect for southern Penobscot, coastal and central Washington, and coastal and Washington counties, interior and coastal Hancock and Waldo counties and Sagadahoc, Lincoln and Knox counties, which are expected to be hit hardest, with expected accumulations of 18 to 24 inches of snow Sunday night through Monday night, forecasters said Sunday afternoon.

Heavy snow combined with winds of up to 55 mph are expected to lead to whiteout conditions, making travel extremely dangerous and posing a risk of power outages.

Emera Maine said it has put crews and equipment in place throughout its service area and staff at its Customer Contact Center to deal with any storm-related outages.

It urged customers to make sure they have flashlights, spare batteries, a supply of clean water and nonperishable food items on hand in case the power goes out, and to make sure any secondary heating systems that do not depend on electricity are in good working order and have an adequate fuel supply.

Meanwhile, a winter storm warning was in effect for parts of York, Cumberland, Androscoggin, Oxford, Somerset and Franklin counties, which also are expected to get 18 to 24 inches of snow but lesser speed winds during the storm.

Meanwhile, northern Penobscot and Washington counties, as well as all of Piscataquis and southeast Aroostook counties, were expected to get between a foot and 18 inches of snow late Sunday night through early Tuesday morning, with wind gusts of up to 35 mph.

Forecasters expected northern Aroostook and Somerset counties to escape the brunt of the storm, with only 6 to 10 inches of snow expected.

Snow already was causing problems in southern Maine as of noon Sunday, according to the Maine Turnpike Authority, which reported that the Cumberland County Regional Communications Center dispatchers said that Route 100 in New Gloucester, between Intervale Road and the Auburn town line, was shut down due to numerous slide-offs and crashes.

By 2:30 p.m. on Sunday, the speed limit for the Maine Turnpike from the New Hampshire line to its end at Mile 109 had been reduced to 45 mph because of snow.

Motorists were advised to seek alternate routes.

Cancellation announcements already were pouring in early Sunday afternoon, as more than 200 government, school, business and other establishments planned to be closed Sunday night and Monday. By midafternoon, the number had climbed to more than 350.

Among the closings were classes at the University of Maine in Orono, the University of Southern Maine’s campuses, Husson University’s Bangor and Westbrook campuses and the New England School of Communications.

Eastern Maine Medical Center said some of its services would not be available on Monday because “one of the most dangerous winter storms in recent memory” was headed its way.

Due to the severity of the storm, the cities of Bangor and Portland said they were shutting down all non-emergency departments for the entire day on Monday. All State Legislature offices also will be closed.

Old Town Police Chief Scott Wilcox announced a citywide parking ban from Sunday night through 10 a.m. Tuesday for all public roadways.

In addition, numerous flights that were expected to arrive at and depart at Bangor International Airport had been canceled as of Sunday afternoon as were all scheduled flights at Portland International Jetport.

Greater Portland’s METRO bus system will not be operating on Monday but it was not yet clear if the Communiy Connector would be running as of late Sunday afternoon.