The fourth nor’easter in three weeks is about to hit the U.S. Northeast, potentially dropping as much as a foot of snow on New York and Boston and shutting down government offices in Washington.

Snow is expected to start late Tuesday, hitting Washington with 4 to 8 inches (10 to 20 centimeters), which could be the heaviest snowfall in two years. New York could get as much as 14 inches starting Tuesday night and accumulating mainly on Wednesday, the National Weather Service said. Boston is forecast to get 11 inches.

“Confidence is growing it will produce some significant snow,” said Dan Petersen, a forecaster with the U.S. Weather Prediction Center in College Park, Maryland.

If the storm shuts down the federal government, as happened earlier this month, it may complicate the push to get legislation in place before a Friday midnight deadline to fund operations.

New Jersey Governor Phil Murphy said he may declare an emergency there late Tuesday.

“Please do not head out into the snow unless you absolutely have to,” Murphy said. There’s a chance for “the combination of gusty winds and wet snow, which could bring down power lines.”

Atlantic Flooding

Three storms have already ripped across the Northeast this month, dropping snow by the foot from Long Island to Boston. More than 2 million customers were without power during the worst of the nor’easters, which also caused high seas and flooding along the Atlantic coast from Massachusetts to New Jersey. More than 9,100 flights were canceled.

New York City has been targeted for heavy snow in some of the past storms only to dodge the worst as the systems developed. Two weeks ago, Manhattan got 3.2 inches, while just miles away in New Jersey, more than 20 inches fell.

The next set of modeling runs later Tuesday will be crucial in fixing the forecast for New York and other East Coast cities, said Shunondo Basu, Bloomberg New Energy Finance meteorologist and natural gas analyst. If the storm’s center tracks closer “New York City will be in the thick of it,” he said.

Snow totals may also be held down, especially in eastern areas right along the coast, because it will be compacted by rain and sleet, he said.

Two Waves

The latest system is hitting in two waves. It began early Tuesday in Washington and Baltimore with rain that’s expected to later change into sleet and freezing rain, said Rob Carolan, owner of Hometown Forecast Services Inc. in Nashua, New Hampshire.

The heavier snow will start late Tuesday in Washington and then come north to New York where the heaviest accumulations will greet morning commuters on Wednesday. Boston’s snow will start later on Wednesday.

“Boston is in the jackpot zone,” said Rob Carolan, owner of Hometown Forecast Services Inc. in Nashua, New Hampshire.

Closer to the coast and along the Interstate 95 corridor, the snow will be particularly wet and heavy and when combined with high winds can bring down branches and power lines raising the possibility of outages, Carolan said. A high wind watch has been issued for coastal Massachusetts.

In addition to the snow and winds, coastal flooding is expected to rake the coast. The new moon was just three days ago, so tides will be a bit higher than average, Carolan said. Minor to moderate flooding may occur from New Jersey to Massachusetts, the weather service said.

Winter storm warnings are in effect from western North Carolina to Massachusetts. As of 11:20 a.m., 378 flights were canceled around the U.S., mostly from Philadelphia, with another 259 scrubbed for Wednesday, according to FlightAware, a Houston-based airline tracking service.

“Severe winter weather conditions will make travel very hazardous or impossible,” the weather service said. “If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency.”

Once the storm passes, melting should start, Basu said.

“The beauty of March snowstorms is that it comes and goes before you know it,” Basu said. “Wall-to-wall sunshine on Friday and Saturday given the high sun angle of spring will melt snow quickly despite night-time lows below freezing.”