(Bloomberg) -- A blizzard watch has been posted from Virginia toLong Island, including Washington and New York, for a storm thatthreatens to bring high winds and heavy snow starting Friday andlasting through the weekend.

Washington and Baltimore have a good chance of getting more thana foot (30 centimeters) of snow. Philadelphia could receive almostas much, and New York may see 6 to 12 inches, Patrick Burke, ameteorologist with the U.S. Weather Prediction Center in CollegePark, Maryland, said Thursday. High winds along the coast raise thechances for blizzard conditions.

“Use this advance notice to plan ahead,” the National WeatherService said in a bulletin. “Adjust travel plans and plannedactivities. Stock up on necessities. Prepare for the possibility ofpower outages during snowy and cold conditions.”

The snow should begin falling in Washington before sundownFriday, with heavier amounts arriving overnight, Burke said. In NewYork, the heaviest accumulations will come on Saturday, which iswhen Boston may get some snow as well. The storm has also touchedoff winter storm warnings and advisories from Arkansas and Kansasto Pennsylvania.

Boston outlook

“Boston is one of the more difficult locations to forecast forthis storm,” Burke said. “Any kind of shift of the track of thestorm could bring heavier amounts.”

The most likely forecast for Boston, still reeling from memoriesof the more than 9 feet of snow it received last year, is for 3inches in the city with as much as 7 inches across southeasternMassachusetts, according to the weather service.

The trend in forecast models has been for the storm to stayfarther south, and if that continues Boston could be spared, saidSteve LaVoie, a meteorologist at Hometown Forecast Services Inc. inNashua, New Hampshire.

Areas of Virginia and Maryland might get upward of 2 feet ofsnow. The storm will be slow-moving in much of the region.

In New York City, Mayor Bill de Blasio said trucks carrying rocksalt will begin hitting the streets Friday with crews operating12-hour shifts through the weekend.

Southern impact

Winter weather is already affecting Washington. Schools in thecity opened two hours later than usual Thursday because of frigidtemperatures, according to Mayor Muriel Bowser’s website. VirginiaGovernor Terry McAuliffe declared a state of emergency and askedresidents to stay off roads during the storm.

“This is going to be a very significant snow storm forWashington,” LaVoie said. “We are talking about measuring this infeet for Washington instead of inches.”

The storm may take its time moving through the region.

“It is a pretty lengthy storm; there may be a 36-hour window ofmoderate to heavy snow,” Burke said.

Some airlines have begun waiving change fees for people wantingto avoid airports this weekend.

--With assistance from Henry Goldman.

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