(Bloomberg) -- At least 50 million people are in the path of aparalyzing winter storm that prompted the cancellation of thousandsof flights, closed government offices, and threatens Washingtonwith one of its worst snowfalls on record. New York is bracing fora blizzard.

More than 2 feet (61 centimeters) of snow should start fallingin Washington and Baltimore later Friday before moving up thecoast, according to the National WeatherService. New York will start to get snow Saturday and willprobably see more than 6 inches along with heavy winds.

“There are blizzard warnings for the whole corridor fromWashington to Philadelphia, New York and Long Island,” said DanPetersen, a meteorologist with the U.S. WeatherPrediction Center in College Park, Maryland. “It is going toput us in the top couple of snowstorms down here. It’s a historicsnow storm.”

The heaviest three-day snow to fall in the Washington area was28 inches in January 1922, according to the weather service.Baltimore received 26.8 inches in February 2003. While the EastCoast cities bear the brunt of some of the heaviest snow, the stormis a national event, with a tornado and severe thunderstorms acrossthe South and an ice storm stretching from Kentucky into NorthCarolina.

Alerts posted

Winter storm warnings and advisories stretch from Louisiana toMassachusetts.

“Right now things are progressing as they have been forecast,”said Tyler Roys, a meteorologist with AccuWeather Inc.in State College, Pennsylvania. The leading edge of the snow wasmoving toward Washington at midday after blanketing parts of theSouth, he said.

More than 38,000 homes and businesses from Arkansas toPennsylvania were blacked out as of about noon New York timeFriday, according to utility websites.

“It has the potential to be an extremely dangerous storm,” LouisUccellini, director of the National Weather Service, said Thursdayin a conference call with reporters. “It is a potentiallyparalyzing storm.”

Travel trouble

New York City Mayor Bill de Blasio urged people to avoidtraveling Saturday and Sunday. In Washington, federal officesclosed at noon, according to the Office of PersonnelManagement’s website. Public schools closed and WashingtonMetro will halt city buses at 5 p.m. and rail travel at 11 p.m.Both bus and subway services will remain shut through Sunday.

One major Washington event will go on as scheduled: the annualMarch for Life marking the Roe v. Wade anniversary, theevent’s organizers said in a release. The White House has canceledtours on Saturday.

Almost 5,550 flights around the U.S. were grounded for Fridayand Saturday as of 11:45 a.m. New York time, according toHouston-based FlightAware, an airline trackingservice. Most were in the New York and Washington areas.

Amtrak canceled several trains in the East Coast and across theSouth. North Carolina, South Carolina, Virginia, West Virginia andGeorgia lifted some trucking restrictions to help expedite fueldeliveries.

NYC outlook

New York can expect 6 to 10 inches, said Steve LaVoie, ameteorologist at Hometown Forecast Services Inc. in Nashua, NewHampshire. The high winds associated with the storm and periods ofheavy snow triggered New York and Long Island blizzard warnings.Wind gusts of 50 miles per hour are possible in Manhattan and therest of New York starting Saturday into Sunday, the weather servicesaid.

The line between heavy snow and not much at all will be a fineone in the New York area, so the area just north of the city willprobably have amounts drop off sharply. At the same time, NewJersey could end up as much as 18 inches, the weather servicesaid.

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Roys said meteorologists are still trying to pinpoint where thatline will be.

“Over a very short distance, there will be a great gradient froma lot to nothing,” Roys said. “That is the one thing that we arestill trying to figure out.”

Boston will probably be spared any real problems. The city thatsaw a record snowfall last year may get 2 inches by Sunday,according to the weather service.

“In Boston, it’s still not a big deal,” LaVoie said.

--With assistance from Mark Chediak, Steven T. Dennis, MarySchlangenstein, Lars Paulsson, Angela Greiling Keane, Jim Polsonand Laura Blewitt.

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