A blizzard of possibly historic proportions battered the Northeast Friday into Saturday, and forecasters feared as much as two feet of snow and strong winds could shut down densely populated cities such as New York and Boston, where cars were ordered off the streets.
State officials declared states of emergencies throughout the region, and utilities estimated more than a half-million customers were without power by late Friday night.
Some wondered if the storm could top Boston's all-time single-storm snowfall record of 27.6 inches, set in 2003.
By 9 p.m. Friday, according to the National Weather Service, the storm was spinning off the coast of Long Island, N.Y., and expected to move north-northeastward past New England's coast before its effects tapered off on Saturday afternoon.
"Storm total snowfall accumulations of 1 to 2 feet ... with locally higher amounts are possible across much of the Northeast," the National Weather Service said. "The heaviest snow is forecast to fall across parts of eastern Massachusetts ... Connecticut and Rhode Island where snowfall amounts higher than two feet are possible. In addition to the heavy snowfall ... wind gusts as high as 70 mph are possible ... especially near the coasts."
By 9 p.m. Friday, parts of Connecticut and New York had the highest actual snowfall totals listed by the National Weather Service, with 13 inches measured in Ogdensburg and East Setaukey, N.Y., and Lisbon and North Branford, Conn.
Peak wind gusts included a 71-mph measurement in Buzzards Bay, Mass., the National Weather Service said.
Power outages also were reported across the region. As of 11 p.m. Friday, for instance, approximately 300,000 Massachusetts customers were without power, ABC News station WCVB reported. Utilities also reported approximately 170,000 without power in Rhode Island, 30,000 in Connecticut and nearly 20,000 in New York.
The blizzard conditions came together after a storm from the west joined forces with one from the south to form a nor'easter.
The storm showed the potential for such ferocity that, before it even hit with full force, Massachusetts Gov. Deval Patrick declared a state of emergency Friday afternoon and signed an executive order banning vehicular traffic on roads in his state effective at 4 p.m. ET. It was believed that the last time the state enacted such a ban was during the blizzard of 1978. Violating the ban could result in a penalty of up to a year in jail and a $500 fine.
"[It] could definitely be a historic winter storm for the Northeast," said Adrienne Leptich of the National Weather Service in Upton, N.Y. "We're looking at very strong wind and heavy snow and we're also looking for some coastal flooding."
Airlines began shutting down operations Friday afternoon at major airports in the New York area as well as in Boston, Portland, Maine, Providence, R.I., and other Northeastern airports. By early evening Friday, more than 4,300 flights had been cancelled on Friday and Saturday, according to FlightAware. Airlines hoped to resume flights by Saturday afternoon, though normal schedules were not expected until Sunday.
The snow fell heavily Friday afternoon in New York City. Mayor Michael Bloomberg said clearing the roads was his main concern, and the city readied 1,700 snow plows and 250,000 tons of salt to clear the streets.
New York City was expecting up to 14 inches of snow, which started falling early this morning, though the heaviest amounts were expected to fall at night and into Saturday. Wind gusts of 55 mph were expected in New York City.
"Stay off the city streets. Stay out of your cars and stay at home while the worst of the storm is on us," Bloomberg said Friday.
Connecticut Gov. Dannel P. Malloy declared a state of emergency, deploying National Guard troops across the state to assist in rescues and other emergencies. Schools and state courthouses were closed, and all flights after 1:30 p.m. at Bradley Airport, north of Hartford, Conn., were cancelled. The state's largest utility companies planned for the possibility that 30 percent of customers -- more than 400,000 homes and businesses -- would lose power.
Malloy also directed drivers to stay off the state's major highways.
"Please stay off of 95, 91, 84, Merritt Parkway and any other limited-access road in the state," he said Friday evening.
Boston, Providence, R.I., Hartford, Conn., and other New England cities canceled school today.
"Stay off the streets of our city. Basically, stay home," Boston Mayor Tom Menino warned Thursday.
On Friday, Menino applauded the public's response.
"I'm very pleased with the compliance with the snow emergency," he said. "You drive down some of the roadways, you don't see one car."
Friday evening, Gov. Patrick also applauded the public's cooperation with the statewide vehicle ban, noting the clear roads were helping utility crews get their work done.
"It's been a great, great help and I thank everyone," Patrick said. "I know it's been an imposition."
As of 4:30 p.m. Friday, according to the Department of Defense, 837 National Guard soldiers and airmen under state control had been activated in Connecticut, Massachusetts and New York in anticipation of the storm -- 552 in Massachusetts, 235 in Connecticut and 50 in New York. The extra hands were helping with roadways, transportation, making wellness checks on residents and other emergency services.
Beach erosion and coastal flooding was possible from New Jersey to Long Island, N.Y., and into New England coastal areas. It was feared some waves off the coast could reach more than 20 feet.
Blizzard warnings were posted for parts of New Jersey and New York's Long Island, as well as portions of Massachusetts, Rhode Island and Connecticut, including Hartford, New Haven, Conn., and Providence. The warnings extended into New Hampshire and Maine.
To the south, Philadelphia was looking at a possible 4 to 6 inches of snow.
In anticipation of the storm, Amtrak said its Northeast trains would stop running this afternoon.
Parts of New York, still reeling from October's Superstorm Sandy, were still using tents and were worried about how they would deal with the nor'easter.
"Hopefully, we can supply them with enough hot food to get them through before the storm starts," Staten Island hub coordinator Donna Graziano said.
Ahead of the storm, residents of the Northeast piled into crowded supermarkets and hardware stores to purchase food and supplies. Others gassed up their cars in advance, braving long lines and wait times.
Cambridge, Mass., resident Rainy Neves detailed what she was stocking up on.
"Honestly, a lot of junk -- a lot of quick things you can make just in case lights go out, a lot of snacks to keep the kids busy while they'd be inside during the storm, things to sip with my friends, things for movies," she said. "Just a whole bunch of things to keep us entertained."
The fire department was called in to a grocery store in Salem, Mass., because there were too many people in the store Thursday afternoon trying to load up their carts with essential items.
"I'm going to try this roof melt stuff for the first time," Ian Watson of Belmont, Mass., said. "Just to prevent the ice dam. ... It's going be ugly on that roof."
ABC News' Danielle Genet and Max Golembo, and The Associated Press contributed to this report.