A massive blizzard began its brutal descent on the Northeast Friday bringing high winds, deepening show and threats of flooding to a region still scarred from Hurricane Sandy.

After a day of pelting wet snow, five states — New York, Massachusetts, Connecticut, New Hampshire and Rhode Island — had declared states of emergency, and Massachusetts had banned vehicles from every road in the state.

Downtown Boston was a ghost town lost in a swirl of snow.

The worst was expected Friday night and early today. Forecasters said the storm would continue through this afternoon, leaving behind a fresh white blanket perhaps three feet thick.

In New York City, Mayor Michael R. Bloomberg told people to stay home and warned them not to "panic buy" gasoline because the supply was plentiful. But the memory of Hurricane Sandy was still so raw that many across the region went on buying sprees anyway, emptying store shelves and filling extra containers of gasoline in addition to their car tanks.

"I don't think it's going to be as bad as they're saying, but I said that with Sandy too," said Lavel Samuels, 42, as she filled her tank at a gas station in Queens. "I'm filling up based on my experience with Sandy, in case there's no gas on Sunday or Monday."

That grim mood contrasted sharply with a more playful sense among some in New England, where the prospect of new snow thrilled skiers who have bemoaned almost two seasons of barren slopes.

"These aren't flakes falling from the sky, these are dollar bills," said Ed Carrier as he sat in a coffee shop in Portsmouth, N.H., and envisioned the boon for winter sports. Staff at the Thirsty Moose Taphouse nearby said they were determined to stay open through the duration of the storm until their regular closing time at 1 a.m. and even offered storm-related drink specials: $3 porters and stouts, as long as it was snowing. "It's just a little bit of snow," said the hostess, Kim Lovely. "Mother Nature's just brushing out her dandruff."

But in most cities and towns, Friday was largely a day of preparing for the worst. With hurricane-force winds, the Weather Service expects flooding along the Atlantic coast that could affect up to 8 million people.

Already by evening, thousands of power outages had been reported across Massachusetts, Rhode Island and Connecticut and utility officials were girding for more extensive disruptions in service. Predicted winds up to 75 miles an hour would likely topple trees and take down more power lines, officials said. Marcy Reed, president of National Grid, said outages could last several days because repairs would not begin until the storm ended and would require unearthing power lines buried under mounds of snow.

Maine declared a partial emergency, allowing it to suspend federal transportation rules, extend worker hours and bring in extra crews from Canada to assist with storm damage repair.

Thousands of flights were grounded on Friday and thousands more were expected to be suspended through the weekend.

By today, the total expected snowfall in New York City is expected to be between 10 and 14 inches. In Long Island, the snow totals will range from 14 to 18 inches, with the highest amounts at the east end.

Boston could break modern records by topping 28 inches.

Jerome Hauer, the New York state commissioner of the Division of Homeland Security and Emergency Services, said that coastal areas of Queens, Brooklyn and Long Island could experience flooding and that residents should be prepared to seek alternative shelter. While the storm surge is expected to be only 3 to 5 feet — well below the 14-foot surge that Hurricane Sandy delivered — he said large waves could bring water inland.

"If you see flooding, have plans for somewhere to go," Hauer said.