Some of the U.S.'s biggest cities braced for what's expected to be another mammoth snowfall in the Midwest and the Northeast — with as much as a foot and a half forecast through Friday.
Winter storm warnings stretched from Chicago through the New York tri-state region into New England — affecting an area home to almost 40 million people.
The National Weather Service issued a blizzard warning for Nassau and Suffolk counties on Long Island in New York beginning at 6 p.m. ET Thursday, predicting inch-an-hour snow with 45-mph winds during the worst of it Thursday night.
"It's going to be a pretty significant storm, which will cause major travel disruption for a lot of people early in the new year," said Dave Houtz, senior meteorologist for The Weather Channel. "Any untreated roads will be a real mess."
In New York City, which was warned to expect 5 to 8 inches of snow through Friday, the administration of newly minted Mayor Bill DeBlasio said it would do its best to keep outdoor subway, Long Island Rail Road and Metro-North trains moving, calling out the Metropolitan Transportation Authority's ice-busting equipment.
Bus riders might not be so lucky: If roads become impassable, bus service will be suspended, the MTA said.
Get the latest weather news and your local forecast
In Boston, Mayor Tom Menino — in his last official act in office — pre-emptively declared a snow emergency for Thursday and closed the city's schools Friday as weather models pointed to up to 18 inches of new snow.
"What a New Year's gift, to receive one last snowstorm as mayor," Menino said Wednesday.
Buffalo was also predicted to get a 12- to 18-inch wallop, and accumulations of 8 to 12 inches were expected in areas of Maine and Vermont farther north.
What changed the forecast so drastically from Tuesday, when meteorologists said the storm wouldn't be a big deal, was the expected convergence of three separate low pressure systems roaring in from the south and the east.
They're hauling warm, wet air on a course straight for the frigid Northeast, said Greg Postrel, a forecaster for The Weather Channel.
"That's setting up for a big snowstorm for New England," Postrel said — "big" as in near-zero visibility and howling winds with wind chills well below zero.
The storm system was already walloping Chicago and Detroit, which were under several inches of snow Wednesday, with 5 to 8 inches more on the way.
More than 600 flights due in or out of Chicago's O'Hare International on Wednesday had been canceled by 10 p.m. ET, according to the flight-tracking website FlightAware.
In Toledo, Ohio, where 8 inches was expected, crews have been working nonstop.
"Our job is to keep the roads safe for the traveling public," David Pratt, the city's acting commissioner of streets and bridges, told NBC station WNWO of Toledo. "We've been out since Monday evening working 12-hour shifts."
“It's beautiful. It's like a white Christmas all over again," Rob Becht of South Bend, Ind., which was expected to get as much as 3 more inches of snow overnight on top of the several inches already on the ground.
“I'm just snow-blowing the sidewalks for the block," Becht told NBC station WNDU of South Bend. "I bought this expensive blower a couple years ago — why not take it out for a run?"
The snow also didn't deter hockey fans — it's a game played on ice, after all — in Ann Arbor, Mich., where the Detroit Red Wings and the Toronto Maple Leafs drew a world-record crowd of 105,491 for the annual Winter Classic outdoor game on Wednesday.
Temperatures at Michigan Stadium were in the low teens as snow fell steadily over the ice, with a wind chill of zero. Crews simply shoveled the snow off the ice during stops in play, and the Leafs ended up winning 3-2 in an overtime shootout.