A dreaded "bomb cyclone" is pounding the Northeast, dumping blinding snow hurled by wind gusts as strong as 60 mph.
Parts of New England will be covered by 12 inches of snow. And by week's end, Boston and part of New Hampshire will be colder than Mars.
The bomb cyclone, which happened overnight, occurs when a cyclone has a significant and rapid drop in atmospheric pressure over a short period of time.
That spells blizzard conditions in the Northeast -- as well as thousands of canceled flights, scores of shuttered schools and empty grocery store shelves.
•Storm moves north: Damaging winds and heavy snow are the main concern Thursday. About 3 to 6 inches of snow are expected in Philadelphia, 4 to 8 inches in New York City, and more than a foot of snow in Boston, forecasters said.
•Power outages: More than 40,000 customers in Virginia and North Carolina lost power early Thursday, according to energy provider Dominion Energy. More than 8,000 customers were also without power in Florida, according to Duke Energy.
•Schools closures: Classes have been canceled Thursday in New York and Boston. Buffalo schools are set to close on Friday amid the cold temperatures, officials said.
•Storm is snarling roads and air travel: More than 2,700 US flights on Thursday have been canceled, according to Flightaware.com. More than 90% of Thursday flights from LaGuardia Airport in New York City are canceled, and American Airlines suspended all departures from Boston.
•Deadly cold: At least 12 people in the US have died this week owing to factors related to the cold, officials said. Six deaths were reported in Wisconsin, four in Texas, one in North Dakota and one in Missouri.
•Rare snow sightings: Some areas of Charleston, South Carolina, saw more than 5 inches of snow Wednesday. In Tallahassee, Florida, there was less than an inch of snow, but for many, it was their first-ever in-person sight of snow.
Blizzard-like conditions threaten states
In Connecticut, where the storm is expected to hit Thursday, Gov. Dan Malloy urged motorists to stay off roads. The forecast calls for a minimum of 6 inches of snow and winds as strong as 50 mph, potentially hindering utility repairs should power lines go down.
"We cannot and will not order people up in trucks to fix lines when the winds are too high," Malloy said.
Virginia Gov. Terry McAuliffe declared a state of emergency and urged Virginians to prepare for the storm, which could dump up to a foot of snow in portions of eastern Virginia.
"The bitter cold that continues to plague the Commonwealth will be joined by a potentially significant winter storm which will blast Hampton Roads, the Northern Neck, Eastern Shore and other areas of Eastern Virginia with snowfall and blizzard-like conditions in some communities," McAuliffe said Wednesday.
"With this forecast in mind, all Virginians should take the necessary precautions now to ensure they are prepared for the travel disruptions, power outages and other threats to health and safety that could arise during this significant weather event."
Expect more bone-chilling temperatures
The weather phenomenon, known as bombogenesis, will also usher in on Thursday another round of single-digit or subzero temperatures to the Northeast.
In New York and Philadelphia, temperatures are expected to dip to 3 degrees this weekend.
New York City schools are closed Thursday and sanitation workers are preparing to deploy 2,200 plows to help clear the streets, with 4 to 6 inches of snowfall expected. The snow, combined with "exceptionally strong winds," means crews will be working in near-whiteout conditions, New York City Sanitation Commissioner Kathryn Garcia said.
Boston could see minus 7 degree temperatures paired with about 12 inches of snow, forecasters said.
Massachusetts Gov. Charlie Baker said the greatest areas of concern are along the Plymouth County coast, from Sandwich to Dennis on Cape Cod.
Snowfall blankets the Southeast
Before the storm pushed north, cities in the Southeast that rarely see snow turned into winter wonderlands, with snow weighing down palm fronds and freezing water in fountains.
Dozens of car crashes also were reported and several airports closed.
Runways at Charleston International Airport closed and the South Carolina Highway Patrol reported dozens of wrecks as snow and sleet fell. In Georgia, the Savannah/Hilton Head International Airport -- typically booming with tourists this time of year -- closed on Wednesday due to severe winter weather conditions.
In South Carolina, some areas had seen 5 to 6 inches of snow by Wednesday afternoon, requiring more than 13,000 tons of salt, Gov. Henry McMaster said.
Steady snowfall blanketed Charleston, recording at least 5.3 inches on Wednesday. It was the most snow the city has seen in one day since 1989 and the third-highest snowfall total on record.
McMaster warned of dangerous conditions as evening temperatures were expected to remain below freezing through Monday. He also urged people to stay indoors as much as possible to minimize risk of injury.
Measurable snow also fell in Tallahassee, Florida, marking the first time that had happened since 1989, CNN meteorologist Michael Guy said.
Bomb cyclones feed on cold air
Bomb cyclones can draw colder air in from the north, then blast out icy temperatures.
They frequently occur in North America, when cold air collides with warm air over the Atlantic Ocean, though they've also been reported in eastern Asia and South America.