Intense bands of snow are whipping parts of the Northeast, threatening dangerous driving conditions and more power outages Wednesday afternoon as the second nor'easter in a week hits the storm-weary East Coast.
More than 50 million people from Maryland to Maine are under winter storm warnings and watches, just days after last weekend's deadly "bomb cyclone." More than 2,600 flights have been canceled Wednesday.
Some areas outside Philadelphia already have seen the kind of fast and heavy snowfall that forecasters fear will plague motorists in New York and New England later Wednesday afternoon and evening.
Five to 7 inches fell near Gilbertsville, Pennsylvania, at rates of nearly 2 inches per hour in the late morning, the National Weather Service reported.
Huge snowflakes fell to the ground swiftly in eastern Pennsylvania late Wednesday morning in videos on social media.
The storm also could cause minor to moderate coastal flooding in the northern mid-Atlantic and Northeast, and winds and snow could bring down more power lines, adding to the thousands of outages that remain in the region from last weekend.
By Wednesday afternoon, parts of New York and New England could see snowfall at rates of 1 to 3 inches per hour, forecasters said.
Massachusetts Gov. Charlie Baker urged residents to use caution then.
"Everyone should expect a long and challenging commute this evening," Baker said during a news conference Wednesday morning. "Stay off the roads during the height of the storms this afternoon if you can."
Up to 1 foot possible along the coast, and more inland
Philadelphia, New York and Boston could see fair amounts of snow, but areas inland could receive even more.
Philadelphia could get about 8 to 12 inches, according to snowfall estimates from the National Weather Service, with especially heavy snowfall possible through 7 p.m. City schools were closed Wednesday, and all after-school activities canceled.
Pennsylvania Gov. Tom Wolf announced a state of emergency for several counties in preparation for the storm.
New York City could see 8 to 12 inches of snow, but public schools were open Wednesday, officials said. The heaviest precipitation will occur Wednesday afternoon, according to the National Weather Service's New York office.
In New England, Interstate 95 could be a key dividing line, with points west due to get as much as 2 feet of snow, and points east getting rain and lower amounts of snow, CNN meteorologist Dave Hennen said.
The Boston area may receive 6 to 8 inches of snow, with areas as little as 20 miles inland perhaps getting 12 or more inches. But if the rain/snow line moves farther east, Boston's snow accumulation would rise.
"It's a very dicey call for eastern MA. ... There's going to be a sharp line from little/no snow to several inches of accumulation," the National Weather Service in Boston tweeted.
The snowstorm came with a rare accompaniment of lightning in some parts of Pennsylvania, New Jersey and New York, the weather service said.
"Thundersnow," as the phenomenon is known, is snow paired with lightning and resulting thunder. To happen, the air layer closer to the ground must be warmer than those above but still cold enough to create snow.
Ground temperatures in the winter are usually too cold for thundersnow to occur.
How is it affecting travel?
Much of the 2,600-plus flight cancellations involve major airports in the Northeast, such as Newark, John F. Kennedy, LaGuardia, Boston and Philadelphia, according to tracking site FlightAware.
As for ground travel, New York City's Office of Emergency Management issued a hazardous travel advisory urging New Yorkers to "take mass transit if possible and allow for extra travel time."
Amtrak has also modified some of its services between Washington and Boston.
More than 50 million from Maryland to Maine are under winter storm warnings and watches
The region is still recovering from last weekend's "bomb cyclone"