A second nor'easter barreled down on the Northeast on Wednesday, promising to snarl the evening commute with heavy snow just days after a deadly winter storm left hundreds of thousands of customers without power.
Forty-eight million people from Maryland to Maine were facing winter storm advisories Wednesday from the storm, part of a system that has dumped snow across the country since it first hit the West Coast late last week.
Photos: Nor'easter slams East Coast ... again
Witnesses reported lightning and peals of thunder across the region during the snowstorm — a rare phenomenon called "thundersnow."
The new storm canceled thousands of flights and was making roads treacherous in major cities, including Philadelphia, New York and Boston.
"We're starting now to see deteriorating conditions in New York and Philadelphia, the heavy snow signature we were expecting," said Brian Hurley, a meteorologist at the National Weather Service's Weather Prediction Center. "It's going to envelop those areas right through rush hour."
"And with the roads extremely slippery," he added, "driving in it is not going to be fun."
While last Friday's storm pummeled the Interstate 95 corridor with strong rains and winds, this time the danger comes from snow — and a lot of it. At its peak, the nor'easter is projected to blanket the region with snowfall rates of up to 3 inches an hour.
Reinforced by a cold front moving offshore to the Atlantic, the storm was expected to intensify into Thursday morning as it moved north.
With the storm track having shifted from original projections, part of the Philadelphia-New York corridor — one of the most populated regions in the country — were particularly hard hit, forecasters say. North Caldwell, New Jersey, had already been blanketed with 19 inches by 5:30 p.m., and New York City was projected to get 6 to 12 inches of snow after the temperatures dropped at nightfall.
"We're now right in the thick of it," said NBC News meteorologist Sherri Pugh. "Travel is already being impacted and it's going to continue to be dangerous through tonight's commute."
Related: Another nor'easter heads for East Coast
A cascade of cancellations and delays were already being felt as the brunt of the storm rolled through the Northeast.
More than 2,600 departures and arrivals were scrapped at airports in Boston, Philadelphia, New York and Newark, New Jersey. Amtrak canceled many trains usually scheduled to run in the corridor between Washington and Boston. New Jersey State Police responded to more than 50 multiple-vehicle crashes by noon because of the icy conditions.
A New Jersey teacher was listed as stable condition after being struck by lightning outside Manchester Township Middle School during the height of the thundersnow, according to police.
Ten people were hospitalized with carbon monoxide poisoning from a generator that had been powered up inside a home in White Plains, New York, The Associated Press reported.
But a bigger worry was that some of the regions that were still repairing downed power lines and damage from coastal flooding from last Friday's storm were particularly susceptible. The coastal town of Duxbury, Massachusetts, was still recovering from devastating flooding after part of its seawall was demolished by the previous nor'easter.
"The work we've been doing out on the seawall has been holding up, which we're pleased with," Town Manager Rene Read told NBC News hours before the worst of the storm was supposed to hit Wednesday night. "We've heard that there could be 40- to 50 mile-an-hour gusts of wind. We do have high tides, and that's a big sea out there. ... We're tired [from the last five days] but morale is good."
Even though Wednesday's storm wasn't predicted to bring as much flooding or strong gusts, there were worries about more strains to power lines already weakened from the heavy winds on Friday, this time from heavy, wet snowfall.
"A lot of the same places that were hit hard on Friday will have impacts from this system," Pugh said.
More than 500,000 customers were without electricity early Wednesday evening in New York, Pennsylvania, New Jersey and Connecticut, utility companies reported.
In Mamaroneck, New York, in Westchester County, frustrations were building as parts of the area waited for power to be restored from the first wallop — while bracing for the next one.
The estimated restoration time from Con Edison "seems to be a moving target," Mayor Tom Murphy told LoHud.com, "which is kind of disconcerting because it doesn't inspire confidence that they have a plan."
New York Gov. Andrew Cuomo also criticized the utility companies, vowing to review their response to the problem.
