The National Weather Service said as much as 21 inches of snow was expected in the region, with a bit more farther south. Officials said 15 to 25 mph winds with higher gusts could produce near-blizzard conditions.
Philadelphia declared a snow emergency, warning that cars parked on streets designated as snow emergency routes would be towed. The city school district canceled all weekend activities, and many other organizations canceled events or closed early. The snowfall was expected to end early Sunday.
"If you don't need to get out today, don't go out," Philadelphia Mayor Michael Nutter told residents, urging them to check on their neighbors and help shovel their walks if needed. "We're going to fight this storm and do everything we need to do to make life as simple as possible."
Philadelphia International Airport said at least 70 percent of flights into and out of Philadelphia were canceled, spokeswoman Phyllis Van Istendal said. More cancellations were expected Sunday as the nation's aviation system tries to return to normal after a day of massive snowfall.
The Pennsylvania Department of Transportation began spraying roads with a salt solution Thursday and had mobilized all 402 trucks available for the five-county Philadelphia region. The agency had been deploying salt trucks and snowplows all day, and reported all major highways still passable Saturday night, PennDOT spokesman Charlie Metzger said.
Drifting snow could become a problem as the night progresses, he said.
Earlier Saturday, Kathryn Mariani said the snow wasn't about to stop her from taking the train down from the Germantown section of North Philadelphia to Liberty Place to buy a few more presents. She used the train ride to knit a few more gifts, and after filling out her Christmas cards at a mall table, she said the weather made everything more festive.
"It really helped me get in the Christmas spirit," said the 50-year-old Mariani. "I think it's beautiful. We were due a big snow."
Tim Brennan, 63, wore a Villanova University hat and was still celebrating the team's national championship a day earlier as he shoveled the walk Saturday outside his house in the Fairmount section of the city. He said he was glad he moved six years ago to the three-story row house from the suburbs, where he had a 300-foot driveway to shovel.
"It's a lot easier than the old days," he said. Still, with about an hour of work ahead, "the excitement of snow has passed," he added.
Debi Sacca was walking in the park near the Rodin museum on the mostly deserted Ben Franklin Parkway with her dog, Coco, whom she just got from Florida.
"This is Coco's first winter, so he's loving it," she said as the Labrador-pit bull mix pulled her along in the snow.
Meanwhile, several bicyclists rolled down the parkway carrying sleds and, farther downtown, adults used sleds to pull children along snow-covered sidewalks. First-time Philadelphia visitor Kate Rhodenburg, 24, of Lebanon, N.H., posed in front of the snow-covered "Love" statue in the park of the same name across from City Hall.
She and her friends then set off to see the Liberty Bell and grab cheesesteaks in South Philadelphia.
Traffic was down at the King of Prussia mall, which planned to remain open during the scheduled hours of 8 a.m. to 11 p.m., said Tyler Shaffer, assistant marketing manager. The slowdown was in contrast to Friday, when people flocked to the mall in an apparent effort to get a jump on their last-minute holiday shopping, he said.
"Certainly, the weather is hitting us hard today," he said. "We're not as busy today as we traditionally have been on the Saturday before Christmas. But this holiday season has been great so far, so we're optimistic for the rest of the week."
Associated Press Writer Patrick Walters contributed to this report.
Up to 15 inches of snow falls in southern NJ
Gusting winds and intensifying snowfall combined to make travel treacherous Saturday night, as road crews scrambled to keep major highways clear after as much as 20 inches of snow fell in the Philadelphia area.
The National Weather Service predicted that as much as 21 inches of snow could fall in Philadelphia and southern and central New Jersey by the time the storm ends early Sunday. Winds gusting as high as 40 mph were expected to create whiteout conditions in many areas.
The winter storm was the worst that many parts of the region had seen since February 2006.
A winter storm warning was in effect for all of New Jersey through early Sunday, while coastal flood warnings and high surf advisories also were issued. Scattered power outages were reported in many areas.
By evening, many areas had over a foot of powdery snow - the kind that's too dry for snowballs.
The highest in the area was 21 inches in the Philadelphia suburb of Tabernacle. Sixteen inches had been recorded at Philadelphia International Airport at 7 p.m.
Philadelphia's northern and western suburbs, usually hit harder by snow, were getting less. And in northern New Jersey, forecasters were expecting no more than 8 inches.
Libraries closed and holiday parties were called off, and Freehold Raceway canceled its live harness racing card and simulcasting wagering. Other major sporting events were still on, though the scheduled start of Sunday's NFL game between the Philadelphia Eagles and the San Francisco 49ers was pushed back from 1 p.m. to 4:15 p.m. in a bow to the weather.
The majority of the day's scheduled flights were canceled at major airports in the mid-Atlantic region, including at least 70 percent in both Philadelphia and Newark.
Speed limits were reduced on major highways, but that wasn't enough to keep cars from spinning into ditches.
David Weinstein, a spokesman for AAA Mid-Atlantic, said the auto club was taking about 500 member calls an hour Saturday night but handled as many as 800 calls an hour earlier in the day.
About 60 percent of the calls were for extraction from snow banks and drifts after vehicles skidded, Weinstein said. AAA put chains on the tires of the trucks it owns "to help navigate what are some of the worst conditions we've seen in many years in the Garden State," he said.
By evening, snowfall in Philadelphia's New Jersey suburbs was more than a foot and still coming down, the roads were slippery and traffic was sparse for a day that under normal conditions would have been among the busiest shopping days of the year.
Lucy and Jon McCoy and their three daughters were among the brave souls who ventured out. With confidence boosted by their red Dodge pickup, they traveled more than 50 miles from their home in the shore community of Forked River to the Cherry Hill Mall for their big holiday shopping trip.
By the time they arrived, many of the stores had closed. When they left, hungry, restaurants like Olive Garden and Red Lobster were closed, too.
The storm also was felt at Atlantic City casinos, where gamblers were in low numbers at most gaming halls.
At Harrahs Resort Atlantic City, rows of slot machines sat idle, restaurants were sparsely filled or closed and the casino's massive indoor pool was to close early because of the weather. The storm lashed the gambling mecca with high winds that drove the snow sideways and turned the streets into slush.
But the weather didn't keep everyone away. A World Series of Poker tournament drew at least 200 players, and others like Yolanda Cox of Philadelphia arrived before the storm hit.
"We've been here since Thursday," Cox said as she peered into a fitness center that was nearly empty. "We're having fun, so we'll deal with the snow tomorrow."