The heaviest snowfall is forecast between 6 a.m. and 6 p.m. Saturday, with the biggest totals in South Jersey and decreasing further inland.
Forecasters expect the precipitation to be "mainly a snow event with mixing along the coast," with two to four inches of snow expected in much of the region, and as much as five inches in South Jersey.
The National Weather Service has set a winter weather advisory for much of the Philadelphia area, including parts of Delaware, Chester, Bucks and Montgomery Counties, for 1 a.m. Saturday until 1 a.m. Sunday.
Parts of South Jersey, including Camden and Cherry Hill and stretching eastward, are under a winter storm watch, with "heavy snow possible" from late Friday until late Saturday, according to the weather service. In Cape May and other spots along the Shore, snow began falling by 3 p.m., and by early evening crews were preparing to deal with it.
"Be prepared for snow-covered roads and limited visibilities, and use caution while driving," the weather service warned.
So what to expect? First, the cold. The weather service forecast Saturday's high to reach 35 degrees with accumulation of two to four inches of snow possible in the city, more in South Jersey and less in the western suburbs. The mercury will dip to 27 degrees overnight, with temperatures expected to rise slightly to highs of close to 40 degrees for Sunday and the start of the workweek.
In the city, the snow, moving from the South, will likely begin after 2 a.m. Saturday.
PennDot began Friday to pretreat some major roadways in anticipation of the winter weather, spokesman Brad Rudolph said.
"It's early, and we're still assessing our game plan," he said.
The snowfall forecast remained in flux, with AccuWeather forecasters saying it may not be time to dust off those snow shovels quite yet.
"It may be a close call with accumulating snow vs. melting snow from New York City to Philadelphia, Baltimore, and Washington, D.C.," AccuWeather senior meteorologist Dave Houk said Friday. "New York City will have a better chance at an inch or two accumulation, since some of the snow will fall during Saturday night."