Snow: How soon, how much, how long?

Revise those earlier expectations. This afternoon, the National Weather Service was calling for about a foot of snow in Philadelphia. As of about 7 p.m., the call was for about a foot and a half, according to the latest snow accumulation map.

The light snow falling in early evening in the Philadelphia area was giving little hint of what was to come.

Winds and the snowfall will pick up, and temperatures will drop, as the system delivers most of its wallop overnight, with snow at times falling an inch or two an hour.

As of 5 p.m., the snow had reached Wilmington, after starting as light snow around noon in Baltimore and Washington, D.C. - cities that might get two feet of snow, according to the National Weather Service.

"It's right there on our doorstep," said NWS meteorologist Lee Robertson at 5 p.m. "Within the next hour it should be moving into the Philadelphia area."

And it did.

By Saturday afternoon, 12 to 20 inches is expected to blanket the Philadelphia area, including western South Jersey and Northern Delaware, according to the National Weather Service.

A map of projected accumulations ran from about 10 inches in Bucks County to a foot and half in Philadelphia to 20 in Camden and Gloucester Counties to about 24 in Cape May County.

Coastal counties in New Jersey, as well as lower Delaware and Maryland's Eastern Shore, face not only lots of snow but possible blizzard conditions with gusts of up to 50 m.p.h. possible between 4 p.m. today to 7 p.m. tomorrow, according to the weather service.

Tomorrow morning, people in the Philadelphia area should wake to lots of snow on the ground, with new snow and old snow being blown around, diminishing visibility for drivers, according to AccuWeather meteorologist Tom Kines.

The snow should be a light powder, easy for snow blowers, bad for snowmen.

Accumulation should continue till early afternoon throughout the region, but winds could continue to stir things up into tomorrow evening, Kines said.

"I think by noon tomorrow, 90 percent of the accumulating snow is done," he said.

The snow will stick around for days, as temperatures remain below freezing into Tuesday, when another significant storm is expected.

It looks like another nor'easter, potentially bringing more moisture from the Gulf of Mexico to meet up with Atlantic moisture, Kines said.

"It could be another six-incher," he said.

Whether the path would include Philadelphia is too early to predict.

For more on the forecast, go to http://go.philly.com/weather.