Officially, the probability is put at 60 percent for the city.
Possible accumulation increases to the north, with an inch possible near Allentown and two inches in the Poconos and northernmost New Jersey.
The more southern and eastern parts of South Jersey might little snow or none at all.
Deep chill. Today's high in the mid 30s might be the warmest temperature for a week.
After an overnight low in the 20s, Tuesday might see a high in the upper 20s and a low in the teens for the first time this winter. Windchills could be in the single digits.
"We're headed for our coldest air since 2011," with temperatures averaging about 15 degrees below normal, Drag said.
Wednesday's high could also be in the upper 20s, with a low around 20. Thursday: High about 30, low about 27. Friday might be back to mid 30s, but Saturday and Sunday should see highs in the low 30s.
"It should warm up early next week," Drag added.
Another snowstorm? "A second and more potent snowstorm may follow for Thursday night and Friday," according to AccuWeather.com. "... The brutal cold at midweek will set the stage for the workweek to end with a snowstorm, one that could bring substantial snow to a larger corridor of the Northeast than the late Monday-Tuesday event."
The computer models vary quite a bit so far, but "it looks like something's going to have to come through," said Drag.
He declined to speculate on the record how much might fall, other than to say, "I think people need to alert that there could be an event that's going to affect travel in the Mid-Atlantic states Friday. There's something coming."
The track of the storm seems likely to mean more snow to the north, but it could take a more southerly track and produce the biggest snowfall of the season in Philadelphia, he said.
That wouldn't take much, though, since before today, the highest total for Philadelphia was 0.7 inches on Jan. 6.
The official forecast puts the odds of precipitation Thursday night and Friday at about 50 percent.
For more on the forecast, go to http://weather.philly.com.
Contact staff writer Peter Mucha at 215-854-4342 or firstname.lastname@example.org.