Modeling has sped the timing of the approaching cool front up a fair amount, with Saturday evening and Saturday night looking like the "prime time" for the front's passage. The good news is that Sunday will end up being very nice...the bad news is that Saturday evening will not be.
Showers and storms, some of which will produce steady and heavy rainfall, will work into the Philadelphia metro during the late afternoon and evening hours. Like our discussion yesterday, it does appear the best chances of heaviest rainfall will reside to the city's west and northwest but odds do favor at least a half of an inch of rain in the lion's share of real estate. One inch (or higher) totals have a chance of occurring to the northwest of the city, partly across the Philadelphia suburbs but also up into the Poconos and back across Central Pennsylvania.
As of now, severe weather continues to not look likely but some storms will produce heavy rain.
This should all push through by daybreak Sunday, yielding a progressively nicer day throughout Sunday as high pressure builds back in from the west.