Update, 5:55 PM: Now up to 5.95" of rain at the Airport, second rainiest day on record for Philadelphia. One end of the city has picked up nearly six inches of rain -- the other has picked up JUST 0.24" (Northeast Philly Airport). Gotta tell ya that it's pretty remarkable what's going on this afternoon with these thunderstorms. More on this in a little while.
Update, 5 PM: 4.38" of rain as of 5 PM -- second wettest July day on record, all of it falling in two hours' time. You can see the radar shot below showing the rainfall in the 4 PM hour (1.82") along and just east of the river, indicative of that classic "training" scenario where rains just drop over the same areas for hours at a time. Route 42 in South Jersey has flooding, as do the ramps to and from 95 at Broad Street. If you're in the city or points east, be careful over the next couple of hours as these storms slowly work through.
Update, 4:30 PM: Prolific rains falling across South Jersey...earlier across Philadelphia where the Airport has picked up nearly four inches of rain 90 minutes time. This is the view from a few minutes ago along 42 as the Shore crowd tries to come back home after the weekend.
Heaviest rains are across Cherry Hill southwest through Woodbury and down to near Wilmington. These storms are 'training' or taking the same generic track (northeast) as the line slowly shifts east. Training leads to prolific rainfall in short periods of time...such as the four inches of rain in 90 minutes at the Airport.
This line of extremely heavy rain will push east and northeast slowly over the next few hours, with the bulk of the heavy rainfall now centered across South Jersey and eventually into Central New Jersey as these move on through.
Scattered lines of thunderstorms are firing up across the region, producing near two inch rainfall rates across parts of the region and also localized downburst of gusty winds within some of the thunderstorms as well.
Storm movement is north-northeast and northeast at a pretty good clip but because the lines aren't moving all too quickly eastward the individuals that fire up can produce a hefty amount of rainfall in a short amount of time. Gilbertsville picked up 1.33" of rain in about 45 minutes of time earlier this afternoon. A second storm near Wilmington warranted a severe storm warning earlier as it showed signs of producing 50-60 mph winds. Such storms will be the exception but are possible in spots.
Storms will be scattered around in lines, meaning some spots miss and others get hit...perhaps more than once. The city in particular will get in on thunderstorms over the next hour with the batch near Wilmington, with the batch across Chester County perhaps pushing in after 5 or 6 PM.
More: Current Weather Page