Most of the region is under a Severe Thunderstorm Watch until 1 AM, with gusty to damaging winds the biggest threat as these storms push south and southeast.
Areas that aren't under the watch include Atlantic, Burlington, Mercer, and Ocean Counties in New Jersey, the Poconos, and points north.
Storms are approaching the Harrisburg area as of 9 PM, pushing east-southeast. These should reach the western suburbs around 10-10:30 PM, with the city likely experiencing storms by 11 PM if they hold together. This line of storms does have a history of producing damaging winds and occasionally some small hail. The trend will be for at least some weakening as the night progresses but given their current intensity a watch being issued does make sense.
More: Current Weather Page (for radar, lightning data, etc.)