A bout of heavy rain is expected to drench the region throughout the day on Friday bringing the potential for flash flooding in some neighborhoods.
A First Alert has been declared for Friday by the NBC10 First Alert Weather Team -- aimed at making sure viewers are prepared for the severe weather.
NBC10 First Alert Chief Meteorologist Glenn "Hurricane" Schwartz said the large line of storms is moving from south to north and with that track comes the concern of "training." With training, storm would stop moving east to west, but continue moving south to north continually hitting the same areas with heavy rain.
"So if it all moves up [only from north to south]...one area gets pounded, while other areas don't get much at all," Hurricane said.
NBC10 First Alert Weather computer rainfall models are predicting between a half inch of rain in Philadelphia to more than 1.5 inches of rain in Allentown over the course of the storm. Areas to the north are expected to get the most rainfall.
Hurricane says the rain should start arriving in the area by 7 a.m. and could stay until midnight on Saturday should the front move slowly. Thunderstorms could also be embedded in the storm front.
The potential for such heavy rain over that period of time has prompted the National Weather Service to issue a Flash Flood Watch lasting through Friday night for much of the region.
Stay with NBC10 First Alert Weather and NBC10.com for the latest on this severe storm.