Update, Noon: Scattered storms have started to fire up throughout the region, most numerous in Central and North Jersey and in Bucks County as of Midday. More scattered storms will fire up through the course of the afternoon, continuing into the evening hours. Gusty winds and some hail are possible in the strongest of storms. However, because of the slow-moving nature of today's storms heavy rainfall and localized flooding are also possible around the region in places that get any thunderstorm development. Not everyone gets a storm today -- some will get storms two or more times.
The region is under a slight risk of severe weather today -- product of a mid level disturbance approaching the region from the northwest and a frontal boundary stalled nearby. This duo is acting as a trigger for thunderstorm development across the Northeast today (see the radar below for an early morning sampling of what's going on), with the potential for gusty winds and perhaps some hail in the strongest of storms later on. Currently, the most active precipitation areas are across Upstate New York but there are pockets of showers and storms across Western and Central Pennsylvania as well. These will move east through the course of the day -- while the morning activity may not survive through the day, more thunderstorm development will take place this afternoon.
This is the high-res NAM as depicted through StormVista's model maps for 5 PM today. Thunderstorms are shown scattered through Pennsylvania and New York, with a slow general eastward movement with thunderstorms expected as the mid level disturbance is expected to be overhead by late in the afternoon.
Timing-wise, Berks and Lancaster should start seeing storms by mid afternoon, the suburbs between 4 and 6 PM, and New Jersey after 5 PM, with the South Jersey Shore last, mainly after 7 PM. Given that storm development will be scattered and not widespread, some spots will avoid thunder while others could see two or three rounds of thunder this afternoon and evening. With the potential for heavy rain thanks to abundant moisture in the atmosphere, some spots could see an inch or more of rainfall...while others miss the boat on much rainfall of substance.
You can track the storms' progress through the day on our current weather page.