A round of potentially severe thunderstorms is expected to develop late this afternoon and evening across portions of eastern Pennsylvania, New Jersey and northern Delaware, with damaging winds, large hail and a couple of tornadoes possible.
The greatest severe weather threat is expected between roughly 5 PM through early morning Wednesday, although an isolated storm could develop earlier in the afternoon. Additional showers and thunderstorms may linger into the overnight hours, but the severe weather threat should gradually decrease after midnight.
A frontal boundary lifting north of the region will become the focus for thunderstorm development as a disturbance approaches from the Great Lakes. Initial storms are expected to develop near northern New Jersey and northeastern Pennsylvania before additional activity gradually develops farther southwest toward the Lehigh Valley, Philadelphia metro, coastal New Jersey and potentially northern Delaware.
Atmospheric instability will be unusually strong for early September, with MLCAPE potentially reaching 2,000 to more than 3,000 J/kg. Combined with 35 to 45 knots of deep-layer wind shear, the environment will support organized thunderstorms, including supercells, multicell clusters and possibly a few bowing line segments…