Capping occurred due to convergence aloft associated with the right rear quad of a mid-level jet and strong dry advection.
The capping appeared to be underdone by the models.
The capping resulted in a very shallow layer of potential instability.
Mid-level lapse rates were weak, and dry air entrainment was significant.
The warm sector was very narrow; storms may not have had enough time to deepen before they became decoupled from the boundary layer.
The stable boundary layer likely inhibited the low-level stretching necessary for tornadogenesis, especially north of the NY / Pa state line.
0-1 km shear was large, but mid-level storm relative winds were unfavorably weak for tornadogenesis.