Much of the Delaware Valley will be under the gun, for strong to possibly Severe Thunderstorms later Sunday into Sunday night. A trough of low pressure, along with a piece of Upper level energy (PV) will be moving through the area tonight.
Showers and Thunderstorms will develop this afternoon and continue into tonight. Some of these thunderstorms will contain strong damaging winds, dangerous cloud to ground Lightning, and some small hail.
A severe thunderstorm watch may be issued for parts of the Delaware Valley this afternoon and evening. I'll update later if these conditions materialize into a Severe threat. The biggest threat for severe weather will be over Extreme SE PA, DE and Southern NJ. The remainder of Eastern PA and NJ will likely see strong storms, with more of an isolated threat of any severe weather.
Temps will reach near 70 and more sunshine can be expected during the morning hours, before the clouds and precip moves in during the afternoon. The atmosphere will become quite unstable quickly, as temps rise during the day, and cooler air a loft, from our Upper Level low moves in. This will be the trigger mechanism for the strong storms and possible severe threat into tonight.
Once again we have another cold core, closed H5 low in the picture. This PV will be further north than the last one that moved into the northern M/A States, producing the heavy rain event. This latest PV will move across SE Canada and into New England later tonight. Vort max energy will be stretched out into the M/A states as a trough line from this H5 low. Instability and convection will increase ahead of, and along this boundary, as the system approaches tonight.