Chance of Severe Storms Tomorrow

The Storm Prediction Center has the region under a slight risk for severe weather on Wednesday as the heat wave/heat event that we're currently dealing with comes to an end with the passage of a late day cool front and the weakening of the heat ridge over the Eastern US.    This is another less-than-optimal setup for severe storms in that some parameters are rather impressive while others are screaming against severe storms.

The items for severe are the heat, humidity, and the development of a trough along the eastern edge of the Appalachians thanks to a wind shift line between west winds coming downhill and southwest winds at the surface, as well as temperature differences between the mountains and the lower elevations in Southeastern and South Central Pennsylvania.   That trough develops in the late morning and early afternoon and acts as a focal point for at least scattered afternoon thunderstorms.   These storms, given a fast wind environment aloft, could bring damaging winds and perhaps some hail, as they move east towards the region.   The NAM, below, shows the thunder threat generally between 2 and 5 PM around the region, earliest to the west and northwest and latest across Delaware and South Jersey.   The timing element is generally consistent across all major models -- generally the early and mid afternoon time frame around the region looks the most likely for any thunderstorm development to occur.

What is working against severe is the potential for surface winds to shift westerly a bit sooner and preclude any trough development downstream of the Appalachians.   A west wind is typically not good for severe storm development in our world and even a southwest wind may keep thunderstorm development more scattered and less widespread.   However, with temperatures in the 90's and dewpoints in the 65-68 range there's more than enough heat and humidity to provide the fuel for something to pop.