Ah ok! So first read the “Topography” section of another comment I made on this post. There I explain what “Tornado Alley” is and how tornadoes form.

These conditions can technically exist in many places, but North America specifically has the perfect set of conditions. As climate is changing, Tornado Alley has made a sharp shift eastward over the past 100 years. It used to be mostly located over Texas, Oklahoma, Kansas, and Missouri, but has since been pushed to be mostly over Kentucky, Tennessee, Mississippi, Alabama, and Georgia. Likewise, all of the corresponding elements that result in tornadoes have become more prevalent in the surrounding areas, including a few stray systems from the Midwest potentially reaching into Pennsylvania.

Pennsylvania is also in a pretty interesting spot to watch, especially eastern Pennsylvania, because during correct conditions mid-summer through mid-fall, you can get an usually strong and consistent build up of hot, moist air from the coast trapped up against the mountains in the center of the state, and then an overlying cold airmass from up north. When met with atmospheric instability, these can create conditions necessary to spawn tornadoes.