Even though it was a “conditional” threat for severe weather, it’s hard to say the storms on Friday, August 10, lived up to their potential across the area. Part of that reason was the very slow movement of the upper level energy and the cold front associated with it. Also, morning rain and an intensifying front-running system (which later slammed New England) helped to stabilize the air.
There was still sufficient potential to motivate myself and meteorologist Mark Ellinwood to attempt a mid-Atlantic storm chase. We left the D.C. area early afternoon and headed northwest towards a zone where instability was building in the wake of morning storms. It was also a bit closer to more favorable upper-level winds (compared to further east).
We initially staged in Frederick, Md. to grab a late lunch and determine our target. At this point radar was mainly quiet, and concerns were growing that storms would not materialize. The main story was increased midday sunshine, helping to build fuel in the atmosphere for possible storms, but ultimately did not help spawn many.
However, ingredients continued to come together at the eastern end of the higher terrain to the west, so we pushed further northwest, eventually to the west of Hagerstown. At the same time, showers — aided by orographic enhancement — started to blossom into thunderstorms over the West Virginia panhandle, western Maryland and into southern Pennsylvania.
We got first sight of a building storm across the border while to the southwest of Clear Spring, Md., right across the river from WV. Within 45 minutes the storm was in Maryland and a severe thunderstorm warning issued. We headed back east to stay in front of it.
While the storm was predominantly outflow dominant (expelling more cold stable air, than ingesting moist, unstable air), there were some signs of rotation particularly early in its life, and the storm exhibited supercell characteristics off and on.