A variety of high-impact severe storms are expected to unfold in portions of the eastern United States today, with tornadic thunderstorms and storms with damaging to destructive wind gusts and even large hail expected to hit parts of Pennsylvania, New Jersey, Delaware, Maryland, and surrounding areas this afternoon. According to the National Weather Service, the peak of the severe conditions should arrive between 2 pm and 9 pm today.
According to the National Weather Service’s Storm Prediction Center (SPC), numerous severe thunderstorms are expected across a broad region from the Tennessee and Ohio Valleys to the Mid-Atlantic and Northeast States today into tonight. Swaths of damaging wind gusts are expected to be the most common impact, but some tornadoes are possible as well. The SPC says more than 37 million Americans are at risk of damaging or destructive winds over an area stretching from Kentucky to New Jersey.
The SPC says that recent satellite imagery reveals a shortwave trough moving quickly southeastward across the Upper Great Lakes region, embedded within the upper troughing that covers much of eastern Canada and extends down into the Ohio Valley. Showers and thunderstorms are already ongoing downstream of this shortwave, with the highest coverage along and near the pre-frontal trough in Ohio. Recent surface analysis reveals a somewhat complex boundary structure, with a wavy warm front, a diffuse pre-frontal trough, and a cold front. The primary warm front appears to extend west-to-east from southeast Ohio across southern Pennsylvania and into northern New Jersey, far southern New York, and extreme southwest Connecticut. The cold front arcs southwestward from northern Lower Michigan through central Illinois and central Michigan.
The SPC says that the highest overall coverage of storms is anticipated along and ahead of the cold front this afternoon through this evening, with additional development expected farther east from central Pennsylvania into central Virginia along the lee trough as well. Highest buoyancy is expected along the western periphery of the cold front from central into western Kentucky, where mid to upper 70s dewpoints are anticipated amid temperatures in the upper 80s/low 90s. Strong buoyancy is still anticipated across Ohio as well. Based on these conditions, robust thunderstorm development is expected along the front. Vertical shear is robust enough for supercells, but linear forcing along the front and strong downdraft production will likely lead to quick upscale growth. According to the SPC, damaging gusts with speeds from 55 to 70 mph will be the primary risk, with brief tornadoes as a secondary threat, and large hail tertiary.
Farther east, a similar convective environment exists, although with slightly less buoyancy and deep-layer vertical shear. A more outflow-dominant multicell mode is anticipated across the central Virginia vicinity, with a trend towards a more organized mode possible with northern extent. Primary risk will be damaging or destructive wind gusts, including a few around 65 to 70 mph. A somewhat confined corridor of greater tornado potential exists from the Hudson Valley vicinity into western Massachusetts/Connecticut as the warm front lifts northward. Here, enhanced vorticity along the boundary coupled with stronger low-level southerly flow could support a few brief tornadoes.
