It’s been a while since we’ve had to talk about severe weather, and today it could threaten the East Coast of all places. A decent cold front pushing toward the coast this afternoon might trigger strong thunderstorms from Nashville to Boston, and some could be severe. Even a few tornadoes are possible in the NYC and Philly areas.
The Storm Prediction Center (SPC) has issued a marginal risk for severe weather—a one on a scale from zero to five—this afternoon, extending from central Tennessee through the Appalachians, over toward the D.C. area and up I-95 through Boston. A marginal risk means that few of the storms that form could produce severe weather (damaging winds, large hail, or a tornado).
Southerly winds streaming toward a developing low pressure system entering New England are dragging warmish and somewhat muggy air up through the eastern states, allowing for just enough instability to form. As the cold front crashes into this unstable air, it will force it to rise and trigger scattered thunderstorms. Some of the storms could form into squall lines along the front, in which case damaging winds (60+ MPH) are possible.
One of the biggest concerns this afternoon is the small chance for tornadoes in the Northeast across parts of Pennsylvania, New Jersey, New York and Connecticut. There could be just enough wind shear in the vicinity of the thunderstorms this afternoon that a few of the storms—especially individual storms that aren’t part of a squall line—could develop rotation, which could lead to a small tornado or two. It’s an outside chance, but the chance is great enough that the SPC included it in their morning update.
The most likely time for severe weather is late this afternoon and early this evening—sooner west, later east.
Even a small, weak tornado is life-threatening if you’re caught in its path. If your location goes under a tornado warning, get to an interior room in the lowest part of the building. The goal of tornado safety is to put as many walls and barriers between you and the outdoors as possible—it’s not the wind that gets you, it’s the speeding debris that causes the problems.
The severe weather forecasts in this post are valid as of 7:54 AM. The SPC releases another forecast update around noon Eastern Time.
Remember that a severe thunderstorm/tornado watch means that conditions are favorable for severe weather, while a warning means that dangerous weather is imminent or occurring right now. You can keep up with severe weather watches by following the Storm Prediction Center, and warnings for individual storms are issued by your local National Weather Service office.
[Simulated Radar: GREarth | Terrible maps I threw together because I’m not on my normal computer: me]