A renewed severe storm risk this afternoon


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This morning’s storms looked scarier than they actually were in most areas, but a second round this afternoon is likely to pack a meaner punch, especially along and east of I-95.

The most likely end point for the storm threat is around 3-5 p.m. in D.C.’s far western suburbs (Loudoun and Frederick counties) and around 8 to 9 p.m. closer to the Bay. We expect the prime time storm potential around 3 to 8 p.m. in the region from west to east. Scattered showers and thunderstorms are possible before that.

The area remains under an unusual moderate risk of severe weather, with flooding rain, damaging winds, hail, and isolated tornadoes possible.

The National Weather Service Storm Prediction Center places the D.C. area in a moderate risk zone for severe weather.

The National Weather Service Storm Prediction Center places the D.C. area in a moderate risk zone for severe weather.

Along and to the east of the I-95 corridor, the National Weather Service Storm Prediction Center (SPC) indicates there is about a 10 percent chance of a tornado within 25 miles of a point, 15-30 percent chance of large hail, and 45 percent chance of damaging winds.

A frequent question is whether this morning’s storms will squash the potential for strong to severe storms this afternoon. It might make a widespread severe storm threat somewhat more questionable.  Writes the NWS office in Sterling, Va.:

Cloud cover from …. this morning and additional convection developing … will limit amount of surface heating and adds to the uncertainty of the second round of storms this afternoon. Nonetheless…there is still a potential for a significant severe weather episode.

SPC says chances are the atmosphere regroups. It writes:

The moist environment across much of the mid Atlantic coast region still appears likely to become quite unstable by this afternoon…with daytime heating. Coupled with a band of stronger jet level winds…conditions are expected to become conducive to severe storm development.

SPC says initial storm activity, likely developing in the mid-afternoon hours – may be scattered in nature, but could still produce strong wind gusts and large hail.

“A couple of tornadoes also appear possible…particularly across parts of eastern Maryland and the Delmarva peninsula northward into parts of southeastern Pennsylvania and southern New Jersey,” SPC adds.

By late in the afternoon, scattered thunderstorms may coalesce into a more organized line of storms, especially along and/or just east of the I-95 corridor. The radar simulation below, from the high resolution NAM model, suggests such a scenario.

Radar simulation at 4 p.m. from the high resolution NAM model (WeatherBell.com)

Radar simulation at 4 p.m. from the high resolution NAM model (WeatherBell.com)

The bottom line is that the storm system coming through remains very dynamic and, given some fuel (sunshine and rising temperatures are key; link: satellite loop), has the potential to ignite some strong to severe thunderstorms.

It is possible that some, even many, areas do not experience severe storms…especially the further west of the District you go, towards the I-81 corridor.

Thunderstorm forecasting is inexact, but everyone should remained tuned into possible watches and warnings given the volatile setup.

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D.C. area forecast: A sweaty day with serious storm potential