5:15 p.m. update: See our PM Update for our updated, detailed forecast through Thursday: From summer back to spring, overnight: very cool Thursday
3:30 p.m. update: So far, almost all of the storms are developing south and southwest of the District. I’m not convinced this will continue through the evening, but I can say the chance of storms is certainly higher south of town (60 percent) than north of town (40 percent).
A severe thunderstorm warning was just issued for southeast Fauquier County, Stafford County, and southern Prince William County until 4:15 p.m. A storm 6 miles southeast of Warrenton is heading southeast towards Stafford at 20 mph. It is capable of producing hail and winds to 60 mph.
3:00 p.m. update: Severe thunderstorm warning until 3:30 p.m. for central Fauquier County. Storm near Warrenton, capable of producing half-dollar sized hail and 60 mph winds, moving southeast at 20 mph.
2:25 p.m. update: Severe thunderstorm warning until 3 p.m. for southern Prince William, Stafford, and southeast Fauquier counties. Storm southwest of Dale City moving southeast towards Aquia Harbour. Some small hail and wind gusts to 40-60 mph possible in this storm.
From 2:06 p.m.: A backdoor cold front is sliding south and it’s hard to mistake. Just to our north, the mercury has settled into the 50s in New York City, and low 60s in Philadelphia. Meanwhile, it’s near 90 in southeast Virginia.
At the intersection of these contrasting air masses, thunderstorms will fire this afternoon and evening. The most likely timing for storms in the immediate metro area (within a one country radius of the District) is between 4 and 8 p.m., though isolated storms could form earlier. The chance of getting a storm at any particular location is around 50 percent, (compared to 60-70 percent yesterday).
A few isolated storms have already developed to our southwest and we expect storminess to increase as the afternoon wears on. Overall, we think storm coverage will be somewhat less than yesterday and, on balance, storms should not be as intense. Having said that, a few isolated severe storms may form, capable of producing frequent lightning, damaging wind gusts (50-60 mph range) and small hail. The best chance for isolated severe storms is from the District and to the south.
Writes Jeff Halverson, CWG’s severe weather expert:
The setup is similar to yesterday, except there is less shear (or turning winds with altitude to support severe storms) but similar instability (to fuel them). The main storm mode is likely to be widespread thunderstorm cells some strong with isolated pulse severe. Slow-movers and high precipitable water levels mean heavy rainers. Once again, there’s the risk of intense lightning, small hail, and isolated wet microbursts (i.e. strong storm downdrafts that spread out and accelerate when they hit the ground). Storms may try to organize into a west-east line along cold front sagging through Pa. and this could keep activity going into tonight.
Here’s a simulated radar animation of how storms could develop over the next few hours. This is just a model and what happens in the real world will inevitably vary – but it gives a sense of the storm coverage and hit or miss nature:
Stay tuned to the Capital Weather Gang for storm updates, as needed this afternoon and evening.