- Scattered storms possible this evening, through around 11 p.m.
- Heavy rain and lightning is possible in any storms that form
- Isolated storms may be severe with damaging winds and/or hail
- Most likely timing for storm in the immediate metro area (within one country radius of D.C.) 6-9 p.m.
9:25 p.m. update: What looks to be one last batch of moderate to heavy rains is now working west to east across the metro area. The main cluster of activity with the most lightning is focused from I-66/D.C. toward points south, but scattered showers (some heavy) are tracking east through the northern suburbs as well. These scattered showers and storms should tend to move out of the area from west to east around 11 p.m. to midnight.
Back edge of showers and storms should move out of area from W to E approx 11pm-midnight pic.twitter.com/rhZaIGSF1q
— Capital Weather Gang (@capitalweather) September 1, 2014
8:05 p.m. update: Pockets of heavy rain and dangerous lightning persist, mainly south of I-66 in Prince William and Fairfax counties, and along and south of the Beltway in Prince George’s County. Additional weaker scattered showers and storms are now moving east into Fauquier and Loudoun counties and should track east across much of the area over the next few hours. But we may well be done for the evening with anything of the very strong to severe variety.
7:15 p.m. update: The worst of the weather north and east of town has moved east into the northern half of Anne Arundel County (the southern edge of the activity could clip Annapolis in the next 45 minutes or so. Inside and near the Beltway, no big storm right now, just pockets of moderate to heavy rain.
To the west, we have a steady stream of storminess moving east through central Fauquier, central Prince William, and now extending east into southern Fairfax County. If you are west/southwest of D.C. and south of I-66, expect a rainy/stormy go of it next couple hours.
6:30 p.m. update: The storm in southeast Montgomery County heading off to the northeast towards Greenbelt and Laurel is the most intense.
There is also second area of storms to the southwest which should impact areas that missed this first batch. It stretches from Warrenton to around Centreville and is moving east northeast northeast towards Fairfax and Burke. Basically, along the I-66 corridor in Virginia, expect heavy rain and thunder for the next hour or so.
6:20 p.m. update: Severe thunderstorm warning for southeast Montgomery County, the northern District of Columbia, northern Prince George’s County, and western Anne Arundel County through 7:15 p.m. This includes Adams Morgan, Howard University, Silver Spring, and Hyattsville. Strong storm with heavy rain, lightning, and possibly damaging wind gusts moving through this area.
6:15 p.m. update: Intense storm moving through southern Montgomery County, including the Bethesda, Chevy Chase and Potomac area. Locally damaging wind gusts not out of the question so stay inside. This storm could also impact northwest D.C. to around Takoma Park.
5:45 p.m. update: A severe thunderstorm warning has been issued for southern Montgomery, southeast Loudoun, and northern Fairfax counties until 6:30 p.m. Reston, Great Falls and Potomac are in the path of this storm, which should mostly track north of the District, although the storm could expand south and affect D.C. proper and our southern suburbs between 6 and 7 p.m. Very heavy rain, lightning and strong wind gusts a good bet.
5:10 p.m. update: The storm to watch is currently near Middleburg at the Loudoun-Fauquier County line. It’s moving east-northeast and a severe thunderstorm warning has been issued until 6 p.m. for northern Fauquier, northwest Prince William, and southern Loudoun counties. This includes Ashburn, Brambleton and Dulles for the threat of damaging winds and hail.
Other storms – well north and west of the District (for now) – may contain heavy rain and lightning, but are not severe at the moment.
4:35 p.m. update: Thus far, storms have focused in western and northwest portions of the D.C. region. A line of storms – just through Frederick – spans from northern Loudoun into eastern Frederick counties. These storms, with some gusty winds, lightning, and heavy rain, are headed into western half of Montgomery and Howard counties over the next hour.
There’s also a very strong storm entering northern Fauquier County for which a severe thunderstorm warning has been issued through 5:15 p.m. Watch out for damaging winds and, possibly, some hail with this storm. Seek shelter.
In general, through around 6 p.m., areas inside the Beltway and to the south and southeast should remain storm free, with just a slight (10-20 percent) chance of a pop-up shower/storm. Short term modeling suggests a slight chance of more storms developing or moving into the immediate metro area between 6 and 8 p.m. We’ll see if that materializes (50/50 chance).
In the meantime, it’s hot out there! Reagan National hit at least 96 today- tying for second hottest day of the summer!
Original post, from 2 p.m.
With a rich plume of unstable air and high humidity, the air mass across our region will become moderately unstable this afternoon. This should fuel scattered thunderstorms, and these storms will likely be more organized and longer-lived than typical “pop ups.”
While the lack of a frontal boundary or vigorous upper-air disturbance should preclude widespread strong to severe storms, a few storms or short lines of storms could become strong to severe. The Storm Prediction Center feels that the overall risk is about 15% for damaging wind and hail late this afternoon and evening. The risk of a very isolated, weak tornado is about 2%.
Storms likely initiate over the eastern slopes of the mountains and move toward the D.C. and Baltimore metro areas during the late afternoon and early evening, though some storms may develop out ahead closer to the metro areas. The best chance of storms in the D.C. metro area is from approximately 4 p.m. to midnight.
The greatest threats will be locally damaging wind gusts (60-70 mph) in wet “microbursts” as well as frequent lightning, small hail (dime-size) and brief, torrential downpours that could lead to street and underpass ponding.
We may repeat this same type of pattern tomorrow afternoon, as the mid-Atlantic seems to have returned to mid-summer form, though the coverage of any showers and storms tomorrow looks to be less than today.