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* Severe thunderstorm watch until 10 p.m. *

6:45 p.m. — Worst of first wave of storms has exited, after producing areas of damage. More storms still possible this evening

The first wave of storms has exited our eastern suburbs and is starting to cross the Chesapeake Bay toward the Delmarva. But it left pockets of damage in its wake, with the area around Manassas hardest hit. Here is a summary of the reports received by the National Weather Service:

  • Hail up to 1-inch in diameter fell around Manassas, and one woman suffered a head injury.
  • Numerous trees were toppled around Manassas.
  • One person was injured from a tree down on a home in Fort Washington (in Prince George’s County).
  • In Gainesville, trees blew down, siding blew off a building and a fence blew over an intersection.
  • Winds gusted up to 53 mph at Reagan National Airport.
  • Multiple reports of downed trees in Alexandria.
  • Trees and wires came down around Winchester.

Here are some photos and videos from the storms and related damage:

This will be our last update in this article. Some more scattered showers and storms are likely this evening through around 11 p.m. Those will be covered in our PM Forecast update, coming out a little after 7 p.m. Find it on the Capital Weather Gang section front.

5:55 p.m. — Intense storms east/southeast of Beltway and near Baltimore pushing toward Bay

Storms have pushed east of Interstate 95 and are clustered in two zones: one in southern Prince George’s County and a second in northern Anne Arundel County into Baltimore. All of this activity will exit over the Chesapeake Bay over the next hour or so. But both of these zones could see storms unleash wind gusts up to 60 mph along with very heavy rain and lightning.

5:15 p.m. — Most intense storms are south and north of District

Radar shows two intense storm cells — splitting off from the District to the south and north. One is near Alexandria extending south of Lorton, pointed at Suitland, Clinton and Waldorf, and the other is just east of Olney, pointed at Laurel. Both will cross Interstate 95 into Washington’s southeast and northeast’s suburbs, respectively. The main hazards with these storms are strong to damaging winds, possibly reaching 60 mph, and small hail, in addition to heavy rain and lightning.

5 p.m. — Report: Head injury from hail reported in Manassas

The National Weather Service reports one woman suffered a head injury due to hail near Manassas according to local emergency management in Prince William County. The agency received reports of hail up to one inch in diameter.

4:55 p.m. — Severe thunderstorm warning for southern half of District and its eastern and southeast suburbs

4:45 p.m. — Damaging storm heading into Fairfax County

A severe thunderstorm warning has been expanded into the southern two-thirds of Fairfax County until 5:15 p.m. as the damaging storm which blew through Manassas heads off to the northeast. It is not quite as intense as it was at peak strength but could still unleash gusts up to 70 mph according to the National Weather Service. The storm is over Clifton and Burke and headed toward Springfield, Alexandria and south Arlington.

Here’s what the storm looked like in Manassas, where the storm reportedly toppled trees:

And here’s a visual of hail from the same storm, which was as large as one inch across according to the Weather Service:

4:30 p.m. — Very Intense storm near Manassas, headed toward Centreville

While storms northwest of Washington have weakened some, an extremely intense cell has popped up near Manassas capable of producing damaging winds and hail. It has prompted a severe thunderstorm warning for much of central Prince William and southwest Fairfax counties until 4:45 p.m.

The Weather Service warned winds up to 80 mph are possible along with golf ball size hail. “This is a very dangerous storm,” it wrote

3:50 p.m. — Strong to severe storms affecting northwest part of region

A broken line of severe storms is affecting the area from the Loudoun-Fauquier county line through Frederick County, Md., where severe thunderstorm warnings are in effect until around 4:15 p.m. The main hazard in these storms is damaging winds, although some small hail is possible. These storms are moving east-northeast and will likely impact western Montgomery, western Howard, and Carroll counties over the next 45 minutes or so.

These storms do have a history of producing wind damage with reports of trees, power lines and traffic lights down near Winchester. The most intense activity is currently pointed at southwest Frederick County.

2:50 p.m. — Severe thunderstorm watch issued until 10 p.m. as storms erupt along Interstate 81 corridor

The National Weather Service has issued a severe thunderstorm watch for the region until 10 p.m. The watch area includes much of Northern Virginia, Maryland, and the District and also expands northeast as far as New York City.

Radar shows numerous storms flaring up along and east of Interstate 81, including severe cells in between Front Royal and Winchester and near Charles Town, W.Va.

A severe thunderstorm watch means conditions are favorable for severe storms but not a guarantee. But where any severe thunderstorm warnings are issued, it means dangerous storms are imminent or occurring and you should seek shelter.

The storms developing near I-81 may affect the immediate metro area between 4 and 6 p.m. but will probably be hit or miss. In addition to heavy rain and lightning, the main risks in the most intense storms will be damaging winds and hail.

Original article from 1 p.m.

Amid today’s hot and humid air over the Washington region, scattered thunderstorms are expected to erupt this afternoon and could linger into the evening. A few of these storms could be severe, unleashing damaging wind gusts and hail.

The storms will be hit or miss but most numerous in the immediate area between about 3 and 6 p.m. After an initial round of storms, some more widely scattered showers and thundershowers could linger into the evening. In other words, while the risk of severe weather is highest through the early evening, we may not be in the clear until late tonight.

The National Weather Service has placed the Washington region in a slight (Level 2 out of 5) risk zone for severe storms.

While not particularly likely, there is an outside chance of a short-lived, isolated tornado among the storms that develop. Similarly, we cannot rule out an instance or two of large hail.

Storm overview

Storm coverage: Scattered (any location in the region has about a 40 percent chance of measurable rain).

Rainfall potential: Highly variable but up to 0.5 to 1.0 inches in the heaviest storms.

Most likely storm window:

  • Interstate 81 (Hagerstown/Winchester/Front Royal): 1 to 4 p.m.
  • Route 15 (Frederick/Leesburg/Gainesville): 2 to 5 p.m.
  • Interstate 95 (Baltimore/Washington/Fredericksburg): 3 to 6 p.m.
  • Route 301 (Crofton/Upper Marlboro/Waldorf): 3:30 to 6:30 p.m.

Storm duration: In areas that get hit, the storms should last 30 to 45 minutes or so. Widely scattered showers and thundershowers could pass through the region after these windows into the evening, but they should be generally not as strong and more spotty.

All clear? After midnight.

Risk of storm hazards:

  • Downpours: Medium-high
  • Lightning: Medium-high
  • Damaging winds: Medium
  • Small hail: Medium
  • Large hail: Low
  • Flash flooding: Low
  • Tornadoes: Low

Discussion

Today’s severe weather potential is predicated on sufficient destabilization (surface heating, which promotes thunderstorm development) and wind shear (increase in winds with altitude, which organizes and intensifies storm cells). The surface forecast chart for 8 p.m. is below.

In this chart, we see a cold front exiting the Great Lakes. That front is not in play as the trigger of today’s storms. Rather, with low-level winds from the south affecting the Appalachians, one or more broken lines of storms will develop along the ridge crests and sweep eastward.

Additionally, an elongated trough of surface low pressure (dashed orange line) east of the high terrain may help force the ascent of air and congeal a broken storm line.

The air mass will be warmer and moister than yesterday, courtesy of winds from the south, with decreasing cloud cover through early afternoon. This will destabilize us to the extent that storm updrafts may become quite vigorous. Values of buoyant energy integrated through the atmosphere are predicted by models to reach 2,500 Joules/kilogram; anything topping 2,000 raises our concern about severe weather prospects.

As for wind shear, the morning weather balloon launch at Washington Dulles International Airport reveals that the wind increase with altitude is 30-to-35 mph through the lowest few miles of atmosphere. That is a threshold value for promoting “upscale” growth of individual storm cells into more organized, long-lived multi-cell clusters and short line segments.

What do the forecast models predict? Our highest-resolution runs suggest that storms will pop over the mountains by mid- to late afternoon and move east. But the coverage is predicted to be spotty, and any line that forms is broken. But those cells are simulated to be fairly intense, enough to perhaps trigger local storm warnings.

Two of these runs, from the HRRR and high-resolution NAM models, are shown below:

Note that while these radar simulations show storms missing parts of the immediate area, they are just projections and cannot peg the exact location of storm hours in advance. They are best for getting a sense of the general storm coverage, timing and direction of motion.

Locally severe cells will be capable of generating intense lightning, torrential rain, hail of up to the size of a quarter and damaging wind gusts in the range of 60 to 70 mph.

CWG staff will be monitoring the situation throughout the afternoon for issuance of any watches and warnings.