Radar & lightning:Latest D.C. area radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

4:58 p.m. update: By and large, all of the storms in the region are sub-severe…although some locally heavy storms are still affecting parts of Prince George’s County and Southern Maryland. These will take another one to two hours to cross Calvert, St. Mary’s and Anne Arundel counties and reach the Bay.

Behind these storms, we don’t expect much so most folks should be in the clear once rain ends. We’ll have a PM Update published around 5:30 p.m. which has an updated forecast for the rest of the evening through tomorrow. We expect the Severe Thunderstorm Watch to be discontinued soon (except for perhaps southern Maryland). This is the last update in this blog post.

4:45 p.m. update: Storms in Montgomery County have weakened a bit, but are still on the strong (not severe) side as they head into Howard County and eventually into Baltimore (next 30-60 minutes). The strongest activity is in Charles County where a severe thunderstorm warning remains in effect. This storm is headed east northeast towards Calvert and southern Anne Arundel County and should reach the Bay in about an hour.

4:30 p.m. update: Severe thunderstorm warning for N. Charles and SW Prince George’s counties until 5:15 p.m.

4:25 p.m. update: Eastern Frederick and northern Montgomery are getting hammered by strong storms producing downpours, gusty winds and even some small hail. This activity is headed generally towards and into Howard County over the next 30 minutes or so. Well to the south, a cluster of strong storms (see warning info below) is now crossing the Potomac and headed towards Charles County.

4:10 p.m. update: Severe thunderstorm warning for central Charles County, southeastern Prince William and eastern Stafford County until 4:45 p.m. Storm near Stafford may produce wind gusts to 60 mph or higher and some small hail. In potential path: Port Tobacco River and La Plata.

4:05 p.m. update: By far, eastern Frederick county and west and northern half of Montgomery county are either experiencing or about to experience the most intense storms. Facebook reader Rob Pond writes: “Worst storm in Ballenger Creek area of Frederick in a longtime! Blew over a heavy table on the deck and it looks like a hurricane outside.” This storm and a separate cell near Poolesville are both headed towards northern Montgomery County. Germantown, Clarksburg, and Damascus may all be impacted.

3:51 p.m. update: Severe thunderstorm warning for southern Frederick, northwest Montgomery and eastern Loudoun counties until 4:30 p.m. Storm may produce 60 mph+ winds. In possible path: Poolesville, Germantown, Gaithersburg.

3:48 p.m. update: Strong winds and even some small hail were reported near Leesburg, and this storm is now moving into western Montgomery County but no severe thunderstorm warning is in effect for this cell at the moment. The other area of strong storms is in southern Fauquier and western Prince William County. These are also not severe at the moment. In between, more garden-variety thundershowers are moving into western Fairfax County. While it’s possible the strongest activity may do a “D.C. Split”, storms sometimes intensity with little notice.

Radar image from 3:40 p.m. shows strongest activity headed north and south of the beltway (RadarScope)
Radar image from 3:40 p.m. shows strongest activity headed north and south of the beltway (RadarScope)

3:30 p.m. update: The strongest storms are currently closing in on Leesburg and in southern Fauquier County headed towards southwest Prince William and northern Stafford county. Gusty winds, lightning and heavy rains are the main hazards with these storms.

3:14 p.m. update: A severe thunderstorm warning has been issued for southern Loudoun County, extreme northwestern Fairfax County, and extreme western Montgomery County until 4 p.m. In this storm’s path: Ashburn, Lansdowne, Herndon. Damaging wind gusts and hail are possible with this storm.

3:10 p.m. update: A severe thunderstorm warning has been issued for much of northern and western Loudoun County, including Leesburg until 3:45 p.m. Damaging winds in excess of 60 mph with this cell, which will also affect Round Hill and Purcellville.

Area covered by severe thunderstorm watch (National Weather Service) Area covered by severe thunderstorm watch (National Weather Service)

Overview: The atmosphere is juiced and storms are organizing to the west, setting the stage for a round of afternoon and evening thunderstorms, a few of which may be severe.

The National Weather Service has issued a severe thunderstorm watch for much of the Washington, D.C. area through 10 p.m. tonight. The watch extends through the Baltimore metro area and northeast into eastern Pennsylvania and most of New Jersey.

By far, the major threat from storms that develop is strong, possibly damaging, winds although a few instances of large hail cannot be ruled out. Other possible hazards include torrential rain and dangerous lightning. The likelihood of tornadoes is low.

The most likely timing for storms is between 3 p.m. and 7 p.m. west of Fairfax and Montgomery counties, 4-8 p.m. within one county of the District (including Fairfax, Montgomery, Prince WIlliam, Prince George’s, and Howard counties), and 5-9 p.m. east of Prince George’s, Charles and Howard counties to the Bay.