Showers and storms linger overnight

6:40 p.m. -- Rain relents in D.C. metro area for now, but watching line of storms out west

We’re seeing a break in the rain across most of the metro area. There is, however, a broken line of storms out west, currently just getting into western Fauquier and Loudoun counties and stretching all the way south of Charlottesville, that could drift toward our area later this evening. We’ll update in this post as needed.

5:45 p.m. -- Possible area of rotation pushing through Beltway area but no tornado or tornado warning

We’ve been monitoring some rotation in a thunderstorm that tracked from Alexandria through the District and is now approaching north Silver Spring, but the National Weather Service has not deemed it intense enough to issue a tornado warning.

This rotation area did prompt the Virginia Railway Express to hold trains between Springfield and Crystal City and the University of Maryland received a tornado warning from its weather provider, but there is no official tornado from the National Weather Service. VRE and the University of Maryland likely received the warning from a private weather information provider which is not the official source for tornado warnings.

4:50 p.m. -- Heavy rain surges into immediate D.C. area; Tornadoes have been spotted in Richmond

Heavy rain and storms have pushed into the immediate metro area, streaming up from the south along Interstate 95. Lookout for ponding of water on the roads in poor drainage areas.

There are no tornado warnings in effect in immediate area, but there are two in the Richmond area - where multiple warnings for twisters have been issued and tornadoes were confirmed on the ground earlier.

There is no immediate sign of tornado development in the D.C. area but we will continue to monitor.

3:40 p.m. -- Tornado watch issued for Washington region until 10 p.m.

The National Weather Service issued a tornado watch for much of the region until 10 p.m., including all counties and cities except for Montgomery, Loudoun, Howard and Frederick. Conditions are growing more favorable for tornadoes and warnings could be issued at any time. If a tornado warning is issued, take shelter in an interior room, away from windows.

The National Weather Service canceled the tornado warning for the Fredericksburg area and issued a new warning for Brooke, Va., and far southwest Charles County, as the storm tracked northeast.

3:20 p.m. -- Tornado warning for Fredericksburg, Va., area

The National Weather Service issued a tornado warning for parts of Stafford and King George counties in Virginia, including the Fredericksburg area. Rotation was observed on radar which meant a tornado could be present, but had not yet been confirmed.

Original post

The center of Tropical Depression Florence passes to Washington’s west today, and will draw a slug of rain and storms through the region through this afternoon and evening. The rainfall could be locally heavy and enough to cause pockets of flooding.

Because of spin in the atmosphere related to Florence’s remnants, we cannot rule out a brief tornado or two embedded within any thunderstorms that develop this afternoon. Any tornado activity would be isolated but bears watching, especially between about 3 and 6 p.m.

As of around 1:30 p.m. Jeff Halverson, Capital Weather Gang’s severe weather expert, said he was a growing a bit “more concerned” about the tornado potential. Severe thunderstorms have already prompted tornado warnings south and west of Richmond.

The Weather Service’s Storm Prediction Center has placed the region in its marginal risk zone for severe storms.

Although the chance of storms and flooding is highest in our western areas, radar and computer model forecasts suggest heavy storms will affect some of our eastern areas, as well.

The National Weather Service has expanded a flash-flood watch initially issued for the District and areas to the west to include areas east of Interstate 95.

“Average rainfall amounts of 1 to 2 inches are expected, with locally higher amounts likely,” the Weather Service’s flood statement said. “Due to the wet summer, this amount of rain may result in rapid rises of water on creeks and streams as well as urban areas, especially if several intense showers track across the same area.”

If it is raining heavily, avoid routes near creeks and streams, which could overtop their banks quickly. Never try to cross a flooded road in your vehicle — turn around.

Short-range computer models and radar suggest the heaviest rainfall will arrive early this afternoon. By late afternoon, the solid area of rainfall is likely to have shifted to the northeast, but scattered showers and storms may trail behind it, containing brief downpours. After sunset, a few showers and storms may linger into the overnight hours but should be hit-or-miss.

However, another round of showers and storms may swing through Tuesday afternoon and evening with locally heavy rainfall, which could produce more pockets of flooding.

River flooding risk

The heavy rainfall predicted in the mountains to our west (2 to 4 inches or so) as well the rain in the immediate area will raise river levels along the Potomac and Shenandoah rivers.

“[T]he latest model guidance suggests nearly a dozen forecast points on main stem rivers in the Shenandoah and Potomac River basins may flood in the next few days,” the National Weather Service serving the region wrote in its morning discussion.

River flood watches have been posted and include the stretch of the Potomac all the way down to Little Falls affecting shorelines in Loudoun, Montgomery and Fairfax counties. Generally minor flooding is expected.