8:30 p.m. update: As I suspected might happen, these storms weakened as they ran into more stable air over the immediate metro region. And the squall line continues to fragment as it progresses eastward. Over the next 30-60 minutes, some locations along and east of I-95 may see some brief downpours and gusty winds, others may experience no thunderstorm activity. Unless storms re-intensify, this will be the last update this evening. Refer to Ian's PM Update from earlier for forecast details for tomorrow and beyond.
8:00 p.m. update: Storms are now impacting eastern Loudoun and northern Prince William counties and on the doorstep of Fairfax and Montgomery counties. Should move inside the beltway between 8:15 and 8:40 p.m. Storms have weakened and there are no warnings in effect for immediate metro area though warnings are in effect in Prince William and Stafford counties. Despite lack of warning for the immediate metro area, gusty winds and downpours are likely. Here are a couple reports from commenters and Twitter followers who have been impacted:
@megachris dime size hail in Leesburg
@spgass1 eastern warren co ... heard plenty of thunder... and watched trees sway in the wind... power flickered...
7:30 p.m. update: The warnings for the western suburbs detailed in the update below (from 7:00 p.m.) remain in effect as the storms continue advancing towards the immediate metro region. While these storms are not as intense as those from a week ago this past Sunday, trees have been reported down on multiple roads near Winchester, Va. The forward motion of the storms does seem to be slowing a bit, so they may not impact western Fairfax and Montgomery counties until around 8 p.m. moving towards the District between 8:30 and 9 p.m.
7:00 p.m. update: The National Weather Service (NWS) is wasting no time in sounding the alarm bell for these fast moving storms. A Severe Thunderstorm Warning is in effect through 8 p.m. for a large part of the western suburbs (including all of Loudoun and much of Fauquier and Frederick counties) through western parts of both Fairfax and Montgomery counties -- where the storms will arrive closer to between 7:30 and 7:45. NWS is calling this a "dangerous situation" and indicates storms have a history of producing "widespread wind damage"
From 6:00 p.m.: The Storm Prediction Center in Norman, O.K. has issued a Severe Thunderstorm Watch for the entire region through 1 a.m. It highlights the following risks with these storms:
HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING...
A strong thunderstorm squall line currently is ripping through eastern West Virginia into western Virginia at a forward speed of around 55 mph. These storms have a history of producing damaging winds, with a gust of 78 mph reported in Cumberland, Md. While they may lose some of their intensity as the sun goes down, strong to severe storms could impact the metro region between around 7:30 p.m. (in the outer western suburbs) to 10:30 p.m. in the eastern suburbs. Though NWS highlights the possibility of hail, the most likely severe impacts with these storms are strong winds and dangerous lightning. We will post updates as these storms draw closer.