11 p.m. update: Thunderstorms moving south/southeast through the west suburbs, now mostly confined to Prince William County, have fallen below severe levels and continue to weaken. Some lightning and gusty winds are still possible as the activity rolls through southern Prince William County, just clipping southwest Fairfax and southeast Fauquier counties, during the next hour.
10:05 p.m. update: Storms mostly held off for tonight’s July 4th fesitivities across the area. But now some strong to severe storms are moving south/southeast through the far west suburbs including Fauquier, southern Loudoun and Prince William counties. Damaging winds to 60 mph+ and frequent lightning are possible with these storms.
8:50 p.m. update: While we still have our eyes on storms to the northwest, now in the panhandle of West Virginia, it now seems likely the metro area will remain storm free through the 9-10 p.m. fireworks hour. If the storms to the northwest survive, they would probably be in the D.C. area approximately 10 p.m. to midnight, and may try to stay west of the District.
7 p.m. update: A few storms that were in Frederick County moving southeast toward D.C. have dried up. Currently radar is quiet across the metro area. We still need to watch an area of storms in southwest Pennsylvania about to move into Western Maryland. They are a couple hours away but it’s uncertain whether they’ll survive.
5:30 p.m. update: A few storms have fired up across the area, and there continues to the be threat of isolated severe weather with any storms that form. Additionally, highs that made it into the mid-90s to near 100 have helped this become one of the hottest Independence Day’s in the last decade and on record. More thunderstorm development is possible through the evening, some of which may produce damaging winds and hail.
From 1:20 p.m.: Temperatures have climbed into the 90s and humidity levels are moderate-to-high (dew points upper 60s). The atmosphere is fueled up for possible strong late afternoon and evening thunderstorms.
Storm timing: Based on analysis of radar and models, the most likely timing for storms is in the 5-10 p.m. window - with areas west of I-95 most likely to be affected during the first half of the window and locations east of I-95 during the second half. It’s not out of the question fireworks at the D.C. mall are impacted. Also note, isolated storms could begin popping from 3-5 p.m., especially well west of D.C. towards the mountains.
Storm coverage and likelihood: There may be a line of storms that come through or they may be more scattered and hit and miss. I’d place overall odds that a storm will affect a given location at slightly better than 50 percent.
Intensity: Any storms that develop will likely contain heavy downpours and dangerous lightning. Damaging winds and hail are a slight possibility. The storm’s intensity may be similar to last night with some potential to be a little stronger. They should not have the same widespread destructive potential as the June 29 derec ho.
Temperatures: Remember, a heat advisory remains in effect through 9 p.m. Temperatures this afternoon reach the mid-to-upper 90s with heat indices of 100-105. Not until around 8 p.m. or a storm comes through, will temperatures drop back into the 80s, whichever comes first. Please hydrate and try to stay cool if spending long periods outside.
Next update: Should storms threaten and/or watches/warnings issued, we will do a new blog post (if there are no storms, we will not). If you are mobile, you can also track our updates on Twitter and Facebook. See also Dan Stillman’s full forecast through the weekend.