9:30 p.m. update — Evening storms haven’t materialized, but a round possible toward morning
Evening showers were very scattered and significant thunderstorms never really developed. Radar and short-range models suggest a continued pause in storm activity for the next several hours. However, toward the predawn hours, an area of showers and storms may pass through the area from northwest to southeast. That activity should exit by 8 or 9 a.m., with partly sunny skies developing and warm afternoon temperatures from 75 to 80.
Quick update at 11 p.m.: A few isolated storm cells have popped up in the region, producing some brief downpours and even small hail. The storms are rapidly moving off to the east and southeast toward the Chesapeake Bay before the next likely round developing in the predawn hours.
Updated forecast, 4:30 p.m. — This evening’s storm risk likely highest in southern half of D.C. region. More showers and storms possible toward Wednesday morning.
The wave of afternoon showers and storms has passed except right along the Bay and in Southern Maryland, where locally heavy storms with pockets of damaging winds are possible for the next 30 minutes.
Behind this wave, there is the chance for some more scattered showers and storms this evening, especially south of the District. Forecast models suggest a few intense storms could fire up between around sunset and midnight, but these are unlikely to be widespread. The National Weather Service Storm Prediction Center wrote environmental conditions may be favorable for some severe storms with damaging winds and hail, mainly south of the District, so we will continue to monitor and post updates if needed.
After midnight, we may also see showers and storms approach and pass in the predawn hours through sunrise. They should be diminishing as they pass, but may produce some downpours and a few claps of thunder. Lows end up settling across the 50s.
On Wednesday, some early morning showers could linger, but then we’re looking at a nice and warm afternoon, with partly sunny skies, a steady breeze, and highs 75 to 80.
Original article from 11:00 a.m.
Multiple rounds of strong to locally severe thunderstorms are possible across the Washington region Tuesday afternoon and overnight into Wednesday, with damaging winds and large hail possible where storms occur.
A few scattered storms will be possible late Tuesday afternoon, with second and third, possibly more potent, rounds occurring during the evening and after dark.
Some more showers and storms could pass Wednesday morning, but probably will be somewhat less intense.
Stay weather aware through and be sure to have a way to be notified if any storm warnings are issued for your location.
Storm snapshot: Most likely timing: 3 p.m. to midnight, in two or three waves | Storm duration: generally under 45 minutes | Storm movement: northwest to southeast | Likely impacts: downpours, gusty winds (30 to 49 mph) | Possible impacts: damaging winds (50+ mph), small hail | Very small chance of: large hail | Rainfall forecast: 0.25 to 0.5 inches, with locally heavier amounts
The National Weather Service Storm Prediction Center has placed the entire Washington and Baltimore region in a slight risk zone (Level 2 out of 5) for severe weather.
Damaging winds and large hail are the main hazards with any storms that form.
There is a signal that a couple of storms could tap into strong wind energy at the mid-levels of the atmosphere, which could bolster the hail risk. It’s not out of the question that one or two areas see hail approaching ping-pong ball size.
Areas most impacted
While severe weather is possible over the entire area, that risk will decrease some to the north and east of the Potomac River. According to the National Weather Service, “the best area for storms looks to the area south of Interstate 270 and north of Charlottesville.”
The focal mechanism for storms Tuesday afternoon and evening stems from a warm front draped across the area. The stalled front demarcates the boundary between two opposing air masses, the resulting clash between them sufficient to favor strong to severe weather.
“Much of the uncertainty hinges on the exact position of the front during the afternoon,” explained CWG’s severe weather expert, Jeff Halverson. “D.C. may well be the dividing line between stronger thunderstorm activity to the south and more general showers [and thunderstorms] to the north.”
Skies will continue to brighten beneath patchwork high cloud cover, allowing temperatures to climb into the lower 70s in most spots Tuesday afternoon. Towering clouds will bubble up over the mountains or high terrain in Northern Virginia and the panhandle of Maryland shortly after noon, with a shower or thunderstorm possible there. One or two storms may travel toward the Chesapeake, but are likely to stay for the most part south and west of the Potomac.
“How intense these storms get depends on the amount of sunshine and destabilization of the air mass,” wrote Halverson. “That will likely be stronger south of the warm front into northern and central Virginia, and weaker to the north.”
Halverson wrote that several models brought temperatures in the 70s far enough north to reach D.C., increasing the risk in our local zones. “Today essentially becomes an exercise in monitoring the exact location of the frontal boundary through the day,” he wrote.
More thunderstorm activity will develop by early this evening to our northwest, sagging south and east across our area and increasing in areal coverage and intensity. These storms will continue to sustain themselves even after the sun has set, and may actually achieve peak strength shortly after sunset.
One interesting element of Tuesday’s storms is that some may be “elevated,” or rooted in a layer of warmer air a few thousand feet above a slightly cooler surface. That could enhance the hail risk, and also amplify the sound of any thunder.
An additional band of showers and thunderstorms, probably below severe intensity, could drop south across the area around daybreak Wednesday, accompanying a cold front.
Previous storm updates, which have expired
3:40 p.m. — Showers and storms pushing east of Interstate 95. Severe storm just north of Fredericksburg.
Showers continue pushing through the Beltway area are now crossing the Potomac River into our eastern suburbs.
The most intense activity, including a severe thunderstorm, is south of the Beltway. A severe thunderstorm warning is in effect for the area around Fredericksburg and to its east over parts of Virginia’s northern neck through 4:15 p.m. Radar indicates this storm could produce wind gusts to 50 to 60 mph.
We’ll post a new update at 4:15 p.m. which updates the forecast through this evening, when more showers and storms are possible.
3:10 p.m. — Showers and storms approaching Beltway area. Some heavy activity to west and southwest.
Showers and some heavy thunderstorms are approaching the Beltway from the west, headed east and southeast. The heaviest activity is generally south of Reston and along the Interstate 66 corridor in Virginia west of the Beltway between Bull Run and Oakton through Centreville and Fairfax.
As these storms push east and southeast, heavy downpours, gusty winds, and some lightning are possible especially from downtown Washington and points south, including around Falls Church, Alexandria, Dale City, Mt. Vernon, and eventually across the river into southern Prince George’s and Charles counties, by around 3:30 to 4:00 p.m.
None of this activity is considered severe but some strong wind gusts up to 40 to 45 mph are possible in the strongest activity.
We’re still tracking the possibility of more storms later this evening, after sunset, but this activity may be pretty scattered or hit or miss. Additional information below.
1:25 p.m. — Initial area of rain approaching from northwest, but is not particularly intense
The first wave of showers riding along the warm front draped over our region should arrive between 2 and 4 p.m. from northwest to southeast. This activity is not particularly intense and mainly consists of just light to moderate rain showers, and a few pockets of heavier downpours. It may intensify a little as it moves over the region, and we can’t rule out a bit of thunder, but we don’t expect widespread severe weather from it.
It’s still likely another wave or two of activity may develop toward and after sunset. Associated storms may be a bit more vigorous with a better chance of producing thunder, strong winds, and possibly hail. However, the rain from this first wave may cool the atmosphere and reduce the instability or “juice” for whatever comes along our way this evening. We’ll continue to monitor.