Radar shows storms from Reisterstown to Reston, closing in on I-95 and the Beltway. The most intense activity is well north of the Beltway and along and north of Interstate 70, where wind gusts could top 50 mph. These areas remain under a severe thunderstorm warning until 5:45 p.m.
The storms, which will shortly arrive arrive along the west side of both the Baltimore and D.C. Beltways, should hit the cities themselves a little before 6 p.m.
5:15 p.m. — Severe thunderstorm watch for region through 9 p.m.
Strong to severe storms in the region have been underway the past 75 minutes in our western areas, but are expected to be a threat for the eastern half of the region through sunset or so, prompting a severe thunderstorm watch. The watch includes a broad area from the District and Baltimore, northeast to Philadelphia and Atlantic City.
5:10 p.m. — Storms moving into Washington’s western suburbs; Beltway arrival around 5:30 p.m. Warning for areas north of the Beltway.
Radar shows the line of storm stretching from near Westminster, Md. through Frederick and Leesburg and extending southwest into Middleburg. It’s sweeping east at 55 mph.
The most intense rain and strongest winds are in Maryland, headed for the area just north of the Beltway, where a severe thunderstorm warning is in effect until 5:45 p.m. It includes Germantown, Rockville and Columbia. Wind gusts in this zone are likely to top 40 mph and might exceed 50 mph.
At their current speed, the line of storms should reach the Beltway by around 5:30 p.m.
4:40 p.m. — Tornado warning in northern Maryland near Mason Dixon line until 5 p.m.
Warning is in effect until 5 p.m. for zone between Emmitsburg and and Thurmont in north central Frederick and northwest Carroll County. The possible tornado could be near Taneytown at 4:50 p.m. It’s racing east at 50 mph.
4:35 p.m. — Severe thunderstorm warning for Leesburg and western Montgomery County until 5:15 p.m.
The strong line of storms pass through northern Maryland has strengthen some into northern Virginia, prompting a severe thunderstorm warning into northern Loudoun County and western Montgomery County until 5:15 p.m. The storms should move into the region around Leesburg close to 5 p.m. Wind gusts of at least 40 mph, possibly topping 50 mph, are possible. The storms are racing east around 55 mph.
4:30 p.m. — Storms approach Frederick, most intense in northern Maryland, while eyeing D.C. metro area by around 5:30 p.m.
Storms are pushing east of Interstate 81 and bearing down on Rt. 15 from Frederick to Leesburg. The northern part of the line, just to the east of Martinsburg and Hagerstown is most intense, where some wind gusts of at least 40 mph and perhaps topping 50 mph are possible. The National Weather Service received a report of a telephone pole and wires down near Hagerstown.
A severe thunderstorm warning has been extended east through Frederick into western Carroll County, for areas generally north of Interstate 70, through 5:15 p.m.
The storms should reach Frederick in the next 15 minutes.
We’re still expecting arrival of the storms near the Beltway after 5 p.m., probably close to 5:30 p.m., based on their current forward progress.
3:55 p.m. — Severe thunderstorm warning for Martinsburg, Hagerstown and Frederick until 4:30 p.m.
Radar shows a squall line approaching the Interstate 81 corridor. In the zone between Martinsburg, Hagerstown and Frederick, it could produce very heavy rain and wind gusts to 50 to 60 mph as it sweeps through over next 35 minutes. It should hit I81 at 4 p.m. and areas around Frederick closer to 4:30 p.m. The line is moving east very fast, at 60 mph, meaning stormy conditions should only last 30 minutes or so.
3:25 p.m. — Line of storms developing in West Virginia to reach Interstate 81 corridor by 4 p.m., immediate D.C. area closer to 5 p.m.
Radar shows a solid line of showers and thunderstorms, capable of producing 40 to 50 mph wind gusts, in eastern West Virginia. They’re moving east at around 40 mph and should reach Interstate 81 by around 4 p.m. At their current pace, they’d reach the Beltway around 5 p.m.
At the moment, no watches and warnings are in effect, but that could change as these storms head east and potentially strengthen.
Overview (posted at 2:15 p.m.)
A powerful line of thunderstorms is likely to sweep through the Washington and Baltimore region late Sunday afternoon. It has the potential to produce strong to damaging wind gusts, hail and even an isolated tornado.
The afternoon storm threat, however, may be somewhat tempered by stubborn cloud layers and lingering rainfall. This is being generated as a warm front continues to push north through the region. Even so, the National Weather Service’s Storm Prediction Center issued a special early afternoon bulletin indicating that a severe thunderstorm or tornado watch is likely (60 percent chance) for the region.
“Severe storms are forecast to develop this afternoon with a risk for damaging wind gusts and a tornado or two,” the bulletin said.
The most likely window for storms in the region is between 4 and 7 p.m., before they shift east of the Chesapeake Bay.
In the wake of the gusty storms, an additional, widespread surge of winds is expected Sunday night into early Monday morning, prompting a wind advisory between 8 p.m. Sunday and 4 a.m. Monday.
It may be that the post-frontal wind surge actually presents the greater severe weather hazard Sunday, given recent soaking rains and treefall susceptibility.
The storms are being generated by the same powerful system that unleashed widespread severe weather in the South and the Tennessee Valley on Saturday and Saturday night, including deadly flash flooding in Nashville.
An elevated risk of severe storms extends all the way from southern Mississippi and Alabama into the New York City area, along a powerful cold front charging toward the East Coast. More than 70 million people could be affected by severe weather.
Storm timing and impacts
Scattered storms will develop east of the mountains during the late afternoon and early evening hours along the advancing cold front. Here’s the approximate time frame for the storm passage:
- Interstate 81 corridor: 3:30 to 5 p.m.
- Route 15 corridor (Frederick/Leesburg/Gainesville) and suburbs west of the Beltway: 4:00 to 5:30 p.m.
- The Beltway and Interstate 95 corridor: 4:30 to 6:30 p.m.
- East of the Beltway to the Bay, including Southern Maryland: 5 to 7 p.m.
The storms will move at a fast clip and should take only 30 to 45 minutes, at most, to pass any location. The coverage of the storms should be scattered to widespread, meaning most, but not all, locations should experience them.
Here’s the likelihood of different storm hazards:
- Wind gusts over 40 mph: high chance (greater than 60 percent); over 50 mph: moderate chance (30 to 50 percent chance); over 60 mph: low chance (10 to 15 percent)
- Small hail: low chance; large hail: very low chance (5 percent or less)
- Heavy downpours: moderate to high chance; flash flooding: low chance
- Lightning: moderate chance
- Tornado: very low chance
Discussion
Even with reduced solar heating, we do not want to rule out any occurrence of strong to severe storms, but we feel they will not be as widespread as our thinking presented Saturday. As of midafternoon, only a few hours remained before the frontal passage, and for any breaks in the overcast conditions to warm the surface and destabilize the lower atmosphere.
The high-resolution models still insist the D.C. region will reach 70 degrees late this afternoon, although this may be overdone given all the clouds.
As the forecast radar above shows, model simulations still develop a narrow line of thunderstorms. This line is being generated right along the front. It is known to be a vigorous front. The purely mechanical lifting along the front (as opposed to the air rising freely because of its buoyancy) may allow any cells to still tap into very intense wind shear and bring down high-momentum air in localized pockets.
After the storms
After the thunderstorms and cold front pass, skies will gradually clear, but temperatures will drop and winds will crank.
They will become sustained from the west at 15 to 25 mph, with gusts to 45 mph Sunday night.
“Gusty winds could blow around unsecured objects,” the Weather Service wrote. “Tree limbs could be blown down and a few power outages may result.”
The strongest winds are expected to occur between about 8 p.m. Sunday and midnight.
Temperatures that rise to near-70 degrees this afternoon will plunge into the 50s after dark and 40s after midnight. Wind chills will dip to near-freezing by Monday morning.
During the day Monday, the winds will ease some but remain a bit gusty (reaching up to 20 to 30 mph), with sunshine and highs in the mid- to upper 50s.
