An intense storm system could bring widespread and severe thunderstorms to the D.C. region on Monday, capable of producing violent wind gusts, hail and tornadoes in addition to torrential rain and lightning.
The National Weather Service has declared a rare Level 4 out of 5, or “moderate,” storm risk, meaning severe storms that are expected to be widespread. This is the first instance of this risk level in more than two years.
The storms’ timing still needs to be pinned down, but they are most probable between about 1 and 7 p.m. Monday, when an organized and violent squall line is expected to pass. That said, widely scattered showers and storms, some of which could be intense, are possible before this window, as early as 9 or 10 a.m. Rain is expected to linger after the most intense storms pass in the evening.
The fast-moving storms along the squall line and possible hurricane-force wind gusts could topple trees and power lines, leading to outages. Expect travel disruptions and flight delays and avoid driving when the worst storms are passing.
After the thunderstorm threat wanes in the evening, temperatures will tumble and winds will howl, not unlike they did after the strong cold front that swept the region on Wednesday and Thursday. It’s possible that rain on the backside of the front briefly changes to snow before ending Monday night, especially in colder areas west and northwest of the Beltway. Temperatures are poised to fall from around 70 on Monday afternoon into the 30s late at night. Snow accumulation is not anticipated, however.
The storm system inciting this wild weather is the same one that has brought blizzard conditions from South Dakota to the northern Great Lakesand that is expected to ignite severe thunderstorms from the Gulf Coast to Lower Michigan on Sunday.
How the storm may unfold
Mild and humid air will stream northward ahead of the cold front, with very strong winds at all levels aloft. In this type of setting, we expect the impacts to be fairly widespread, with models showing the development of a potent, fast-moving thunderstorm squall line that will form over the mountains and race rapidly eastward, probably between the midafternoon and early evening.
A few severe storms could form ahead of the line between the morning and midafternoon, and could produce a tornado or two, especially south and east of D.C.
Along the squall line, corridors of damaging wind gusts, where the line bows outward, have the potential to reach significant levels. Peak gusts could reach 70 to 80 mph.
Additionally, a few tornadoes could develop in any storms that form along the squall’s leading edge. Squall-line tornadoes tend to be weaker and short-lived but pop up quickly, often with little warning.
One potential limiting factor will be a stubborn cooler layer of air wedged east of the Blue Ridge, with cloud and showers hanging around into the morning on Monday. A strong surge of milder air from the south, and clearing skies, will be needed to scour out this stable layer to fuel intense storms. While the models indicate this will happen, those same models very often are too aggressive in pushing the cool air out. So this remains a wild card in the forecast.
The models also indicate a more unstable air mass, with more storm fuel, to the south of D.C., over central and southern Virginia. It’s here that rotating, long-lived thunderstorms called supercells are more likely to develop ahead of the squall line, with the potential for stronger tornadoes.
How to prepare
Because of the severe wind threat, heightened vigilance and knowing your environment are key to safety. Here are some tips to prepare:
- Secure or bring loose outdoor items inside.
- Charge your electronic devices, given the possibility of power outages.
- Avoid driving during the storms, especially along tree-lined streets. Delay any errands or commuting until the worst of the storms pass. Be aware that downed trees could block routes after the storm.
- For residents with large trees on or near your property, try to park your cars away from the trees and, as the storms pass, move to the lowest floor and stay away from windows.
Severe thunderstorm and tornado watches may be issued Monday morning or early afternoon. Remember that watches mean there is potential for severe weather and that you should stay alert.
If severe thunderstorm or tornado warnings are issued, that means a dangerous storm is imminent and you should seek shelter immediately. In the case of a tornado warning, go to the lowest level of a strong building and shelter in an interior room, away from windows.
Stay close to your cellphone for wireless emergency alerts, which will sound for tornado warnings or violent thunderstorms.
Tornadoes that form in squall lines tend to develop very rapidly, without much lead time, so seconds count when taking shelter.
You should have multiple ways of receiving warnings. In addition to your phone, a NOAA Weather Radio station is a great resource for the latest information.
How unusual this setup is
March is somewhat early for notable severe weather in the D.C. area, although there is at least a small chance by mid-month in most years. The region’s primary thunderstorm season runs from May through September. But storms near the edges of the season — or even earlier — can still pack a punch because the cool-season jet stream is typically stronger than it is in late spring and summer across the Mid-Atlantic.
D.C. averages about a dozen severe storm outlooks per year from the Weather Service’s Storm Prediction Center that are issued the day before potential storms. That number rises to around 20 outlooks on the day storms are expected. Most are marginal or slight risks (Levels 1-2 of 5), with a handful reaching enhanced risk (Level 3). A Level 4 risk occurs less than once every other year on average.
The last Level 4 risk for the area was Aug. 7, 2023. It included a 45 percent risk of damaging wind and a 10 percent tornado risk. The event produced widespread wind damage in the region.
The most recent time a moderate risk was issued the day before the event was June 12, 2013, ahead of storms on June 13. This was before tornado probabilities were included in Day 2 outlooks — an option added in 2020.
Another notable case was during the June 1, 2012, tornado outbreak, when a 15 percent hatched tornado risk briefly covered a small portion of the Mid-Atlantic, including the D.C. area. That level of tornado probability is extremely unusual here and typically signals the potential for significant tornadoes in other parts of the country.
There are cases with heightened severe weather risk that do not come together, although they are increasingly less frequent as forecasting skill improves.
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