Strong winds that were probably the result of a microburst or weak tornado downed large trees and lifted part of the roof off St. Aloysius Church near Gonzaga College High School and Union Station on Thursday afternoon. At least one other building in the neighborhood has roof damage and cars were crushed by falling trees in a parking lot near Gonzaga College High School.

A severe thunderstorm warning was in effect at the time. We haven’t seen any injury reports.

Storms moved into the D.C. region on Thursday afternoon, knocking down trees and leaving thousands without power. (Twitter @jeremyart)

It’s possible that there was weak rotation in the winds, but unfortunately it wasn’t obvious on radar. It may have been what we call a front-end notch, or a very brief spin-up along the leading edge of a squall line.

Just as likely, this damage was the result of a microburst — something the D.C. area is becoming more and more familiar with. At least three microbursts caused damage in the D.C. metro area in 2016.

Microbursts are strong, downward bursts of air from thunderstorms. When the fast-moving air reaches the ground, it spreads out in all directions, which leads to strong gusts and perhaps damage.

Microbursts can get pretty violent. Wind speeds in microbursts can reach tornado thresholds, although they don’t spin like tornadoes. They can snap trees and power lines and overturn vehicles and mobile homes. They’re also really good at shearing the roofs off buildings.

In this area, they tend to come in the midst of heavy rain and hail, which is what we saw today. In fact, that’s part of the reason a microburst forms — the rain and hail cools the air, which makes it more dense and helps it sink rapidly.

Hail, heavy winds and pouring rain rolled into the Washington region on Thursday afternoon. (The Washington Post)

We have received a few reports of flying debris in the storm. Debris is associated with both tornadoes and microbursts, so unfortunately that’s not evidence in either direction. You can see from this microburst diagram how the wind ends up lofting debris into the air during a microburst.

In any case, we can say this was a very strong storm with pockets of damaging wind. Some areas only saw a few seconds of wind gusts, and others (like Union Station) experienced the strongest gusts inside the Beltway. If the National Weather Service does a damage assessment to determine whether it was a tornado, we will update this post.