After that line of storms passed, the sun peeked through the clouds, but forecasters continued to warn that the day's biggest severe weather risk was to come in the afternoon.

Maryland had been included in an area with a heightened risks for dangerous winds, potentially of 70 mph or greater, as well as hail and tornadoes, but storm forecasters later shifted that area farther south to Tidewater Virginia and North Carolina.

As the storms hit about 4 p.m., MEMA urged workers to remain at work instead of venturing home on the roads. Earlier, Anne Arundel County sent children in their last days of the school year home ahead of the storm, canceling after-school activities.

The afternoon storms spawned multiple tornado warnings, including one after Montgomery Countyfire officials spotted a tornado that damaged the Rockville Ice Arena, said Chris Strong, a Weather Service meteorologist. About 12,000 power outages reported in Montgomery County, the bulk of those reported to Washington-area utility Pepco, according to the utility.

The weather service typically does not consider a tornado confirmed until its staff surveys and evaluates damage, but it will make such a call when a report comes from a reputable source, said the Weather Service's Lee.

The service said Friday it is inspecting potential tornado damage in Howard and Anne Arundel counties, as well as part of St. Mary's County and several areas of Virginia. A report on the damage and any confirmed tornadoes is expected as early as Friday afternoon, or by Monday at the latest, according to a weather service statement.

In Southern Maryland, the Coltons Point area of St. Mary's — where a tornado was confirmed to have touched down Monday — suffered more damage as the storm downed multiple trees. Nearby, baseball-sized hail was reported.

Flooding was also widespread, with 1.3 inches measured at BWI and 1.06 inches at the Inner Harbor. That brings to 5.35 inches the rainfall total at the airport in the week ending Thursday; about 3.5 inches falls in a normal June there.

While summer severe weather outbreaks are common in the region, Lee acknowledged tornado warnings do tend to be issued more often than in years past because of improved technology. The Weather Service's Sterling office has its own state-of-the-art radar system as well as access to Federal Aviation Administrationradar at BWI, Andrews Air Force base and the two Washington-area airports.

After such an active week, the weather is forecast to quiet over the coming days. The cold front that helped spark the storms will bring low temperatures and low humidity for the weekend, with highs in the lower- to mid-80s.

Reuters contributed to this article.