Update: The National Weather Service cancelled the tornado watch for all counties west of the Chesapeake Bay in Maryland around 8:30 p.m.
The Storm Prediction Center in Norman, Okla., had been eyeing storms that have lumbered through the Plains states this week to reach the East Coast Friday afternoon and evening. In the mid-Atlantic, the "environment is conducive for both damaging winds and a tornado threat."
Conditions could "prove favorable for storms to become organized with the potential for supercells," the forecasters wrote.
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The watch remained in effect for portions of the Eastern Shore.
Meanwhile, a severe thunderstorm warning was issued for southeastern Baltimore County and Baltimore City and northern Anne Arundel until 8:30 p.m. Up to 60 mph winds are possible.
The State Highway Administration cautioned drivers of a potentially treacherous evening commute. Drivers should not attempt to proceed through flooded roadways or around downed wires, officials said. Truckers were urged to be wary of gusty crosswinds on bridges and overpasses.
Wind warnings were in effect on the Bay Bridge, and two-way operations were not expected to be allowed, the Maryland Transportation Authority said via Twitter.
Showers with strong wind gusts were starting to pass into Western Maryland, West Virginia and Virginia early Friday afternoon, according to the National Weather Service's Baltimore/Washington forecast office.
Tornado watches were meanwhile in effect for the Piedmont regions of the Carolinas as of 2 p.m., effective until 9 p.m. A tornado watch for Central Pennsylvania was issued about 4 p.m., through 11 p.m.
In the Baltimore area, humidity was on the rise Friday afternoon, with dew points in the lower 60s and temperatures in the mid-70s.
Forecasters call for virtually 100 percent chances of rain and thunderstorms, with an inch of rainfall possible.