The storms were passing into Frederick and Carroll counties about 7 p.m. but were not expected to be severe or warrant storm warnings.
Baltimore Gas and Electric Co. officials are also eyeing the storms as they work to whittle the list of outages across the region. About 675,000 customers lost power at some point during the storm, reduced to 147,000 as of 5 p.m. Tuesday.
BGE officials plan to restore all the outages by some time this weekend, but more storms could set back the efforts, BGE spokesman Rob Gould said.
"Obviously any discussion of a timeline into this weekend is predicated on the weather not harming our effort," Gould said. Storms that came through overnight Sunday into Monday added 12,000 people to the outage list, for example.
The weather service's Storm Prediction Center is expecting conditions favorable for thunderstorm development over two-thirds of the country both Tuesday and Wednesday.
Wednesday storms are harder to predict, the center's forecasters wrote, with a risk of scattered powerful storms across much of the East again. There is uncertainty about those storms that depends on how Tuesday storms play out. Instability is expected in the atmosphere as hot weather remains, but some of that instability could be released in Tuesday storms, according to the storm center's outlook.
The weather service's office for our region, in Sterling, Va., warns of an upper-level disturbance reaching Maryland on Wednesday. Heat is expected to be more intense during the day, feeding potential storms.
AccuWeather severe weather blogger Henry Margusity, meanwhile, expects a risk of heavy thunderstorms across Maryland both Tuesday and Wednesday. High humidity in the air on the east side of the Appalachians could feed storms as they reach the region tonight, bringing gusty winds and lightning, Margusity said.
Even if storms fizzle, many Fourth of July celebrations could be spoiled by rain. Foot's Forecast is predicting showers during morning parades, and then if storms come, they could blow through evening festivities and fireworks shows. The National Weather Service expects a 40 percent chance of rain Wednesday.
Stay alert for storm watches and warnings, and plan outdoor picnics and fireworks accordingly.
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