Weather watchers have upgraded Central Maryland's chances of thunderstorm activity Wednesday night during prime firework show hours.
The Storm Prediction Center in Norman, Okla., gives an area from the Great Lakes to the Chesapeake Bay a "slight" chance of severe weather tonight, a rating that is second on a four-level scale of risk. A thunderstorm watch was issued at 4:25 p.m. until 10 p.m. for a swath of West Virginia and Ohio that includes Garrett County.
Some isolated storms propped up in Frederick County about 5 p.m.
A heat advisory is in effect for most of the Baltimore area for the Fourth of July, with heat index values rising to 100 to 105 degrees potentially feeding afternoon storms.
Harford, Baltimore, Howard and Anne Arundel counties and Baltimore City are part of the heat advisory, issued by the National Weather Service. It will likely be an eighth day with highs in the 90s in the Baltimore area.
Storm chances remain nebulous but real. The Storm Prediction Center in Norman, Okla., predicts disorganized storm systems east of the Mississippi creating scattered storms. Their severity will depend on heat conditions, the forecasters say, and with a lot of hot, humid air over Baltimore, that could mean some bad weather for fireworks shows.
The National Weather Service's Sterling, Va., office predicted a 50 percent chance of rain and a high of 98 degrees in Baltimore in its Wednesday forecast.
AccuWeather severe weather blogger Henry Margusity includes Maryland in a swath of the northeast facing the potential of heavy thunderstorms, while Foot's Forecast is calling for the best chance of isolated severe storms between 2 p.m. and 6 p.m.
Any storms that strike could disrupt Baltimore Gas and Electric Co. efforts to restore power, utility officials warned. There were 100,000 BGE customers without power as of 9 a.m. Wednesday, most of them in Baltimore and Baltimore County.