A severe thunderstorm dumped so much rain on the city late this afternoon that people standing Downtown temporarily lost sight of Mount Washington.
A severe thunderstorm warning for much of Western Pennsylvania expired at 7:15 p.m., but a thunderstorm watch will remain in effect until 10 p.m., according to the National Weather Service.
Meteorologists have also issued a flash flood watch and said they expected the storm to bring damaging winds and large hail.
This afternoon's thunderstorms dumped as much as an inch of water in some places, including Clarion, in about a half-hour, said National Weather Service meteorologist Rich Kane.
Another wave of thunderstorms, currently near Columbus, Ohio, is moving east at about 40 mmph. Mr. Kane said he expected the storm, which is "packing winds," should hit the Pittsburgh area between 6:30 and 6:45 p.m.
Reports that a tornado might have touched down in Jefferson County this afternoon are unconfirmed, Mr. Kane said. He said meteorologists, who have been communicating with emergency officials in various counties, have reported numerous trees down and damage to some houses, but nothing indicative of a tornado.
Lee Hendricks, another Pittsburgh meteorologist, said the predominant threat this afternoon is heavy wind. He said thunderstorms are moving quickly east and bringing with them strong winds.
Joey Vallarian, a spokesman for Duquesne Light, said in a statement that about 5,100 people in the region lost power when this afternoon's storms rolled through. About 2,550 people remained without power shortly before 9 p.m. He said He said crews were currently working to assess damage and repair downed lines throughout Pittsburgh. He did not yet know when power might be restored to those who lost service.
Because of the possible storm, Pittsburgh pools closed at 2 p.m. today and the Mayor's Big League games scheduled for this evening were canceled.
"We urge residents to err on the side of caution, stay indoors, and check on your elderly neighbors and family," Pittsburgh Mayor Luke Ravenstahl said in a statement. "As always, stay tuned to local media and your national weather radio for new developments."
The city's public safety and public works departments have put extra workers on duty, and the departments have moved equipment to possible trouble spots. The city deployed swift-water rescue teams last week during flash floods in Overbrook and Hays.
"Residents must use extreme caution, especially during their rush hour commute," Pittsburgh public safety director Michael Huss said. "Do not drive into flooded water, and look out for downed trees and power lines."
PennDOT said workers were monitoring road conditions, especially near streams and creeks on secondary and rural roads.
This morning, the weather service issued a heat advisory for most of Ohio, northern West Virginia and southwestern Pennsylvania from noon through 8 p.m. Air temperatures will reach into mid 90s with heat indices to about 102.
The weather service said the combination of hot temperatures and high humidity will create a situation in which heat illnesses are possible.
The weather service recommends that people in the path of the storm move indoors and to an interior room on the lowest level away from windows. They ask that those in vehicles or mobile homes evacuate and move inside sturdy shelters.
For the latest watches and warnings, visit the National Weather Service website.
The current conditions and forecasts are available on the Post-Gazette weather page.
Benjamin Mueller: email@example.com. Liz Navratil contributed. First Published July 26, 2012 11:00 AM