PITTSBURGH -- A slow-moving severe thunderstorm dumped several inches of rain and egg-sized hail, quickly flooding southwestern Pennsylvania roadways Wednesday evening as Doppler radar indicated storm rotation that prompted officials to briefly issue a tornado warning.

Slideshow: Cars Flooded Throughout SW Pennsylvania
RAW Video: Flooding Turns Electric Avenue Into Raging River
Weather Watch 4: Latest Forecast, Livestream, Interactive Radar

A widespread storm system darkened the southwestern Pennsylvania sky and moved into the Pittsburgh region by 7 p.m. Earlier in the evening, NWS officials issued a tornado watch for the entire WTAE Channel 4 Action News viewing area, essentially south of Interstate 80, until 10 p.m. The NWS issued several weather advisories throughout the evening, the most severe of which blanketed the suburbs along the Parkway East in Allegheny County into south central Westmoreland County. In addition to a Doppler-indicated tornado, the storm was capable of producing hail and destructive straight-line winds. Flash flood and severe thunderstorm warnings were issued for much of the area through the evening. Check The Latest Severe Weather Advisories On ThePittsburghChannel 7:00 -- Sky Turns Dark, Thunder Rolls The National Weather Service issued a tornado warning for southeastern Allegheny County and west central Westmoreland County at about 7 p.m., which was allowed to expire in a half hour. The most severe pockets of the storm were located over Monroeville and Trafford and moved on to dump heavy amounts of rain in the Delmont and Greensburg areas of Westmoreland County. WTAE Weather Watch 4 meteorologist Erin Kienzle reported that Doppler radar indicated an area of rotation in a severe thunderstorm capable of producing a tornado. There was no actual tornado-spotting immediately reported, which NWS officials will investigate Wednesday. At 7:10 p.m., Doppler radar indicated a tornado moving near Glen Hazel moving southeast at 18 mph. At 7:23 p.m., a tornado was reported near Bessemer Junction moving southeast at 18 mph, according to the NWS. More than 1,500 lightning strikes were associated with this severe storm moving through the eastern Pittsburgh suburbs in the 7 p.m. hour. 7:30 -- Rain Floods Pittsburgh, Callers Flood WTAE Phone Lines WTAE Channel 4's Jon Greiner reported some areas of the New Castle, Lawrence County, area flooded by 7:30 p.m. Kienzle reported that several areas have reported about 3 inches of rainfall. WTAE Channel 4 Action News has learned that several cars were stuck in standing water that collected on a portion of the Parkway East in Squirrel Hill near the Beechwood Boulevard underpass. By this time, more than 4,000 lightning strikes were associated with this severe storm. "This is probably going to be our most prevalent lightning maker," Ivory said. 7:45 WTAE Weather Watch 4 meteorologist Demetrius Ivory reported that the storm system blanketed the entire parkway system in metropolitan Pittsburgh at about 7:45 p.m., saying that some areas were affected by pockets of mud and standing water. 8:00 Another severe storm cell moving in from Belmont and Harrison counties in Ohio over the panhandle of West Virginia headed toward the Washington area at about 8 p.m. More than 5,000 lightning strikes were associated with this severe storm moving through the eastern Pittsburgh suburbs in the 8 p.m. hour. Weather Watch 4 observed more than 700 lightning strikes within minutes, and thousands in Westmoreland County alone. WTAE Channel 4 Action News viewers called in to report considerable flooding in areas such as East Pittsburgh, where about 3 feet of water is standing on Electric Avenue, where some cars were seen moved by the water. The Port Authority shut down the entire 9.1-mile East Busway from Downtown Pittsburgh to Swissvale because of flooding and other weather-related damage.

Flood water moves a car on Electric Avenue in East Pittsburgh. An ominous, dark cloud lingers over Pleasant Valley. Among the first areas to significantly flood includes Squirrel Hill, particularly around the Beechwood Boulevard area. Authorities close Brinton Road after a car gets stuck in the water in Wilkinsburg. The water later rose to about the height of the passenger-side window. Weather Watch 4 shows several thousand lightning strikes produced by a severe storm moving through the Pittsburgh area. The storm drops hail from the size of peas, to golf balls, to eggs from downtown Pittsburgh, Uptown, to Greensburg.

"Drivers are trained to stop in these situations, stopping and sitting is a lot safer than trying to drive through high water," Port Authority spokesman Jim Ritchie said.

Storm Rages On All Night

WTAE Channel 4 Action News tracked the storm as it continued to move east, bringing along with it another storm cell that prompted another tornado warning in the Pittsburgh area.

The storm ignited fully engulfed fires, flooded entire neighborhoods, kept emergency crews from leaving their stations and knocked out power to thousands.

Click here to continue the story and see how the storms progressed, leaving behind damage and flooding throughout the area.