With rain pushing sideways against the glass windows, visitors at the Carnegie Science Center yesterday watched a dark cloud race up the Ohio River, bearing down until it sideswiped the building, tore siding from one corner and shattered windows, scattering both glass and patrons who fled terrified to a ground floor.

	Bob Donaldson, Post-Gazette
	Borough workers deliver sandbags to businesses along Grant Street in Millvale yesterday. Click photo for larger image.
	More on the story Millvale forced to face flooding again and again Video: Raging waters along Girty's Run Slideshow: The day the storms kept coming Audio: Storm slams Carnegie Science Center Video: Storms force Steelers training camp to relocate Your photos: Share your storm pictures
	Pam Panchak, Post-Gazette
	Tom Flaherty, right, director of exhibits, facilities and operations for the Carnegie Science Center, and Ed Ramano, Senior Consultant for the Church Restoration Group, from Cranberry walk beneath the damaged window at the science center yesterday. Click photo for larger image.

"It was wild. People went running, screaming, people were just going in crazy in there," said Bill Oleyar, who was visiting from White Oak.

What they were seeing was the second of a three-act nature play yesterday that literally brought down the house -- or houses -- along with trees, power lines, utility poles, road signs and an assortment of other infrastructure, leaving Western Pennsylvania waterlogged, storm-weary and debris-strewn.

The first of three storms arrived between 7 and 8 a.m. and brought torrential rain, including more than 3.5 inches in McCandless and 2.5 inches in Shaler. Swollen Girty's Run flooded the town of Millvale for the second time this week. Turtle Creek overflowed and swamped the borough of Export in Westmoreland County.

The second wave hit between 2:30 and 3:30 p.m. While the science center on the North Shore was an epicenter of sorts, there were scores of damage reports throughout the region. A stretch of Fifth Avenue in Pittsburgh's Uptown district was especially hard-hit, with sections of buildings torn off and trees uprooted.

A third line of storms passed through last evening, bringing a new round of warnings from the National Weather Service and slowing cleanup and recovery efforts but causing little additional damage.

Nearly 120,000 electric customers, including about 25 percent of Allegheny County residents, lost power, and the county's emergency management chief predicted that many would be in the dark through the night.

Some 90,000 Duquesne Light customers were without power at one point yesterday. By late last night, 34,000 were still affected, and the utility was unable to say when service would be fully restored. Hardest-hit areas were Hampton, Penn Hills, Monroeville, O'Hara, Plum, Ross and Shaler. Another 19,000 Allegheny Power customers were without service last night.

Downed trees and power lines and flooded roads made mayhem of the morning and evening rush hours.

For a time yesterday afternoon, lanes on both sides of the Parkway East were blocked -- outbound by a downed tree near Grant Street, inbound by a mud slide between Bates Street and the Boulevard of the Allies.

As the second storms loomed, Allegheny County Chief Executive Dan Onorato declared a state of emergency.

As officials braced for a third line of storms around 7 p.m., the National Weather Service issued a tornado warning in Columbiana County in eastern Ohio after law enforcement officials reported a funnel cloud in Beaver Creek State Park.

A tornado warning was issued in Allegheny County during the afternoon storms, but reports of funnel cloud sightings could not be confirmed yesterday.

Twenty-four minor injuries were reported in Pittsburgh and another 10 in Allegheny County, with one victim hospitalized, officials said at a briefing last night. Some 500 homes were damaged by floodwaters, 200 of them in Millvale.

Homes were evacuated in Wilkins, Oakmont, Turtle Creek, Ross and Millvale because of flooding. The American Red Cross set up air-conditioned shelters at the Millvale Recreation Center on Lincoln Avenue; Hilltop Hall on Harper Drive, Turtle Creek; 10th Street Elementary School in Oakmont; and St. John's Lutheran Church, 715 Greensburg Ave., North Versailles.

The shelters will remain open at least through 8 a.m. today, and longer if needed.

In Westmoreland County, three construction workers were hurt, including two who fell about 25 feet, in a structural collapse at the site of the old Norwin Diner, now Jackie Joe's restaurant on Route 30, police said.

Two of the workers were on ladders tying 60- to 80-foot-wide trusses together when "the storm came in quick" about 3:15 p.m. and triggered the collapse, said North Huntingdon Officer William Sombo. "Two of them came down with it."

They and a third worker who also was injured were taken to Westmoreland Hospital after being removed from the wreckage by police, firefighters and emergency medical personnel. One had serious injuries, another had moderate injuries and a third had minor injuries, he said.

The successive lines of storms were the result of disturbances, or cold pockets of air, rippling through the jet stream along the northern edge of a high pressure system that has produced stifling heat this week across the Midwest.

Moving northwest to southeast across Western Pennsylvania, those disturbances interacted with exceptionally moist air, triggering copious rainfall, said Richard Kane, a meteorologist with the National Weather Service.

Relief is at last on the way. A cold front was expected to reach the Pittsburgh area between 3 a.m. and 6 a.m. today, bringing less oppressive heat this weekend, Mr. Kane said.

At the science center yesterday, Trevor Hays was visiting from Greenfield with a friend and said he saw "just wind going in a circle" as it bore down on the building shortly before 3.

"It looked like a funnel cloud. It turned over a couple of benches. That tree over there," he said, pointing to a battered, small tree.

A group of youngsters visiting from a day camp in the east suburbs talked of how the wind shattered glass, and blew down ceiling panels between the third and fourth floor.

"I saw the air duct explode. There was just a whole bunch of dust everywhere. The glass shattered. I heard a whole bunch of screaming, too," said Ian Pollock of Monroeville.

Center spokesman Mike Marcus said three windows were broken. The center will be closed all day today for cleanup and damage assessment.

One girl suffered a small cut. No other injuries were reported.

Mr. Marcus said that when the windows shattered, 800 to 1,000 visitors were led to the lobby and the first floors through the fire stairs in the center of the building. Many were sheltered in the theater, where the staff gave an impromptu lecture on the science of thunderstorms.

The chaotic day began shortly after daybreak when storm systems converged over Beaver County and advanced east, hitting the north and east suburbs of Pittsburgh especially hard.

Perry Highway looked more like the Perry River yesterday morning in West View, as water poured down the borough's steep main street.

Police began diverting morning rush-hour traffic away from McKnight Road after the intense storms sent water cascading across the intersection with Siebert Road, flooding parts of the road and nearby parking lots. A small car sat with water up to its windows, windshield wipers still flapping.

A lightning strike was believed to be the cause of a fire that extensively damaged a house on Malabar Drive in Plum at around 8 a.m.

In Export, workers at mid-morning quickly moved eight mail delivery trucks and personal vehicles to higher ground as creek water swamped a parking lot behind the post office at 5820 Kennedy Ave., postmaster Mary Ellen Kucenic said. Neither the vehicles nor the building was damaged.

Bus service had to be stopped in the most flooded areas of Millvale, Shaler, Etna and Aspinwall.

Bob Grove, spokesman for the Port Authority, said even the detours around flooded areas weren't passable. Affected were the 1A New Kensington, 91A Butler Street, 1D Mount Royal Boulevard and 1F Millvale.

The 67F Trafford route was delayed by a mud slide in Pitcairn, and all routes along McKnight Road were detoured and experienced at least 15 to 20 minute delays. The 61C from McKeesport through Homestead to Downtown was delayed because of flooding on Route 837 near the Rankin Bridge.

Transit service was restored to all areas except Millvale and Etna by noon.

As the cleanup continued in flooded Millvale and on major roads elsewhere, more storms struck in mid-afternoon, accompanied by a tornado warning for northern Allegheny County.

Along Fifth Avenue, in Pittsburgh's Uptown district, several buildings were damaged by high winds. Gusts blew off siding, tore down signs and caused bricks to rain down in the area between Dinwiddie and Kirkpatrick streets.

At the Hilton Pittsburgh, Downtown, a 60-foot hanging scaffolding that had been lowered to the ground was picked up by the wind and thrown into a taxicab.

The driver, George Koller of Bethel Park, who was uninjured, said at first he thought he had been hit by a car, then he realized the impact was from the direction of the sidewalk.

Just blocks away, at Sixth Avenue and William Penn Place, a light pole fell onto another cab.

Police reported a lightning strike shortly after 3:30 p.m. at a building at Fifth and Craft avenues in Oakland. Cars were reported submerged by flooding at Idlewood Road and Bell Avenue, East Carnegie.

City public works crews were still clearing downed trees and branches from roads in Schenley Park last evening.

Trees were uprooted on Spencer Lane, Middle Road and Bluestone Drive, Sapling Street and Limestone Drive in Shaler.

A tree was down yesterday afternoon across Center Road in Monroeville, headed toward Plum, backing traffic that exited from Route 48. Along Leechburg Road in Penn Hills, the parking lot at Shrodi's Place restaurant was knee-deep in water.

A stretch of Route 837 from Clairton to Lebanon School Road in West Mifflin was closed because of a large sinkhole.

In Wilkins, a portion of Brown Avenue near Washington Street collapsed due to the storm and was closed to traffic last night.