A potent, drought-interrupting tropical rainstorm pounded the region Thursday with blinding downpours and gale-force winds. But the worst may come well after the rain stops.

The heavy, fitful rains, exported by the vestiges of the short-lived Tropical Storm Nicole, have swollen headwaters, rivers, and streams throughout the region. Thus the National Weather Service warned that at least moderate flooding is possible as some of those waterways crest Friday afternoon and Saturday morning.

Flooding and wind damage caused sporadic traffic woes Thursday night.

SEPTA reported that the Paoli-Thorndale outbound line was halted - but later restored - due to a fallen tree on the track, and the Chestnut Hill East line was suspended because of downed power lines.

In Delaware County, police said the intersection of Route 291 and Stewart Avenue in Ridley Township was completely flooded and traffic in all directions was being turned back.

In Chester and Montgomery Counties, there were reports of limbs down and sporadic power outages, but police said there were no reports of injuries.

Philadelphia International Airport reported delays of between one and two hours because of strong winds.

Philadelphia police said that there were incidents of downed trees, but that the roads were clear as of 10:20 p.m.

Looking to Friday and Saturday, Pennsylvania Gov. Rendell put the state National Guard on alert for flooding trauma; SEPTA advised commuters to prepare for delays on even more flood-sensitive transit lines, such as West Trenton and Norristown; and Philadelphia police were prepared to close off flood-prone roads, including Kelly Drive and Columbus Boulevard.

City officials set up shelters at Roxborough High (6498 Ridge Avenue) and Bartram High School (2401 South 67th Street).

If Philadelphia gets four to six inches of rain, the Schuylkill could crest at 14 feet, which is three feet above flood stage.

"During the height of storm, stay safe. Drive only if necessary. If you must drive, avoid low-lying areas and standing water," Mayor Nutter said in a statement. "Please take extra precaution to secure lawn furniture, trash receptacles, and other loose objects outside, because high winds are anticipated. Downed trees and power lines are also expected."

A high-surf advisory was issued for the Jersey Shore, with waves approaching eight feet. But predictions Thursday were that neither the Rancocas nor Assunpink Creeks would crest above flood stage.

At least one death was blamed on the storm Thursday, as were significant airport delays in the morning and countless traffic accidents.

In all, the storm has been implicated in five deaths in the Mid-Atlantic region, and Joe Bastardi, a meteorologist with Accu-Weather Inc., said it could end up causing $100 million in damages.

By the time the rain ends Friday, meteorologists say storm totals could reach prodigious levels, perhaps 6 inches or more - or about two months' worth over a region where residents have been asked to conserve water because of drought conditions.

Moderate flooding was possible Friday afternoon along the Schuylkill and the Neshaminy Creek, and along the Delaware River on Saturday morning, the National Weather Service said.

"It takes time for all the rain to work its way into the system," said James Hayes, a weather service meteorologist.

Chester County, where fallen trees closed roads and prompted officials to send some students home early, declared a state of emergency, as did Lancaster County. Chester County's Unionville-Chadds Ford School District canceled Friday classes.

As crests approach Friday and Saturday on waterways, expect rising anxieties.

The Delaware River at Trenton is expected to crest at 21 feet Saturday morning, or about a foot over flood stage. The Neshaminy and Brandywine Creeks are forecast to rise well above flood stage Friday afternoon.

The rains have been wrung out from the amorphous vestiges of erstwhile Tropical Storm Nicole. Once its peak winds dropped below the naming threshold, 39 m.p.h., it was stripped of its title, but not its juice.

During the day the heaviest rains fell just to the north and west of the Philadelphia region. More than four inches was measured in Allentown. But plenty fell around here.

It was during a downpour that a motorist was killed Thursday morning when his Dodge Durango spun out of control and slammed into a tree on the Pennsylvania Turnpike in Chester County, police said.

A four-car pileup on Kelly Drive in Philadelphia was attributed to weather conditions.

Flight delays of up to two hours were reported at the airport during the morning.

Nicole's leftovers could have one beneficial effect. The rain totals from this one storm could end up exceeding the total for the previous 60 days.