Photo of barge that struck the Vine Street interchange over the Schuylkill River due to heavy rain and flooding last week.
© Alejandro A. Alveraz
Photo of barge that struck the Vine Street interchange over the Schuylkill River due to heavy rain and flooding last week.
Once again downpours have developed across the Philadelphia region Wednesday, and the National Weather Service has issued fresh rounds of flood advisories and storm warnings.

Flood warnings covered areas from Chester County, through parts of Philadelphia, into South Jersey at mid-afternoon where up to 2 inches of rain already had fallen.

Three separate severe-thunderstorm warnings were in effect at mid-afternoon on both sides of the river, and a flash-flood watch for the entire region remains until 11 p.m., with rainfall rates of 1 and 2 inches an hour expected along the I-95 corridor, the weather service said.

And some of the region's streams are about up to here with all this rain and are primed for another slosh-over, the weather service says. Rainfall last week in some areas incredibly was close to 1,000% of normal, according to the Middle Atlantic River Forecast Center.

In its noon update the government's Weather Prediction center had the entire region under a "moderate risk" for "excessive rainfall," with isolated rates of 2 and 3 inches an hour possible.

What's more, the atmosphere, possibly suffering from exhaustion, doesn't appear to be in a big hurry to move things along, so any showers that form could become stuck for a while, moving on the order of 5 mph, like a car with a flat tire, the weather service says.

Meanwhile, the agency on Tuesday added one more to last week's tornado count, confirming a twister that touched down in Milford, Sussex County, and crossed into Kent County. It was the third Delaware tornado of the week in a state that averages a grand total of one annually.

In all, the Mount Holly office confirmed eight Isaias-related tornadoes in its service territory, including one in Maryland. On Monday it added one that cut a nearly four-mile path in New Castle County on Friday, with a peak wind speed of 105 mph.

The government's Storm Prediction Center in Norman, Okla., has the region under a "slight risk" of severe thunderstorms on Wednesday, but the weather service says the biggest threat will be the potential for heavy rain.

Why all the rain? In summer, the upper-air currents that steer weather systems can become quite lazy, so whatever happens tends to keep happening.

"You get stuck in a pattern," said Valerie Meola, meteorologist at the Mount Holly office.

If you're stuck in this one, it's good to keep a poncho handy.

Last week's countywide average rain totals look almost hallucinatory. Over eight inches fell upon Delaware County in the seven-day period that ended on Sunday. That was 947% of normal, according to the River Forecast Center in State College, Pa.

Chester County, where over 10 inches was measured in West Chester from Isaias and Friday's outbreak, came in at 850% of normal.

Based on the flash-flood guidance, the weather service says, it wouldn't take much to coax some streams out of their banks on Wednesday.

(More here)