Debby-related rains prompt flood warnings in the Philly region, with more to come

The details for what meteorologists believe will be an eventful week remain moving targets, but it was evident on Tuesday that the volatile atmosphere was super-charged with energy; brimming with moisture; and with a major assist from Debby, aiming to douse the Philly region’s rain deficits.

Quick-hitting thunderstorms began rumbling through the region Tuesday afternoon and rains became heavy during the night. A Debby-related flood watch that was in effect through Wednesday morning. And chances are that won’t be the last flood advisory of the week, forecasters are warning.

The future path of Tropical Storm Debby, which was soaking the Carolinas Tuesday, is likely to undergo changes in the next few days. It also was unclear whether it would retain its identity by the time it approaches the region during the weekend.

But that’s almost beside the point, said Robert Deal, the science and operations officer at the National Weather Service Office in Mount Holly.

“It’s a tropical air mass,” he said, “whether it’s an extra-tropical, post-tropical, or a tropical system, the event for us is quite a bit of heavy rainfall,” he said.

Downpours Tuesday night set off a region-wide flash-flood warnings, and some road flooding was reported in Bucks County, along with at least two water rescues, and in Camden and Burlington Counties. Just over 4 inches was measured in the city of Camden, nearly 4 in Willingboro, and over 3.5 in Washington Crossing, Bucks County.

Flooding suspended PATCO service between the Collingswood and Woodcrest Stations, and downed wires knocked out SEPTA Regional Rail service between Media and Wawa in Delaware County.

More showers were likely Wednesday, and the weather service hourly forecasts for Philly to have wall-to-wall rain potential for every hour until 6 p.m. Saturday.

» READ MORE: Meteorologists warned us this would be a busy season

Severe storms and isolated downpours were in play, even though Debby’s center still was hundreds of miles away on Tuesday. More heavy rains were expected later in the week as the center comes closer.

Meteorologists were certain that the entire region would get a generous drenching between now and Saturday as Debby’s northward tropical moisture plumes continue interacting with a storm-inciting front sagging southward.

The weather service said that 2 to 3 inches of rain were possible across the region Tuesday into the Wednesday alone, with substantially more later in the week.

Debby was near the South Carolina coast late Tuesday afternoon with peak winds of 40 mph, and was forecast to meander in the Southeast for the next few days.

As much as 16 inches of rain was forecast to fall along with Carolina borders, with catastrophic flooding “likely,” the National Hurricane Center said.

Debby eventually will move inland and pick up forward speed later in the week as it moves northeast, the hurricane center says, with its remnant center expected to pass near Philadelphia Saturday morning.

That predicted path has jogged noticeably westward, with the center appearing to pass west of the region. Dave Dombek, senior meteorologist with AccuWeather Inc. said. It is possible that the heaviest rains later in the week ultimately could fall to the north and west of I-95 as Debby approaches.

But that’s not close to a done deal. About the only thing certain is that the track is going to continue to undergo changes.

Meteorologists agreed Tuesday that the region was in for a stormy night. “Somebody could get really hammered,” said Dombek.

» READ MORE: Debby already has impacts on operations at the Philly airport

The weather service’s Deal said said that “training” — that’s when clusters of thunderstorms keep pounding the same areas — is possible, and that wherever that happens, it will bump up rain totals.

The agency is labeling this a “predecessor rainfall event,” and what happens between now and noon Wednesday could have a significant effect on the flood potential later in the week.

“We’ll go through the day and see how it primes the soil moisture,” he said. “Then we’ll assess what kind of impacts it will make the rest of the week.”

An isolated tornado later in the week, especially in the Delmarva peninsula or extreme South Jersey, isn’t out of the question, said Dombek.

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It’s also quite likely that in the end rainfall amounts aren’t going to be uniform, not unlike those in a late-March snowfall.

“When we look at the totals, we will have some real variations over short distances,” Dombek said.

Rain deficits have been growing. In the 60-day period that ended Monday, precipitation was about two-thirds of normal in the city and in Delaware and Montgomery Counties, and just 57% of normal in Bucks County, according to the government’s Middle Atlantic River Forecast Center. That almost certainly is going to change.

Also, Debby might restore normality to the Atlantic, where surf temperatures off Atlantic City have been running in the May-like 50s, a wetsuit situation for bathers. That’s the result of upwelling, caused by persistent winds from the south that have blown away the warm top layers of water.

» READ MORE: ‘Upwelling’ at the Jersey Shore drops the surf temperatures into the May-like 50s

“I’ve never seen the water temperatures this chilly so late in the season,” said Dombek.

As Debby approaches, it likely will generate onshore winds from the east. Those won’t be the best of conditions for beach-goers, but at least the winds would lure back the warm water.