Philly remains under a flood watch as storms move through the area

A highly energized atmosphere was as saturated as it gets in the Philly region — literally at rainforest levels of moisture.

And, predictably, strong storms set off flooding downpours throughout the region Tuesday afternoon and evening, with flooding issues likely to continue into Wednesday morning.

While the National Weather Service flood watch was due to expire at 2 a.m. Wednesday, showers could linger until daybreak.

The weather then should improve dramatically in time to yield the stage to the man-made fireworks on what should be a splendid July Fourth weekend. But the region may have to deal with some storm aftereffects Wednesday.

The National Oceanic and Atmospheric Administration Storm Prediction Center had Philadelphia and most of Pennsylvania and New Jersey under a severe thunderstorm watch. The weather service said the amount of energy available to ignite storms Tuesday was near or above the “extreme” level.

However, by nightfall the severe threat had backed off, at least west of the Delaware River, and flooding loomed as the bigger concern.

“There’s just an unbelievable amount of water in the air,” said Dave Dombek, senior meteorologist with AccuWeather Inc. Philly’s air Tuesday was steamier than Miami’s.

The weather service already had issued numerous flood warnings by nightfall, including one for the Frankford Creek in Northeast Philadelphia, which had risen above flood stage, as had the Perkiomen Creek in Montgomery County.

The Brandywine Creek was forecast to crest past flood stage Wednesday morning in Wilmington, Chadds Ford, and Downingtown, and the Schuylkill at Norristown could come close to sloshing over, the weather service said.

Steamy sunshine earlier in the day Tuesday had added an extra jolt of volatility to the atmosphere, said Mike Lee, a meteorologist with the weather service in Mount Holly.

But also adding juice to the flood potential were significant rains Monday night and early Tuesday.

Those storms clocked parts of the region: More than two inches of rain were measured at Brandywine Regional Airport and in Wilmington.

In an incident that may have been weather-related, a 79-year-old woman from Newark, Del., was killed late Monday night when an SUV struck a tree that had fallen upon the road in Wilmington, state police said.

Not only did those rains sponge the ground and raise water levels, but the evaporation of moisture from those soakings provided more storm fuel, Lee said.

The precipitable water levels — an estimate of the amount of rain that would fall if all the water vapor were squeezed out of the atmosphere — were more than two inches throughout the region.

That would rank in the 100th percentile for saturation in this area, Lee said, and would rival rainforest levels.

Almost on schedule, strong showers popped up around here in the afternoon, and the weather service carried reports of downed trees in Cranston Heights, Del., north of Wilmington, and a gust of 49 mph on Long Beach Island, N.J.

Flood warnings were issued all over the region.

The trigger for the would-be downpours was an approaching cold front, as opposed to the more random “air mass” lottery-ball storms that had characterized June, said Brandon Buckingham, an AccuWeather meteorologist.

For the month, rainfall totals ranged from 45% of normal in Gloucester County to 128% in Chester County, according to the weather service’s Middle Atlantic River Forecast Center.

Monday night’s rains also favored areas west of the Delaware River, but everyone was likely to get a generous share in the latest round.

The good thing about the front, said Buckingham: It was moving, and was going to take the storms with it.

After the front passes, the July Fourth weekend is looking borderline fabulous.

With highs in the 80s, both Thursday and Friday, the Fourth, are expected to be clear days.

In all of June, Philadelphia had exactly one of those.