Rain sets two records in Philly Saturday as a flood warning remains in effect
Up to 4 inches of rain are in the forecast in and around Philly as a storm draws in moisture from the warm Atlantic.
A flood warning is in effect until 3:15 p.m. for most of the region Saturday as soaking downpours on what has turned out to be the rainiest March day in Philly in 150 years of recordkeeping continue.
As of 1:30 p.m., 2.86 inches of rain had been measured at Philadelphia International Airport, said Mike Lee, a meteorologist at the National Weather Service office in Mount Holly, the most ever on a March day. It also was more than double the daily record for a March 23.
A potent storm drenching the I-95 corridor is generating widespread heavy rains. They are due to continue for the next few hours with final rain totals of 3-plus inches likely.
The flood watch is in place until 8 a.m. Sunday. Some minor stream and road flooding has occurred, and power outages are “possible,” the weather service says, with winds forecast to gust to 50 mph later Saturday and Saturday night.
The storm was forecast to follow a track right along the coast, putting the I-95 corridor in the bull’s-eye of the heaviest rain, said Eric Hoeflich, a meteorologist with the weather service’s Mount Holly office.
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The record for precipitation for any March day in Philadelphia had been 2.79 inches, set in 1912. The record for March 23 is 1.36 inches, set in 2005.
The warm Atlantic, not to mention El Niño
The storm, tracking from the South, will be feeding off two generous moisture supplies, said Dave Dombek, senior meteorologist with AccuWeather Inc.
“It’s tapping into some pretty moist air that’s across the Southeast,” he said. As is typical during El Niño events, when the water temperatures over vast expanses of the tropical Pacific are well above normal and affect upper-air patterns, storm tracks across the southern United States become active.
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Rainfall in the Southeast was well above average during the winter and has left a moist legacy in the air, said Dombek. The weather service said the storm will tap into “deep tropical moisture.”
Plus, with its onshore winds, on Saturday the storm will be importing moisture from the Atlantic, where sea-surface temperatures also are substantially above normal. “There’s some really juicy air, and almost borderline tropical air offshore,” said Dombek.
The potential impacts
It’s possible that some streams could slosh over, and urban street flooding is very likely, the weather service says.
Scattered power outages are in play as the ground becomes saturated.
Fortunately, most of the trees aren’t yet weighted down with leaves, and that lessens the potential for tree damage, as winds can sail through bare branches.
Also, no measurable rain had fallen in two weeks, and Dombek noted it has been quite windy, and that has contributed to drying out the soils.
The rain is expected back off by late in the day.
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The sun is due to reappear Sunday, but for the 12,000 people expected to participate in Philly’s Love Run, it will be a chilly half marathon or 7K, with temperatures in the low to mid-30s, winds from the north at 20 mph, and wind chills in the upper teens. At least it should be a dry run.