After Tuesday’s rounds of flooding rains that doused Chester County with as much as two months’ worth of precipitation, the saturated atmosphere might be primed to wring out the sponges yet again late Wednesday afternoon.
The National Weather Service hasn’t posted flood watches, and any rains aren’t expected to rival Tuesday’s, however a walk outside reveals the obvious: The air is loaded with water, and any storms are likely to move in slow motion.
The government’s Weather Prediction Center has the entire region and all of New Jersey under an “excessive rain” risk zone. An approaching cold front, which is expected to make quite a difference by the end of the work week, would be the trigger mechanism, said Robert Deal, meteorologist at the National Weather Service Office in Mount Holly.
Although the rains cooled the air temporarily yesterday, for now the heat and humidity are back for an encore, and Philadelphia and surrounding areas are under a “heat advisory” for heat indices in the upper 90s.
And what a price for a brief cool-down. More than 7 inches of rain was measured just west of Downingtown, Chester County.
Major flooding occurred near Downingtown along the East Branch of the Brandywine Creek, which crested at 12.36 feet, one of the 15 highest on record, said Deal. Fortunately, the waters receded quickly and were back below flood stage, which is 7 feet, Wednesday morning.
Potent thunderstorms clocked South Jersey, and lightning forced guests attending the often weather-bedeviled Philadelphia Flower Show ― which is being held outdoors and in June for the first time ever ― to evacuate the FDR Park site Tuesday afternoon.
Those who held tickets were eligible to return another time, but no refunds are being offered.
Showers on Wednesday are likely to hold off until late afternoon, as all that rain on Tuesday did have one benign effect. Thunderstorms are set off by convection -- warmer air rising over cooler.
The rains cooled the lower levels of the atmosphere, said meteorologist Jim Eberwine, former marine forecaster at the weather service and now an emergency-management official in Absecon, Atlantic County. That likely pushed back the convection threat until late in the day.
Yet more rounds of showers are possible Thursday and again on Friday, when the high might not get past the low 70s.