Thunderstorms Likely, Heat Advisory For 5 PA Counties Issued Friday

PENNSYLVANIA - A scorching summer day is expected to sour Friday afternoon with thunderstorms set to hit southeastern Pennsylvania, bringing potential flooding along with it, forecasters said.

Friday will kick off with “dangerously hot and humid” temperatures in the low-90s, according to the National Weather Service, a pattern that will continue through Saturday and Sunday. Heat index values on Sunday could once again top 100 degrees, forecasters said.

As of Friday morning, five Pennsylvania counties are listed under a heat advisory according to the National Weather Service, in effect through 8 p.m. on Friday. The counties are:

• Bucks
• Montgomery
• Philadelphia
• Delaware
• Chester

“For the most part, [Friday] morning will be dry, with lingering showers mostly dissipating and clouds breaking up a bit," forecasters from the National Weather Service wrote in a forecast discussion. Additional rounds of showers are slated for after 2 p.m., with isolated severe thunderstorms possible. A majority of the downpours may hit the I-95 corridor during the Friday afternoon rush hour and the weekend getaway time Friday evening, AccuWeather said.

The greatest risk on Friday remains flooding, the National Weather Service said.

“When it is raining … it could be quite heavy. Given recent expansion of moderate drought conditions, [we] held off on a flash flood watch, but day shift may re-evaluate this risk,” forecasters said.

AccuWeather notes that the flood risk is part of a pattern of torrential rain from the Ohio Valley to New England expected through Saturday that could bring localized flash flooding and travel disruptions. Around 1 to 2 inches of rain is expected, with pockets of 2 to 4 inches, but locally higher amounts are possible through Sunday, AccuWeather said.

The risk for flash flooding will be greatest along small streams, over saturated ground and along some secondary rivers, the service added. Most of the state is expected to see “drenching downpours” through Friday evening, AccuWeather said.

"Most areas from the central Appalachians and mid-Atlantic to southern New England will not have a total washout, but some random locations can be hit hard with repeating downpours that can lead to urban flooding into this weekend," AccuWeather Senior Meteorologist Joe Lundberg said.

Friday holds the highest chance of storms, with a 20 to 50 percent chance of storms in the afternoon and evening on Saturday and Sunday, the National Weather Service added.

“The weather pattern we've [seen] in the last few days continues through the weekend. Storm chances each afternoon and evening, but no day is expected to be a washout,” the National Weather Service Mount Holly station tweeted Friday morning. “Hot and humid conditions expected today & Sun; Sat will be slightly more bearable.”

Here’s the latest forecast, per the National Weather Service:

Friday: Scattered showers and thunderstorms, mainly after 2 p.m. Some of the storms could produce heavy rain. Partly sunny, with a high near 91. Light southwest wind increasing to 5 to 10 mph in the afternoon.

Friday Night: Showers and thunderstorms likely before midnight, then showers likely and possibly a thunderstorm between midnight and 2 a.m., then scattered showers and thunderstorms after 2 a.m. Some of the storms could produce heavy rain. Patchy fog after 5am. Otherwise, mostly cloudy, with a low around 72. Southwest wind around 5 mph.

Saturday: Scattered showers and thunderstorms. Some of the storms could produce gusty winds. Patchy fog before 8 a.m. Otherwise, partly sunny, with a high near 88. Southwest wind around 5 mph.

Saturday Night: A chance of showers and thunderstorms, mainly before 9 p.m. Some of the storms could produce gusty winds. Mostly cloudy, with a low around 73. South wind around 5 mph.

Sunday: A slight chance of showers and thunderstorms before 9 a.m., then a slight chance of showers between 9 a.m. and 3 p.m., then a slight chance of showers and thunderstorms after 3 p.m. Partly sunny, with a high near 90. Southwest wind 5 to 10 mph.

Sunday Night: A slight chance of showers and thunderstorms before 9 p.m. Partly cloudy, with a low around 74.