Heavy Storms Possible Tonight Across Philly Region: What To Expect And When

Heavy rainfall could slam into the greater Philadelphia region on Wednesday afternoon and evening, forecasters said. Up to six inches of rain could fall in the most severely hit areas, causing widespread flash flooding, especially in urban areas.

The storm front could also bring isolated severe thunderstorms and damaging wind gusts, which could bring down trees and power lines and cause power outages.

The most severe impacts are likely to arrive from the early evening through about midnight, though there's a chance for continued thunderstorms through around 5 a.m., according to forecasters. The Weather Channel's hourly forecast for the region indicates the heaviest of the storms will roll through between 6 and 7 p.m.

In anticipation of the storms, a flood watch has been issued for all of southeastern Pennsylvania and parts of southern New Jersey, extending from 2 p.m. Wednesday to 1 a.m. Thursday.

"A high precipitable water airmass is moving over the Mid-Atlantic and will combine with a frontal system to produce highly efficient slow moving showers and thunderstorms," the National Weather Service's Mt. Holly, New Jersey branch said. "These storms will have the potential to produce 1-3 inches of rainfall per hour which, over the urban corridor, could result in flash flooding especially over impervious surfaces."

Forecasters added that if the storm ends up "back building," meaning that new storm cells push up against the movement of the storm and keep the thunderstorms in place for an extended period of time, up to six inches could fall.

Here's the full forecast for the coming week, according to the National Weather Service:

Wednesday
A chance of showers and thunderstorms. Partly sunny, with a high near 91. Southwest wind around 5 mph. Chance of precipitation is 50 percent. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Wednesday Night
Showers and thunderstorms likely before 5 a.m., then a chance of showers. Mostly cloudy, with a low around 74. West wind around 5 mph becoming calm. Chance of precipitation is 60 percent. New rainfall amounts between a half and three quarters of an inch possible.

Thursday
A chance of showers and thunderstorms, mainly between 1 p.m. and 5 p.m. Partly sunny, with a high near 88. Calm wind becoming north around 5 mph in the afternoon. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Thursday Night
A chance of showers and thunderstorms before 11 p.m., then a slight chance of showers between 11 p.m. and 2 a.m. Partly cloudy, with a low around 72. Calm wind. Chance of precipitation is 30 percent. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Friday
A slight chance of showers and thunderstorms after 2 p.m. Mostly sunny, with a high near 88. Northeast wind around 5 mph. Chance of precipitation is 20 percent.

Friday Night
Partly cloudy, with a low around 70.

Saturday
Mostly sunny, with a high near 88.

Saturday Night
Mostly clear, with a low around 70.

Sunday
Sunny, with a high near 92.

Sunday Night
Partly cloudy, with a low around 71.

Monday
Sunny, with a high near 88.

Monday Night
Partly cloudy, with a low around 67.