July 20 – July 21
Briefing 1 – 9:30 am
Widespread thunderstorms are in the forecast for late tonight, Thursday, July 20th, and during the day Friday, July 21st, raising the potential for impacts from severe weather and flooding.
Heavy rainfall leads to flash flooding; severe thunderstorms with damaging winds and hail.
Eastern PA, NJ, DE, and northeastern MD.
A squall line of thunderstorms looks likely to affect portions of the region starting after midnight tonight into early Friday morning. After those storms weaken and move out of the area, additional thunderstorms may then develop across the entire region later in the day Friday.
Excessive rainfall rates could result in flash flooding, especially in urban and poor drainage areas. Some storms could produce severe wind gusts of 60 to 70 mph, resulting in damage to trees and power lines. Dime to quarter-sized hail is possible with the stronger cells
Confidence in occurrence:
There is high confidence that there will be thunderstorms capable of producing localized flooding across most of our region, but moderate confidence in severe weather, and low confidence in storm coverage & specific timing in any one location. See the attached graphic for the current risk of excessive rainfall and severe weather. The risk of severe weather is 'marginal' (1 out of 5), while the risk of flooding is 'slight' (2 out of 5).