The watch has been issued for Berks, Chester, Lancaster, Lehigh and Northampton counties until 11:00 p.m. Friday.
That means conditions are favorable here for possible tornado development.
TONIGHT: Steady rain arrives in the early evening hours along with a gusty, drenching thunderstorm in spots. Lingering lighter rain continues overnight until close to dawn on Saturday. Some street flooding is possible in areas that receive the heavier rain cells. The low: 51.
SATURDAY: The rain ends early, probably before daybreak. Sunshine returns, but it will be windy and noticeably cooler. The high: 62.
SUNDAY: It looks like a mostly sunny, cool day with an afternoon high of only 58.
MONDAY: Sunshine gives way to increasing clouds with a high of 59 There could be a little rain arriving at night.
TUESDAY: It's mainly cloudy and breezy with some rain at times. The high: 61.
WEDNESDAY: Clouds will mix with some sun. Some lingering showers are possible. The high is 64.
THURSDAY: Sunshine returns, but it's still a bit cool. The high: 63.
FRIDAY: It's partly sunny and a bit milder with a high of 66.
