The National Weather Service has issued a tornado watch for Chester County until 11 p.m. Wednesday with strong storms expected elsewhere in the Philadelphia region west of the Delaware River.

“The atmosphere is primed for brief tornadoes,” the weather service office in Mount Holly said in its afternoon discussion. Areas well to the west of the city were viewed as the likeliest targets, and no other counties in the region were included in the watch.

What was left of Tropical Storm Fred passed through Western Pennsylvania during the afternoon, a track slightly west of what had been expected, but it has been having impacts on Philly’s weather.

For much of the day, most of the Philly area experienced sunshine, however that might have provided fuel for thunderstorms expected to arrive in the early evening.

The government’s Storm Prediction Center has most of the region west of the Delaware in the “slight risk” zone for severe weather with a 5% chance of tornadoes.

Meanwhile, the thunderstorm lottery is due to continue with shower chances every day through Monday.

Although Fred will be long gone, Tropical Storm Henri was about 280 miles south of Bermuda and on the verge of becoming a hurricane. It was forecastfollow a northward track well east of New Jersey.

But the National Hurricane Center warned to that could stir up “life threatening” rip currents during the weekend and come close to have some affect rainfall in the Philly region Sunday or Monday, forecasters said.

This is a developing story and will be updated.