The National Weather Service has issued a flash flood watch for the Philadelphia area and was alerting suburban residents to potential flooding by mid-morning.

At 10 a.m., the watch was upgraded to a flash flood warning in central Delaware County. The weather service said more than two inches of rain fell in an hour during a strong thunderstorm. The flood warning for rural Delaware County is in effect until 2 p.m.

And shortly after 9 a.m., the weather service issued a flood advisory for parts of Montgomery, Delaware and Chester counties. The advisory, which is in effect until 1:15 p.m., says that more than an inch of rain has already fallen in some areas and excessive runoff would likely lead to floodingin urban areas, streets, highways, underpasses and other low-lying spots.

The flood watch, which covers the bulk of southeastern Pennsylvania and southern New Jersey, is in effect from 8 a.m. through late tonight.

The weather service said considerable flash flooding was reported near Washington, D.C., this morning and storms were moving northeast.

Showers today are likely to be slow-moving and capable of producing one to two inches of rain per hour.

Conditions are "favorable for short term excessive deluges," a weather service forecast discussion says.

The high temperature today is expected to reach 82 degrees.

For the weekend, forecasters are calling for scattered showers and thunderstorms, with a high temperature of 86 degrees on Saturday and a high of 89 degrees Sunday.