LANHAM, Md. (CBSDC) — Heavy rains have snarled traffic and brought flood warnings as Tropical Storm Andrea approaches the mid-Atlantic region.

The National Weather Service has issued a tornado watch until 8 p.m. Friday for Dorchester, Somerset, Wicomico and Worcester counties in Maryland.

The Weather Service has also issued a flash flood warning for Cecil County and parts of Prince George’s and Anne Arundel counties until 9:15 p.m. A flash flood watch is in effect for the entire Washington region until 10 p.m.

The storm is forecast to bring 2 to 4 inches of rain to immediate metro area. Isolated areas east and south of the District could receive up to 6 inches of rain. Excessive runoff from heavy rains may lead to flash flooding of low-lying areas and small streams.

The heaviest rains are expected between 10 a.m. and 8 p.m. Friday.

Hundreds of weather-related power outages already have been reported in Maryland, Virginia and the District.

Motorists are advised to drive with caution and be aware of potential ponding on the roadways.