The National Weather Service now has included Chemung, Tioga (NY), and Bradford counties to the Flash Flood Watch. This will go into effect at 2PM this afternoon and continue until Friday Morning.

Moisture in the atmosphere will enhance the intensity of scattered showers and thunderstorms this afternoon, making them heavier at times. Flash flooding of creeks, small streams, and urban areas may be possible in areas of locally heavy downpours. Areas that have already received substantial rainfall will be particularly vulnerable. 

Originally the National Weather Service highlighted Tioga (PA) County in the Flash Flood Watch, which will also continue until Friday Morning as well.