A flash flood watch has been issued for Grafton and Coos counties until 4 a.m. Sunday.Thunderstorms and heavy downpours will move into mainly northern and western New Hampshire on Saturday evening and overnight. Some of the storms could contain torrential rainfall, particularly over areas already hit hard by flash flooding earlier this summer. If you are camping or live near a stream or river, have a plan in place to evacuate if necessary, or if you encounter a flooded roadway, do not drive through the water. Sunday will be mostly cloudy again with highs in the 80s and high humidity. Another round of scattered downpours and storms will be likely.