The National Weather Service issued the watch to Berks, Bucks, Lehigh, Northampton, Hunterdon and Warren counties -- in effect until 10 p.m.
The watch implies that a tornado is possible and communities should be prepared. A tornado warning, however, means that a twister is moving in on the area.
Wind gusts of up to 75 mph are also possible, as is flooding -- with up to 6 inches of rain expected across the area.
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