UPDATE The National Weather Service in Upton, N.Y. has issued a severe thunderstorm warning for Westport and parts of the tri-state area until 7:30 p.m.
An advisory at 6:55 p.m. upgraded a severe thunderstorm watch issued an hour earlier to a warning.
It said thunderstorms in advance of an approaching cold front will move across the area this evening. Some thunderstorms could produce damaging winds and large hail with perhaps an isolated tornado.
Some of the thunderstorms would also produce very heavy rain with localized flash flooding as well as frequent lightning, it said.