A flood advisory for New York City has expired, but the threat of showers with scattered thunderstorms "will persist through the remainder of the afternoon and into early this evening," the National Weather Service said Wednesday.

Potentially heavy rain may result in flash flooding in the city, but the threat is expected to "diminish" by nightfall, the weather service said.

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Scattered showers and thunderstorms are also possible in Nassau and Suffolk counties, the weather service said.

A small cluster of fast-moving thunderstorms early in the afternoon prompted the National Weather Service to issue a flood advisory for the city, and the Federal Aviation Administration reported weather-related delays at LaGuardia and Kennedy airports.

As of just before 4 p.m., arrivals at LaGuardia Airport were delayed an average of 2 hours, 20 minutes, and those at Kennedy, just over two hours, according to the FAA website. Some departures at those airports, as well as at Long Island MacArthur, were affected and the FAA advised travelers to check with their airlines.. The advisory expired at 2:45 p.m., but at the airports a ground traffic management program remained in effect

With Patricia Kitchen