Flash-flood watch for Nassau lifted

There's still a 40 percent to 50 percent There's still a 40 percent to 50 percent chance of precipitation Friday evening into early night in the form of scattered showers and thunderstorms -- some possibly heavy in localized areas, said David Stark, meteorologist with the National Weather Service based in Upton. (June 28, 2013) Photo Credit: Weather Underground

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A flash flood watch for Nassau County has been lifted, indicating that conditions are no longer conducive for widespread, heavy rain Friday afternoon and evening -- but that's not to say you should leave behind your umbrella.

There's still a 40 percent to 50 percent chance of precipitation Friday evening into early night in the form of scattered showers and thunderstorms -- some possibly heavy in localized areas, said David Stark, meteorologist with the National Weather Service based in Upton.

As with any localized, heavy rainfall, there's also the chance of localized flooding, he said.

The weather service also announced a "high rip current risk" along ocean beaches through 9 p.m. Friday and again from Saturday morning through evening.

This as a somewhat unpredictable weather pattern calling for an elevated risk of severe thunderstorms continues through the weekend and likely into next week, the National Weather Service said Friday.

With what the weather service calls "a broad area of low pressure" over the Northeast, Friday's traffic at area airports has been affected. As of late afternoon Friday, arrivals into LaGuardia Airport are averaging weather-related delays of just over an hour and a half, with flights coming into Kennedy Airport delayed, on average, three hours and 15 minutes, according to the website of the Federal Aviation Administration.

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Some departures from those airports, and from Long Island MacArthur in Ronkonkoma, are also delayed, and the FAA advises travelers to check with their airlines.

While a deluge of overnight rain missed most of Long Island, pushing farther inland and north than originally forecast, hot, humid weather persists, creating a threat of wicked thunderstorms, said Tim Morrin, a meteorologist with the Upton-based service.

"Depending on where those storms develop, almost any region can get a quick burst of heavy rain at any point," Morrin said.

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So, through Thursday, the Fourth of July, it's partly cloudy skies, muggy days and the persistent threat of a severe storm, mostly in the afternoon hours. The daily chance of precipitation for each day, including the holiday, ranges from 30 to 60 percent.

The elevated risk for severe thunderstorms means any storm, at any time, could turn severe, Morrin said.

"We're in a real moist pattern," he said, "where the heating of the day percolates the atmosphere. When you get this kind of mechanism that moves moist air upward, you can have a deluge in any one location."

The heavy overnight rain -- Thursday into Friday -- forecasters had expected ended up farther north, striking Hudson Valley, northern New Jersey and parts of upstate New York, Morrin said.

No part of Long Island, he said, got more than a quarter-inch of overnight rain.

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Because of the daytime heating and the rush of air from the south and parts of the southern Atlantic, rain patterns can change quickly, Morrin said.

"It's just so chaotic," he said. "Sometimes you get a really good handle on it; other times it's just wait and see."

With Gary Dymski

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