Long Island Forecast: Timeline For Severe Weather This Weekend

The weekend will start out nice enough with highs in the mid-70s under mostly sunny skies through Saturday afternoon on Long Island. But it will abruptly turn not so nice as a storm system moving up the East Coast Saturday night could bring thunderstorms capable of producing isolated damaging wind gusts or a brief tornado to the island, the National Weather Service says in a hazardous weather outlook issued for the region.

Rain will likely be falling by sunset Saturday, but the greatest chance of severe storms will be overnight into early Sunday. A window from around midnight until 6 a.m. Sunday is when the island will likely get the worst of it.

Here's what Joe Cioffi, a meteorologist for WPIX-TV and FiOS1 News, wrote on his website Friday:

Spiral bands of downpours will be sweeping around low pressure in Eastern Pennsylvania. In those bands are likely to be some thunderstorms and it is from this that the Storm Prediction Center has a marginal risk for severe weather. We have seen cases like this produce tornadoes and waterspouts so I would not at all be surprised if this happens.

The heaviest rain will shift mainly to the East End during Sunday morning, but after a short break, chances for showers and isolated thunderstorms may increase in the afternoon as tropical moisture continues to stream northward, the NWS says.

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The wet weather may stick around the entire workweek.

"A nearly stationary frontal system in the wake of this low could then produce showers and thunderstorms capable of causing flash flooding through much of the week," the NWS says.

The full forecast:

Saturday- Mostly sunny, with a high near 75. East wind 7 to 15 mph.

Saturday Night- Showers, with thunderstorms also possible after 1am. Some of the storms could produce heavy rain. Steady temperature around 71. Breezy, with an east wind 17 to 25 mph, with gusts as high as 41 mph. Chance of precipitation is 90%. New rainfall amounts between three quarters and one inch possible.

Sunday- Showers likely and possibly a thunderstorm before 7am, then a chance of showers. Mostly cloudy, with a high near 81. South wind 14 to 17 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Sunday Night- A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 3am. Cloudy, with a low around 74. South wind 9 to 11 mph. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.

Monday- Showers likely, mainly before 1pm. Cloudy, with a high near 83. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Monday Night- A 50 percent chance of showers. Mostly cloudy, with a low around 74.

Tuesday- A 40 percent chance of showers. Mostly cloudy, with a high near 84.

Tuesday Night- A 30 percent chance of showers. Mostly cloudy, with a low around 74.

Wednesday- A 40 percent chance of showers. Mostly cloudy, with a high near 83.

Wednesday Night- A 50 percent chance of showers. Cloudy, with a low around 73.

Photo of a waterspout off Smith Point Beach last year by Mason Coraci