Lightning Tuesday on Long Island.

Lightning Tuesday on Long Island. Credit: Newsday / Cecilia Dowd

Suffolk and southern Nassau are under a tropical storm watch, with Elsa on the way, the National Weather Service says.

Although the tropical storm will weaken on its way up, forecasters now say it may regain strength as it approaches Long Island late Thursday night and rolls through Friday.

"Tropical Storm Elsa will move over Georgia tonight, and through the Carolinas on Thursday, while weakening to a tropical depression. The storm will then reintensify to tropical storm strength as it passes near or over the Mid Atlantic coast late Thursday night, and near or over Long Island and southeast New England on Friday," the weather service said.

In a briefing issued Wednesday evening, the weather service said there is a "2 in 10" chance that the storm will bring sustained winds of 39 mph of more, or tropical storm force, when it arrives on Long Island.

The weather service also said that during the same time, there will be a "brief period of south to southeast winds of 35 to 40 mph with gusts to 55 mph" possible for portions of Long Island.

Elsa is also forecast to bring one to three inches of rain from about 2 a.m. Friday to noon, along with minor coastal flooding, high surf and dangerous rip currents.

"The main threats from Elsa are heavy rain capable of producing flash flooding, tropical storm force winds especially along the south shore of Long Island and across southeast Connecticut, and associated marine and coastal hazards, including very rough seas and dangerous rip currents," the weather service said.

The new watch means tropical storm-force winds of 39-mph or more are "possible somewhere" within the area in the next 48 hours, the weather service said.

The weather service added that Elsa will also bring conditions "somewhat favorable" for tornadoes.

For Wednesday, the weather service has also issued a severe thunderstorm watch for Long Island and the entire tristate area until 11 p.m.

The heat advisory that began on Tuesday continues through 8 p.m. Wednesday as the heat index pumps up the feel of the air to about 101 degrees even though the temperature stayed below 90 degrees in many places on Long Island.

There is also an air quality health advisory for Long Island due to high levels of ozone until 11 p.m.

The weather service, which issued a hazardous weather outlook, also warned Wednesday of a high risk of rip currents — which can speed out to sea faster than an Olympic swimmer at 5.5 mph — at New York's ocean beaches.

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