Gusting winds as high as 50 mph starting late Tuesday and potential coastal flooding are the major issues as a weakening winter storm system makes its way to Long Island, the National Weather Service said.

The storm system that piled up snow Monday and early Tuesday across the Great Plains and parts of Illinois, Wisconsin and Michigan will have fizzled out by the time it reaches Long Island late Tuesday night, the weather station in Upton said.

But it still will deliver about three-quarters of an inch of rain over a 12-hour period with wind gusts of 45 mph to 50 mph, according to Ashley Sears, a meteorologist at the Upton station.

"The winds are the main concern right now," Sears said. "We're expecting them later Tuesday, with the rain, and overnight into Wednesday."

In addition, the weather service Tuesday afternoon issued a coastal flood advisory, in effect from 7 a.m. to 2 p.m. Wednesday for the southern bays of Suffolk, Gardiners and Peconic bays, and ocean communities.

In some areas, tides are expected to be 2 to 3 above normal, and breaking waves of 7 feet to 11 feet along Atlantic-facing coastlines "will result in moderate beach erosion," the weather service said in the advisory.

The impacts will be "flooding of the most vulnerable shore roads and/or basements due to height of storm tide or wave splashover."

The encroaching system also has generated a hazardous weather outlook for most of Suffolk and Nassau counties.

Rain is most likely to start after 9 p.m. Tuesday, and carry into Wednesday morning, Sears said.

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Chance of rain during that period is 100 percent, the service said. That chance drops to between 30 percent and 50 percent from Wednesday evening to Thursday.

The service said the worst weather for the region south of Long Island Sound should come between 6 p.m. Tuesday and 6 p.m. Wednesday.

Areas west and north, including the lower Hudson Valley, should expect "a wintry mix to develop . . . which gradually changes to all rain by midmorning on Wednesday."