The National Weather Service is predicting a pre-Thanksgiving nor'easter to hit Long Island that has the potential to snarl travel plans on the busiest day of the year.

The storm is set to begin sometime Tuesday and extend into Wednesday, said Joe Pollina, meteorologist with the service's Upton bureau.

But just how strong the storm will be on Long Island remained unclear Sunday. Pollina said that while the coastal storm is forecast to hit the area, where and how is "still in question."

"We just know this storm looks like it's going to impact the area," he said. "The amount of rain and how high the winds might be is questionable."

The best advice, especially for those traveling for Thanksgiving, is to "stay tuned to the forecast," Pollina said. "We fine-tune it as we get closer to the event."

Once the nor'easter comes and goes, Thanksgiving itself will be comparatively mild -- although the holiday's high temperatures will still be quite below normal.

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Thursday's high will be in the middle to upper 30s, with mostly sunny skies and no chance of precipitation.

The normal average high for this time of year is around 50, with lows in the middle 30s, Pollina said.

The chill is courtesy of a surge of colder air brought to the area by the storm, he said.

An earlier arctic air mass brought teeth-chattering temperatures to the area Sunday, with similarly chilly weather expected for Monday.

Highs Monday were forecast to be in the low to middle 30s, with lows in the upper 20s to low 30s.