Parts of western Long Island are expected to be slammed with up to four inches of snow, while eastern Suffolk and the East End will see less accumulation.
According to Tim Morrin, meteorologist at the National Weather Service office in Upton, Thursday's temperatures are at least 10 to 15 degrees below normal, hovering around 26 degrees.
That's the prelude to a blast of frosty air that's expected to hit Long Island over the coming days: Thursday night, temperatures across the board are expected to drop into the teens, with the wind chill making it feel as though temps have hit the single digits, at a brisk seven to nine degrees, Morrin said.
Friday will dawn cold, with temperatures way below normal, Morrin said, only topping around 32 degrees as a high.
Clouds will begin to move across Long Island Friday night, with temperatures dropping into the 20s.
"When folks wake up on Saturday, the sky will be gray and overcast," Morrin said. "The first flakes of snow will begin falling between 10 a.m. and noon."
Snow will be light at first, with already-cold surfaces turning slick quickly; motorists are advised to exercise caution.
Snow is expected to continue steadily through the afternoon on Saturday, with accumulations expected to reach up to four inches in western Suffolk and Nassau Counties.
Eastern Suffolk County and the East End are expected to see less snow, possibly one to two inches, due to warmer air that's slated to come in from the ocean and hit the East End first.
Snow is now expected to turn to rain overnight on Saturday across Long Island, with no precipitation forecast for the early part of next week.