Early morning drivers on Long Island can expect slick conditions — a glaze of ice — even on main roads Friday, the National Weather Service said.

The service issued a winter weather advisory, in effect from 10 p.m. Thursday through 10 a.m. Friday, urging drivers to “be prepared for slippery roads and limited visibilities.”

That’s as 2 to 3 inches of snow forecast for most of the Island will last into the Friday morning commute, said Jay Engle, weather service meteorologist based in Upton. The East End could see as much as 4 inches.

In this kind of scenario — freezing temperatures and dry, powdery snow — “every flake you get counts,” he said.

On Thursday, public works departments on Long Island prepared for the arrival of snow. The Nassau County public works department pre-treated major roads, bridges and overpasses with brine to prevent black ice from forming, the county said in a news release.

Also, Town of Islip trucks brined roadways throughout the day Thursday to make Friday’s morning rush hour traffic “safer for the driving public,” town officials said in a statement. Snow equipment was ready for action, and departments involved in snow removal were on standby, officials said.

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Friday’s high temperature is forecast to be in the mid-30s, with Saturday reaching around 30 degrees, the weather service said.

Forecasters also have their eyes on a system for Saturday, with much uncertainty as to its track and impact on Long Island. As of late afternoon Thursday, the forecast was for a 50 percent chance of snow Saturday, with timing and possible amounts still in question.