Chicago Weather: Bitter Cold Friday Morning, More Snow Friday Night; Record Cold Valentine's Day?

CHICAGO (CBS) -- Persistent lake effect snow late Thursday prompted a Winter Weather Advisory that will go into the overnight hours for Lake and northern Cook counties.

As snow showers continue, the National Weather Service said the advisory will be in effect until 4 a.m. A broader advisory for the rest of Cook County and DuPage County has been dropped.

Meanwhile, a system of snow from the west is crossing northern Illinois. This all tapers off by daybreak.

On Friday morning, the wind chills drop to 15 below. It will be dry and mostly cloudy during the day with a high of 16.

Another round of steady snow Friday night through Saturday evening could bring another 2 to 5 inches this weekend.

A reinforcing shot of Polar air moves in for Valentine's Day, when temperatures will fall below zero overnight, and reach highs around only 5.