It may seem contradictory to get more snow during a warm winter, but for Chicago, Lake Michigan has a lot to do with it.
Lake Michigan certainly isn't warm right now, but it is milder than average for early February.
As of Thursday morning, the water temperature of Lake Michigan near Chicago was 38 degrees. That's cold, but it's nowhere close to being frozen.
The fact that Lake Michigan is not frozen is part of the reason why the snow will continue to fall from Chicago to northwest Indiana Thursday night and Friday morning.
Here's why: Warmer-than-average weather has been with us for just about the entire winter. The air hasn't been cold, so the water hasn't either. Lake-effect snow occurs when cold air moves over the (relatively-speaking) warm water of a lake. Areas downstream of the flow of air can get hit with bands of moderate to heavy snowfall.
But lake-effect snow stops once the lake is frozen. The process doesn't work when the energy from the water isn't available. It's not available when there's ice on top of the lake.
So, in an indirect way, our warmer-than-average winter is the reason why it will feel more like winter (snow!) Thursday evening and early Friday.
