The first major winter storm of the season is hitting the Great Lakes right now. The weather radar at Intellicast shows lake-effect snows hitting both the upper and lower peninsulas of Michigan. As the air moves over the Great Lakes, it picks up moisture, which is then dumped as snow over the land downwind.
Lake effect snows produce the greatest amount of precipitation when the air is cold but the water is still relatively warm. The greater the contrast, the greater the precipitation. Over the Great Lakes, these types of storms typically occur less frequently in late winter, as either the lakes freeze over, or as the lake water temperature decreases, which reduces evaporation.
I love snow; I wish I were there.
Wikipedia article: Lake effect snow.
Grace and Peace