WeatherWhys for December 10,2013 from accuweather.com

Lake-effect snowstorms run at full throttle from the second half of November through December. That's because the water in the Great Lakes is very warm compared to the arctic air that might cross them. The temperature difference is key to lake-effect snow events. However, as the lakes cool during the latter part of winter, the intensity and frequency of lake-effect snow events diminish.