I’ve watching lake-effect snow bands set up on the eastern end of Lake Erie today.
Lake-effect snow is the product of a warm lake and cold air. Because water cools more slowly than the air, this condition sets up starting in late fall and early winter.
It is essentially a very unstable set-up: the air in contact with the lake picks up a tremendous amount of heat energy and humidity below a winter-cold mass of air above.
The result, assuming temperatures support snow, is narrow and extremely efficient band of snow.