For lake-effect snow bands to form, a few key ingredients are needed, including warm waters, moisture, a forcing mechanism, such as a cold front, and fetch.
Imagine having a lake during the early winter season. With bodies of water cooling slower than land, you get lakes that can be at least 20 degrees warmer than land, and much warmer compared to the air about 4,000 feet above the surface. The difference in temperature between the water and air can be as much as 45 degrees Fahrenheit, or 25 degrees Celsius.
With the difference in temperatures and enough moisture from the lake, condensation forms. A forcing mechanism is then needed to drive this energy onto land. A cold front is a good example. The rushing cold air mixes with the warm air and flows from the lake onto land.
Moisture and fetch:
In terms of lake-effect snow formation, the more moisture, the better. Fetch is known as the distance wind travels over the warm lake. The longer the fetch, the more moisture, which can lead to heavier lake effect snow. Think of Lake Erie as an example. Fetch is longer when winds travel northeastward. When this happens, cities like Buffalo, NY can get hit the hardest.