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Ellicottville got buried on Monday; by nightfall the western New York town was under two and a half feet of snow. Glenwood, just twenty miles away, had two inches. The culprit was a . Unlike typical winter storms, which can sprawl across states, lake effect snow storms are bands just ten to twenty miles wide. They form as cold air blows across warm water. Inside a band, a foot of snow can fall in a matter of hours, accompanied by thunder and lightning, while just outside skies might be blue.

Lake effect snow storms are a matter of physics. Air cools quickly, the reason why Arctic blasts like the one presently chilling the eastern United States are possible after such recent warmth. Water takes longer to cool, which is why, despite the current cold, no body of water much larger than a puddle will begin freezing anytime soon. The Great Lakes typically don’t freeze over until January or February, making November and December prime months for lake effect snow squalls. Cold fronts sweeping south out of Canada bring winds that can blow in the same direction for days. Cold air over warm water generates evaporation. Cloud bands form and begin to dump snow, but intensity diminishes with distance. A town fifty miles from the lakeshore might just see flurries.

Lake effect snow storms are bands just ten to twenty miles wide inside of which a foot of snow can fall in a matter of hours, accompanied by thunder and lightning.  (Courtesy of NOAA).

Lakes must be sufficiently large to form lake effect snow bands; the Great Lakes are all over one-hundred miles long and some are equally as wide. Areas of Turkey receive lake effect snows, provided by the Black Sea, and parts of northern Japan experience them too, but Lake Ontario, in upstate New York, generates some of the heaviest snows of all. The dumped 102 inches of snow on Oswego, New York over five days in January, 1966.