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 lake effect snow storm. 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.