Timelapse footage captured in Oswego, New York, shows snow building up on Sunday, November 20, as the National Weather Service warned of heavy lake-effect snow. According to the NWS, Lake Effect Snow (LES) is very common across the Great Lakes region during the late fall and winter. "LES occurs when cold air, often originating from Canada, moves across the open waters of the Great Lakes. As the cold air passes over the unfrozen, and relatively warm waters of the Great Lakes, warmth and moisture