Heavy snowfall downwind of large bodies of open water, such as the Great Lakes in North America. When a cold airstream of continental polar air (cP) crosses relatively warm water (as in the autumn and early winter) it becomes unstable, leading to mesoscale bands of cloud over the water and shoreline. Although the clouds are relatively shallow (extending to heights of perhaps 4 km), they produce significant precipitation on the farther shore. This effect is largely responsible for the extremely heavy snowstorms experienced by Buffalo, New York, for example.
Subjects: Meteorology and Climatology.