Lake Effect Snow Band

Provided and copyright by: Steve Irvine
Summary authors & editors: Steve Irvine, Jim Foster, Stu Witmer

The Great Lakes in North America are sufficiently large that they have a significant influence on weather at both local and regional scales. "Lake effect" snowstorms develop when large temperature differences exist between that of the warmer lake water and the cold winds blowing across it. Blizzard conditions frequently occur in the lee of large bodies of fresh or salt water following the passage of a cold front. Bands of moisture-laden clouds may dump snow as far as 60 miles (about 100 km) inland. In some extreme lake effect events, upwards of three feet (one meter) of snow will fall during a 24-hour period. The snow producing cloud band pictured above formed over Georgian Bay, a northeast arm of Lake Huron, on February 11, 2008.

Because water has a high thermal inertia, it heats up much slower in summer than does adjacent land surfaces and cools down in fall more slowly than land. Air moving across large water bodies, such as the Great Lakes or Bay of Fundy (see tomorrow's EPOD), can result in different weather related phenomena depending upon the differences between the air and water temperature.