Lake-Effect Snow: What Causes Local Snowbelts Over Water?

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Lake-effect snow is common in regions near lakes, such as the Great Lakes in Michigan. Image courtesy of the NOAA.

Lake-effect snow is common in regions near lakes, such as the Great Lakes in Michigan. Image courtesy of the NOAA.

Lake-effect snow is common in the lee of the United States’ Great Lakes. Cities affected include Chicago, Cleveland, and Buffalo; depths are often measured in feet. What causes these local snowbelts where over 100 inches of snow per year are commonly recorded?

Cold air passing over warm water is a lethal meteorological combination. The cold air literally acts as a shovel, picking up moisture from the water, turning it into snow, and depositing it on nearby land areas. In the winter, this combination often occurs on the south and east shores of the Great Lakes, as arctic air invades from the northwest.

The Physics of Lake-Effect Snow

Precipitation is a simple process.

  • Rising air cools.
  • Cool air cannot hold as much moisture as warm air.
  • If there is enough moisture, some of it condenses and falls as snow or rain.

The lake effect does two things: It provides moisture, and warms the lower layer of air. Warm air wants to rise, and the precipitation process starts. When the air is at least twenty degrees colder than the water, it warms rapidly and picks up a lot of moisture. As soon as the air mass moves onto land, it cools again and the precipitation falls as snow.

When Does Lake Effect Snow Occur?

The Great Lakes area generally experiences the greatest lake-effect snows in November through January. As the lake water cools, the temperature contrast with the air is less pronounced, diminishing the effect. And when the lakes partially or totally freeze, the effect can shut down completely.

Who Gets the Most Lake-Effect Snow?

The wind can blow from any direction in the winter, so the Great Lakes region is, in general, a snowy place. But the most common direction of wind in the winter is from the north or west. In addition, if wind carries the moisture into elevated regions, the snow process is exacerbated.

Syracuse, New York, close to the shore of Lake Ontario, is the snowiest big city (population 100,000 or more) in the U.S. with an average snowfall of 117 inches. Buffalo and Rochester, N.Y., in the same general snowbelt, receive over 90 inches. Hancock, MI, (population around 4600) on the southeast shore of Lake Superior, the largest of the Great Lakes, averages over 210 inches of snow per year. Boonville, N.Y., at 1150 feet elevation in the foothills of the Adirondack Mountains, combines the best of both worlds (if you like snow). About 50 miles southeast of lake Ontario, Booneville receives 193 inches of lake-effect and upslope snow in an average year, and once measured 35 inches in a single day, including an astounding seventeen inches in just two hours.

Other Places That Have Lake-Effect Snow

Lake Baikal in Russia has a modest lake-effect snow, and the Great Salt lake in Utah is sometimes affected. Even smaller lakes such as New York’s Finger Lakes can have occasional squalls from lake-effect snow.

Snow Over Water

Any place where a cold wind blows over warm water is likely to have lake-, bay-, or ocean-effect snow at some time. The largest yearly snowfalls occur in the Japanese mountains on the Island of Honshu where upwards of 1200 inches (100 feet!) fall annually. This is truly a snow-lovers mecca, as cold Siberian winds blow across hundreds of miles of the Sea of Japan, then are lifted by the Japanese Alps. So if you live in Syracuse, don’t feel too bad. It could be worse — a lot worse.

Sources:

America’s Snowiest Places? USNEWS. Accessed 1/2/14

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