Lake Effect Snow

Earlier this week, Erie residents woke up to 24 inches of new snow. Last year, the area received 58.1 inches of snow in January alone. During the fall and winter, many areas of the eastern United States and Canada experience tremendous amounts of snowfall. This snow, known as "lake-effect snow," is generated from the temperature contrast between the cold arctic air moving over the relatively warm waters of the Great Lakes (or other large body of water). Unlike most winter storms, lake effect snows do not build their foundation upon strong areas of low pressure. Instead, they are fueled by the same dry arctic air that is responsible for clearing skies over land in other parts of the country. Specifically, cold arctic air passing over the Great Lakes picks up moisture and deposits it as snow inland from the downwind shore. So while other parts of the northeastern United States are clearing up after a recent cold frontal passage, communities near the Great Lakes wait for the lake effect snow machine to fire up.

Lake-effect snow cloud bands are remarkably persistent and have been known to cause continuous snowfall for as long as 48 hours over a sharply defined region—an amount that often exceeds that of a typical winter storm (i.e., one associated with a low pressure). Lake effect snows yielding as much as 76 inches of light-density snow in 24 hours and fall rates as high as 6 inches per hour have been reported. Furthermore, because winds accompanying arctic air masses generally originate from a southwest to northwest direction, lake effect snow typically falls on the east or southeast sides of the lakes. In general, lake effect snowfall contributes between 30 and 60 percent of the annual winter snowfall on the eastern and southern shores of the Great Lakes.

Today's wintry photo was taken by WPC Member and Volunteer Mary Shaw.

Reference: National Oceanic & Atmospheric Administration (NOAA)

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