Lake effect snow
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Image:LakeEffect-Superior-Michigan-EO.jpg Image:LakeEffectSnowBuffalo101206.gif
Lake effect snow, which can be a type of snowsquall, is produced in the winter when cold winds move across long expanses of warmer lake water, picking up water vapor which freezes and is deposited on the lee shores. This effect is enhanced when the moving air mass is uplifted by the orographic effect of higher elevations on the downwind shores. This uplifting can produce narrow, but very intense bands of precipitation, which deposit at a rate of many inches of snow per hour. The areas affected by lake effect snow are called snowbelts.
If the air temperature is not low enough to keep the precipitation frozen, it falls as lake effect rain. In order for lake effect rain or snow to form the temperature difference between the water temperature between the surface and 850 mb should be at least 13 °C. Lake effect of extremely cold air over still warm water in early winter can produce thundersnow, snow showers accompanied by lightning and thunder.
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[edit] Cause
Even when precipitation is not produced, whenever cold air passes over warmer water it produces cloud cover. Fast moving cold fronts, known as Alberta clippers often cross the Great Lakes. After the passage of a cold front, winds tend to switch to northwest, and a frequent pattern is for a long lasting low to form over the Canadian Maritimes which may pull cold northwestern air across the Great Lakes for a week or more. Since the prevailing winter winds tend to be colder than the water for much of the winter, the southeastern shores of the lakes are almost constantly overcast, leading to the use of the term The Great Gray Funk as a synonym for winter.[citation needed] These areas allegedly contain populations that suffer from high rates of seasonal affective disorder, a type of psychological depression thought to be caused by lack of light.[citation needed]
[edit] Phenomenon in northeast United States
Cold winds in the winter typically prevail from the northwest in the Great Lakes region, producing the most dramatic lake effect snow falls on the east to south shores of the Great Lakes. This lake effect produces a significant difference between the snow fall on the eastern and western shores of the Great Lakes.
Lake effect snows on the Tug Hill Plateau (east of Lake Ontario) frequently set the daily records for snowfall in the United States.[citation needed] Syracuse, New York is directly south of the Tug Hill Plateau and receives significant lake effect snow from Lake Ontario (although much less than the Tug Hill Plateau by as much as 100 inches). In fact, Syracuse receives so much snowfall it is often considered the "snowiest" large city in America.[citation needed] Syracuse has frequently won the "Golden Snowball" award, a NOAA regional contest for greatest annual snowfall among Upstate New York snowbelt cities. Lake effect snow from the Finger Lakes occurs here as well, until those lakes freeze over. The Appalachian Mountains and Atlantic Ocean largely shield New York City and Philadelphia from picking up any lake effect snow; snow there tends to come from storm systems mixing with cold weather.
Lake Erie produces a similar effect for a zone stretching from the eastern suburbs of Cleveland to Erie to Buffalo. Lake Erie has the distinction of being the only great lake to completely freeze during the winter as a result of being very shallow. Once frozen, the resulting ice cover temporarily alleviates lake effect snow from originating there.
Another snow belt is in the Upper Peninsula (UP) of Michigan, near the cities of Houghton, Marquette, and Munising. These areas frequently average over 200 inches, and may receive close to 300 inches of snow a year (for comparison, on the western shore, Duluth, Minnesota receives only 77 inches). Lake Superior and Lake Huron rarely freeze due to their size and depth; lake effect snow can fall continually in the UP and the Ontario, Canada snowbelts during the winter months. Western Michigan and north-central Indiana can get heavy lake-effect snows as winds pass over Lake Michigan and deposit snows over Traverse City, Grand Rapids, Kalamazoo, and South Bend, but these snows abate significantly before Lansing or Fort Wayne, Indiana.
Cities such as Toronto, Hamilton, Detroit, Milwaukee, and Chicago frequently miss out on lake effect events because they are not on the leeward shore of a lake during a northwest wind. However Toronto and Hamilton are close enough to Georgian Bay and Lake Huron that they receive small amounts of lake effect snow each winter. Even so, an unusual easterly or northeasterly wind can deposit heavy shows on Chicago or Milwaukee much as a northwesterly winter wind on the opposite side of Lake Michigan.
[edit] Phenomenon elsewhere in United States
The southern and southeastern sides of the Great Salt Lake also receive significant lake effect snow. The Finger Lakes of New York also are long enough for lake effect precipitation.
[edit] Similar phenomena
Similar snowfall can occur near large inland bays, where it is known as Bay effect snow. Bay-effect snows fall downwind of Delaware Bay, Chesapeake Bay, and Massachusetts Bay when the basic criteria are met. Ocean effect snows are possible downwind from continental land mass passing over open waters<ref>Lake Effect-type Phenomena in Other Regions. by COMET Retrieved on 2006-11-05.</ref>. Canadian Maritimes, in particular Nova Scotia and Prince Edward Island provinces, are often affected by such snowsqualls when an arctic winter airmass moves over unfrozen waters. This effect is especially intense with very warm waters of the Gulf Stream or the Sea of Japan. An extreme occurrence of "ocean effect" snow occurred on January 24, 2003, when wind off the Atlantic, combined with air temperatures in the 20s (°F), brought snow flurries to the Atlantic coast of Florida as far south as Cape Canaveral. <ref>National Weather Serivce Office, Melbourne, Florida. Cold Temperatures and Snow Flurries in East-Central Florida January 24, 2003. Retrieved on 2006-11-05.</ref>.
A phenomenon similar to the lake effect snow may also occur in other countries, nearby large lakes or sea regions. An example is the Aegean Sea in Greece, where cold Southeast wind often produces heavy snowfalls over Euvia and Northen parts of Athens, with duration of 3 days up to 1 week and snowcover of 40 inches or more. Similar effects also occur in Black Sea and Turkey or Adriatic Sea and Italy.
[edit] References
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[edit] See also
Warnings about lake effect snow:
United States
Canada:
