Lake effect snow

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Lake effect snow, which can be a type of snowsquall, is produced in the winter when cold, arctic dry 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 each hour and often bringing copious snowfall totals. The areas affected by lake effect snow are called snowbelts. This effect occurs in many locations throughout the world, mostly in the Northern Hemisphere, but is best known in the populated areas of the Great Lakes of North America. The lake effect from the Great Salt Lake in Utah helps to create "The Greatest Snow on Earth". Since the Great Salt Lake never freezes, the lake effect can affect the weather along the Wasatch front year around.

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 moving air must be cooler and also less humid than the surface air. Specifically, the air temperature should be 15 to 25°C cooler than the water, and the dew point at the altitude where the air pressure is 850 mb should be 13°C lower than the dew point of the air at the surface. Lake effect of extremely cold air over still warm water in early winter can produce thundersnow, snow showers accompanied by lightning and thunder.

Contents 1 Cause 2 Phenomenon in northeast United States 3 Phenomenon elsewhere in United States 4 Similar phenomena 5 References 6 See also 6.1 External links

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.^[1] 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.^[2]

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. Syracuse, New York is directly south of the Tug Hill Plateau and receives significant lake effect snow from Lake Ontario (although less than the Tug Hill Plateau by as much as 200 inches (508 cm)). In fact, Syracuse receives so much snowfall it is often considered the "snowiest" large city in America, averaging 115.6" (293.6 cm) of snow a year. Syracuse has frequently won the "Golden Snowball" award, a NOAA regional contest for greatest annual snowfall among large Upstate New York snowbelt cities. The communities of Redfield, in Oswego County and Montague and North Osceola, in Lewis County, all on the Tug Hill Plateau, average over 300 inches (762 cm) of snow a winter, with more than 400 inches (1,016 cm) falling during harsh winters. A 24 hour record for the contiguous United States occurred on January 11th-12th 1997 when 77" (196 cm) of snow fell in Montague NY, a total of 95 inches (241 cm) of snow fell in that storm between the 11th and 14th. (Source, National Weather Service, Buffalo.) 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, with a southern limit around Pittsburgh. Remnants of lake effect snows from Lake Erie have been observed to reach Garrett County in western Maryland. Lake Erie has the distinction of being the only great lake to completely freeze during the winter as a result of being very shallow, although this does not happen every winter. Once frozen, the resulting ice cover temporarily alleviates lake effect snow from originating there.

Another snowbelt is in the Upper Peninsula (UP) of Michigan, near the cities of Houghton, Marquette, and Munising. These areas frequently average over 200 inches (508 cm), and may receive close to 300 inches (762 cm) of snow a year (for comparison, on the western shore, Duluth, Minnesota receives only 77 inches (196 cm)). 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. This band produced 8 inches (20 cm) of snow in the eastern and northern suburbs of Toronto affecting places such as King City and Markham. 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, a less frequent easterly or northeasterly wind can deposit heavy snows on Chicago or Milwaukee much as a northwest/westerly wind does for the opposite side of Lake Michigan.

In February, 2007 a prolonged lake effect snow event left over 100 inches (254 cm) of snow on the Tug Hill Plateau.^[3]

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. The twin cities of Sherman, Texas and Denison, Texas are also known to have experienced lake effect snow from Lake Texoma in rare instances.

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 of the Gulf Stream and the Sea of Japan.^[4] 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. This also happens usually a couple of times per winter in the area near Cape Cod and on rarer occasions along Long Island. An extreme occurrence of "ocean effect" snow occurred on January 24, 2003, when wind off the Atlantic, combined with air temperatures in the 20 °F (-6.6 °C), brought snow flurries to the Atlantic coast of Florida as far south as Cape Canaveral.^[5]

A phenomenon similar to lake effect snow may also occur in other countries, near large lakes or sea regions. One example is the Aegean Sea in Greece, where cold northeast winds known as the boreas can produce heavy snowfalls over Euvia and Northern parts of Athens. These systems can have a duration of 3 days to 1 week and result snowcover of 40 inches (101.6 cm) or more. Similar effects also occur in the regions of the Black Sea and Turkey or the Adriatic Sea and Italy. A cold, dry airmass from Sweden can blow over the Baltic Sea and cause heavy snow squalls on areas of the southern and eastern coasts.

References

See also

Template:Commons Warnings about lake effect snow:

United States:

• Lake Effect Snow Advisory
• Lake Effect Snow Warning
• Severe weather terminology (United States)

Canada:

• Snowsquall warning
• Severe weather terminology (Canada)

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