Lake-effect snow 43864 214203094 2008-05-22T15:12:13Z OliAtlason 212420 [[WP:UNDO|Undid]] revision 214197898 by [[Special:Contributions/216.120.170.163|216.120.170.163]] ([[User talk:216.120.170.163|talk]]) [[Image:October 12-13 radarloop kbuf.gif|thumb|250px|Lake-effect precipitation coming off [[Lake Erie]], as seen by [[NEXRAD]] radar, [[Lake Storm "Aphid"|October 12-13, 2006]] ]] '''Lake-effect snow''' is produced in the winter when cold, Arctic winds move across long expanses of warmer lake water, providing energy and picking up [[water vapor]] which freezes and is deposited on the [[lee shore]]s. The same effect over bodies of salt water is called '''ocean effect snow''', '''sea effect snow''', or even '''bay effect snow'''. The effect is enhanced when the moving air mass is uplifted by the [[orographic lift|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 [[snowbelt]]s. This effect occurs in many locations throughout the world, but is best known in the populated areas of the [[Great Lakes]] of [[North America]]. 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 air moving across the lake must be significantly cooler than the surface air (which is likely to be near the temperature of the water surface). Specifically, the air temperature at the altitude where the [[air pressure]] is 850 [[millibars]] (roughly 1.5 vertical kilometers) should be 13°C lower than the temperature of the air at the surface. Lake-effect occurring when the air at 850 [[millibars]] is much colder than the water surface can produce [[thundersnow]], snow showers accompanied by [[lightning]] and [[thunder]] (due to the larger amount of energy available from the increased instability). ==Formation== [[Image:Lake-derived-snow.svg|thumb|250px|right|Lake-effect snow produced as cold winds blow clouds over warm waters.]] There are several key ingredients that are required to form lake effect precipitation, and which determine its characteristics: instability, fetch, wind shear, upstream moisture, upwind lakes, synoptic (large)-scale forcing, orography/topography, and snow or ice cover. ===Instability=== A temperature difference of 13°C between the lake temperature and 850 millibar level, or {{convert|1500|m|ft}} above sea level, provides for absolute instability and allows vigorous heat and moisture transportation vertically. Atmospheric lapse rate and convective depth are directly affected by both the mesoscale lake environment and the synoptic environment; a deeper convective depth with increasingly steep lapse rates and a suitable moisture level will allow for thicker, taller lake effect precipitation clouds and naturally a much greater precipitation rate.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld010.htm Instability<!-- Bot generated title -->]</ref> ===Fetch=== The distance that an airmass travels over a body of water is called its fetch. Because most lakes are irregular in shape, different angular degrees of travel will yield different distances; typically a fetch of at least 100 km is required to produce lake effect precipitation. Generally, the larger the fetch the more precipitation that will be produced. Larger fetches provide the boundary layer with more time to become saturated with water vapor, and for heat energy to move from the water to the air.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld012.htm Fetch<!-- Bot generated title -->]</ref> [[Image:Lake effect snow wind direction bands1.gif|thumb|left|The location of common lake effect bands on the Great Lakes]] ===Wind shear=== Directional shear is one of the most important factors governing the development of squalls, environments with weak directional shear typically produce more intense squalls than those with higher shear levels. If directional shear between the surface and 700mb level is greater than 60 degrees, nothing more than flurries can be expected at the most. If the directional shear between the surface and 700mb level is between 30 and 60 degrees weak lake effects bands are possible. In environments where the shear is less than 30 degrees strong, well organized bands can be expected.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld014.htm Wind Shear<!-- Bot generated title -->]</ref> Speed shear unlike directional shear is less critical but it should be relatively uniform. The wind speed difference between the surface and 700mb level should be no greater than 40 knots so as to prevent the upper portions of the band from shearing off. However assuming the surface to 700mb winds are uniform, a faster overall velocity will work to transport moisture quicker from the water and the band will travel much further inland.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld014.htm Wind Shear<!-- Bot generated title -->]</ref> [[Image:Lake effect deltat chart.gif|thumb|right|Temperature difference and instability are directly related, the greater the difference the more unstable and convective the lake effect precipitation will be.]] ===Upstream moisture=== A lower upstream relative humidity will make it more difficult and time consuming for lake effect condensation, cloud and precipitation to form. The opposite is true if the upstream moisture has a high relative humidity allowing lake effect condensation, cloud and precipitation to form more quickly and in a greater quantity.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld015.htm Upstream Moisture<!-- Bot generated title -->]</ref> ===Upwind lakes=== Any large body of water upwind will impact lake effect precipitation to the lee of a downwind lake by adding moisture or pre-existing lake effect bands which can re-intensify over the downwind lake. It should be noted though that upwind lakes do not always lead to an increase of precipitation downwind.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld016.htm Upstream Lakes<!-- Bot generated title -->]</ref> ===Synoptic forcing=== Vorticity advection aloft and large upscale ascent help increase mixing and the convective depth, while cold air advection lowers the temperature and increases instability.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld019.htm Synoptic-Scale Forcing<!-- Bot generated title -->]</ref> ===Orography and topography=== Typically lake effect precipitation will increase with elevation to the lee of the lake as topographic forcing squeezes out precipitation and dries out the squall much faster.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld021.htm Orography/Topography<!-- Bot generated title -->]</ref> ===Snow and ice cover=== As a lake gradually freezes over its ability to produce lake effect precipitation decreases for two reasons. Firstly, the open ice free liquid surface area of the lake shrinks reducing fetch distances while secondly, the water temperature nears freezing reducing the overall latent heat energy available to produce squalls. In order to end the production of lake effect precipitation, a complete freeze is often not necessary.<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld022.htm Snow/Ice Cover on the Great Lakes<!-- Bot generated title -->]</ref> Even when precipitation is not produced, cold air passing over warmer water may produce cloud cover. Fast moving mid latitude cyclones, known as [[Alberta clipper]]s 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. 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.<ref>[http://www.wunderground.com/health/mood.asp : Weather Underground<!-- Bot generated title -->]</ref> ==Phenomenon in the Great Lakes region, Southeast Canada and the U.S. Northeast== [[Image:Buffalo2001-20.jpg|thumb|right|[[Buffalo, New York|Buffalo, NY]] after 82.3 inches (209 cm) of snow fell from [[December 24]], [[2001]] to [[December 28]], [[2001]].]] 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 (North America)|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, averaging {{convert|115.6|in|cm}} of snow a year, which is enough snowfall to often be considered the "snowiest" large city in America.<ref>Cappella, Chris: "[http://www.usatoday.com/weather/resources/askjack/2003-10-01-snowiest-cities_x.htm Answers: 10 snowiest 'cities' aren't all in New York]", ''[[USA Today]]'', [[3 October]] [[2003]]</ref><ref>Kirst, Sean: "We won't buckle under the Snowbelt's blows", ''[[Post-Standard]]'', [[14 March]] [[2005]]</ref> The communities of [[Redfield, New York|Redfield]] in [[Oswego County]] and [[Montague, New York|Montague]] and [[Osceola, New York|North Osceola]] in [[Lewis County, New York|Lewis County]], all on the [[Tug Hill Plateau]], average over {{convert|300|in|cm}} of snow a winter.<ref>Northern Forest Alliance. [http://www.northernforestalliance.org/explore/wildlands/tughill/TUGindex.htm Tug Hill Plateau - New York.] Retrieved on [[2008-03-01]].</ref> In February, 2007, a prolonged lake-effect snow event left {{convert|141|in|cm}} of snow on the Tug Hill Plateau.<ref>[[National Climatic Data Center]]. [http://www.ncdc.noaa.gov/oa/climate/research/2007/feb/feb07.html Climate of 2007 - February in Historical Perspective.] Retrieved on [[2008-03-01]].</ref> Lake-effect snow from the [[Finger Lakes]] occurs in upstate New York 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, Ohio|Cleveland]] to [[Erie, Pennsylvania|Erie]] to [[Buffalo, New York|Buffalo]].<ref name="SCHMID">Thomas W. Schmidlin. [https://kb.osu.edu/dspace/bitstream/1811/23329/1/V089N4_101.pdf Climatic Summary of Snowfall and Snow Depth in the Ohio Snowbelt at Chardron.] Retrieved on [[2008-03-01]].</ref> Remnants of lake-effect snows from Lake Erie have been observed to reach as far as [[Garrett County]] in western [[Maryland]].<ref>Northeast Regional Climate Center. [http://www.nrcc.cornell.edu/climate/Impacts_02-95.html February Brings Winter Weather to the Northeast.] Retrieved on [[2008-03-01]].</ref> The Canadian lake effect belt spans from Port Stanley in the west, Brantford in the north, Niagara-on-the-Lake to the northeast and Fort Erie to the south, with the cities of Nanticoke, Dunnville, Port Colborne and Fort Erie seeing the greatest accumulations. Lake Erie has the distinction of being the only great lake capable of completely freezing over during the winter due to its relative shallowness.<ref>Great Lakes Information Network. [http://www.great-lakes.net/teach/geog/intro/intro_6.html 6 | Introduction to the Great Lakes.] Retrieved on [[2008-03-01]].</ref> Once frozen, the resulting ice cover alleviates lake-effect snow downwind of the lake. [[Image:Sat1.gif|thumb|250px|Visible Satellite image showing a large single lake-effect band with vigorous vertical motion. This band produced 8 inches (20 cm) of snow in the eastern and northern suburbs of [[Toronto]].]] Another [[snowbelt]] is in the [[Upper Peninsula of Michigan|Upper Peninsula (UP)]] of [[Michigan]], near the cities of [[Houghton, Michigan|Houghton]], [[Marquette, Michigan|Marquette]], and [[Munising, Michigan|Munising]]. These areas average over {{convert|200|in|cm}} of snow a season.<ref>Robert J. Ruhf. [http://www.x98ruhf.net/lake_effect.htm Lake-Effect Precipitation in Michigan.] Retrieved on [[2008-03-01]].</ref> For comparison, on the western shore, [[Duluth, Minnesota]] receives {{convert|78|in|cm}} per season.<ref>[[University of Utah]] Department of Meteorology. [http://www.met.utah.edu/jhorel/html/wx/climate/normsnow.html Average Snowfall, Inches.] Retrieved on [[2008-03-01]].</ref> [[Lake Superior]] and [[Lake Huron]] rarely freeze due to their size and depth; lake-effect snow can fall continually in the Upper Peninsula and the [[Ontario]], [[Canada]] snowbelts during the winter months. There are 4 distinct Lake Huron snow belts that exist in Ontario, the first spans from Sarnia to Grand Bend, with cities as far south as London sometimes receiving significant accumulations. The second spans from Grand Bend to Owen Sound and north to Tobermory with significant snows often affecting regions as far south as Arthur, Orangeville and Caledon. Under extremely unstable conditions significant snows may reach Kitchener, Guelph and western portions of Halton and Peel Regions. The third distinct belt spans from Owen Sound in the West to Cannington in the East, and Gravenhurst to the North, with significant snows often affecting the cities of Barrie and Orillia and to a lesser degree northern portions of York Region, such as Newmarket, Aurora and King City. The fourth belt spans from Noelville which is 50 km south of Sudbury to Gravenhurst, and as far East as [[Highway 62 (Ontario)|Hwy. 62]], with strong streamers often reaching into Algonquin Park. Lake Superior has its own series of Canadian snow belts, the first spanning from Wawa to Sault Ste. Marie with streamers travelling as far east as [[Highway 129 (Ontario)|Hwy. 129]]. The second belt spans from Marathon to Wawa with Pukaskwa National Park receiving the majority of the precipitation. Sault Ste. Marie. [[Western Michigan]], western [[Northern Michigan|Northern Lower Michigan]], and [[Northern Indiana]] can get heavy lake-effect snows as winds pass over Lake Michigan and deposit snows over [[Traverse City, Michigan|Traverse City]], [[Grand Rapids, Michigan|Grand Rapids]], [[Kalamazoo, Michigan|Kalamazoo]], and [[South Bend, Indiana|South Bend]], but these snows abate significantly before [[Lansing, Michigan|Lansing]] or [[Fort Wayne, Indiana]]. [[Image:Wasaga Beach 60 cm snow 12 hours Jan04 02.JPG|thumb|left|200px|The community of [[Wasaga Beach]] after sixty centimeters of snow fell in 12 hours from a persistent lake effect band]] Cities such as [[Toronto]], [[Hamilton, Ontario|Hamilton]], [[Detroit, Michigan|Detroit]], [[Milwaukee, Wisconsin|Milwaukee]], and [[Chicago]] frequently miss out on lake-effect events because they are not on the leeward shore of a lake during the predominant northwest wind seen during many lake effect events. However Toronto and Hamilton are close enough to [[Georgian Bay]] and [[Lake Huron]] that they receive small amounts of lake-effect snow each winter with a typical westerly or north-westerly wind. Nevertheless, both cities have received significant accumulations resulting from rare easterly and south-easterly winds, usually associated with northern potions of winter cyclones and sometimes southern portions of anti-cyclones that can generate snow squalls from [[Lake Ontario]]. 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. ==Phenomenon elsewhere in the United States== <!-- Deleted image removed: [[Image:Lake Effect snow off Great Salt Lake.jpg|thumb|right|Satellite image of lake effect snow coming off of the Great Salt Lake and into Salt Lake City, Utah.]] --> [[Image:Fultonles.jpg|thumb|right|Fulton, New York after a snowburst dropped 4-6 feet of snow over most of Oswego County between January 28-31, 2004.]] The southern and southeastern sides of the [[Great Salt Lake]] receive significant lake-effect snow. Since the Great Salt Lake never freezes, the lake-effect can affect the weather along the [[Wasatch Front]] year around. The lake-effect largely contributes to the 55-80 inch (140-200 cm) annual snowfall amounts recorded south and east of the lake, and in average snowfall reaching 500 inches (1,270 cm) in the [[Wasatch Range]]. The snow, which is often very light and dry due to the desert climate, is referred to as "The Greatest Snow on Earth" in the mountains. Lake-effect snow contributes to approximately 6-8 snowfalls per year in Salt Lake City, with approximately 10% of the city's precipitation being contributed by the phenomenon.<ref>[http://deseretnews.com/misc/gsl/105002200.htm Deseret Morning News - Lake has great impacts on storm, weather]. [[August 5]], [[1999]].</ref> 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. The West Coast occasionally experiences ocean-effect showers, usually in the form of rain at lower elevations south of about the mouth of the [[Columbia River]]. These occur whenever an Arctic air mass from western Canada is drawn westward out over the Pacific Ocean, typically by way of the [[Fraser Valley]], returning shoreward around a center of low pressure. ==Phenomenon elsewhere in Canada== [[Lake Winnipeg]] and [[Lake Winnipegosis]] in [[Manitoba]] traditionally see lake effect snow as early as late October and it is common throughout early to mid November. Towards the end of November the lakes sufficiently cool and begin to freeze ending the lake effect snow. A brief period of lake effect snow is also common near [[Great Bear Lake]] and [[Great Slave Lake]] in the [[Northwest Territories]] during early winter (usually early to mid October), however the lake effect season for both lakes is very short. Due to their northern location the lakes are frozen roughly 8 months of the year and as a result have very little time to warm during the summer months. Other small lakes such as [[Lake Athabasca]] in Northern [[Saskatchewan]] and [[Lake Nipigon]] in Northwestern [[Ontario]] also produce early season lake effect snows. The [[Smallwood Reservoir]], a man made lake located in [[Labrador]] has on occasion also generated lake effect snow. ==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]].<ref>[http://www.comet.ucar.edu/class/smfaculty/byrd/sld003.htm Lake Effect-type Phenomena in Other Regions.] by [http://www.comet.ucar.edu/ 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]]. 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]].<ref>National Weather Service Office, Melbourne, Florida. [http://www.srh.noaa.gov/mlb/surveys/012403/flurries.html Cold Temperatures and Snow Flurries in East-Central Florida January 24, 2003.] Retrieved on 2006-11-05.</ref> ==International phenomena== [[Image:Snow-chart.png|thumb|right|Chart showing the lake-effect snow event of January 1987 in the UK. A continuous stream of showers deposited over a foot of snow over SE coastal regions.]] A phenomenon similar to lake-effect snow may also occur in other countries, near large lakes or large sea areas. One such example is the [[Aegean Sea]] in [[Greece]], where cold northeast winds known as the [[Anemoi#North wind .28Boreas.29|boreas]] combined with the sea moisture can produce very heavy snowfalls over [[Athens]] (particularly across the mountainous northern suburbs of the city), the island of [[Euboea]] and easternmost [[Peloponese]]. These intense systems can have a duration of 2 to 5 days and result to a snowcover of 40 inches (101.6 cm) or more. One such system, that occurred between January 4 and January 7, 2002, wreaked havoc across that entire area, essentially shutting down Athens. Similar effects also occur in the regions of the Black Sea in [[Georgia (country)|Georgia]] and [[Turkey]] or the Adriatic Sea and [[Italy]]. The snowfall in the eastern regions of the Black Sea is amplified by the orographic effect of the nearby [[Caucasus Mountains]], often resulting in snowfall of several meters, especially at higher elevations. In Northern Europe, cold, dry airmasses from Sweden can blow over the [[Baltic Sea]] and cause heavy snow squalls on areas of the southern and eastern coasts. In the [[United Kingdom]], easterly winds bringing cold Continental air across the [[North Sea]] can lead to a similar phenomenon. Locally it is also known as "lake-effect snow" despite the snow coming in from the sea rather than a lake. <ref>USW archives [http://groups.google.co.uk/groups/search?hl=en&ie=UTF-8&oe=UTF-8&q=%22lake+effect+snow%22+%22north+sea%22group%3Auk.sci.weather&qt_s=Search] Retrieved on 2007-08-03.</ref> Similarly during a north-westerly wind, snow showers can form coming in from the [[Liverpool Bay]], coming down the [[Cheshire gap]], causing snowfall in the [[West Midlands (region)|West Midlands]]. This formation resulted in the white Christmas of [[2004]], in the area. Due to the North Sea being relatively warm (around 13C at the beginning of winter, typically 10C to 6C by the end), sufficiently cold air aloft can create significant snowfalls in a relatively short period of time. The best-known example occurred in January 1987, when record-breakingly cold air (associated with an upper low) moved across the North Sea towards the UK. The end result was over a foot of snow for coastal areas, leading to communities being cut off for over a week. In recent years lake-effect snow has been much lighter, due to a lack of very cold Continental easterlies. ==Notable lake-effect episodes== * [[Lake Storm "Aphid"]]: [[October 12]] – [[October 13|13]], [[2006]] - A crippling lake effect storm which struck Buffalo New York and surrounding areas with nearly 60cm of heavy wet snow, damaging many trees (most of which were still in full leaf) and knocking out power. * [http://www.erh.noaa.gov/er/buf/lakeffect/lake0102/b/stormb.html Lake Effect Storm Bald Eagle]: [[December 24]], [[2001]] – [[January 1]], [[2002]] - A major several day event in which Buffalo NY sees over 80 inches of snow. This event is even featured in local postcards. ==References== {{reflist}} ==See also== {{Commons|Lake effect snow}} *[[Great Salt Lake effect]] 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)]] ==External links== *[http://www.erh.noaa.gov/buf/lakeffect/indexlk.html National Weather Service Official Lake Effect Page] - Based in Buffalo, NY *[http://www.theweatherprediction.com/winterwx/lesnow/ Lake effect forecasting] *[http://www.goldensnowball.com The Golden Snowball Award website] *[http://www.vaughanweather.com/winter/ Canadian Snowsquall storm chaser] *[http://wintercenter.homestead.com/photoles2001a.html Digital Snow Museum] *[http://www.youtube.com/watch?v=Hd6DuebHliY A BBC forecast of lake effect snow in the UK in 1991] [[Category:Snow or ice weather phenomena]] [[Category:Snow]] [[Category:Climate forcing agents]] [[Category:Upper Peninsula of Michigan]] [[de:Lake effect snow]] [[fr:Bourrasque de neige]] [[fi:Avoveden vaikutus lumisateeseen]] [[zh:大湖效應]]