Editing Snow (section)

===Cloud formation===
Snow clouds usually occur in the context of larger weather systems, the most important of which is the low-pressure area, which typically incorporates warm and cold fronts as part of its circulation. Two additional and locally productive sources of snow are lake-effect (also sea-effect) storms and elevation effects, especially in mountains.

====Low-pressure areas====
{{Main|Extratropical cyclone}}
[[File:Feb242007 blizzard.gif|thumb|right|Extratropical cyclonic snowstorm, February 24, 2007—(Click for animation.)]]

[[Extratropical cyclone|Mid-latitude cyclones]] are [[low-pressure area]]s which are capable of producing anything from cloudiness and mild [[Winter storm#Snow|snow storms]] to heavy [[blizzard]]s.<ref name="ExtraLessonMillUni">{{cite web| title = ESCI 241&nbsp;– Meteorology; Lesson 16&nbsp;– Extratropical Cyclones | author = DeCaria| publisher = Department of Earth Sciences, [[Millersville University]]| date = December 7, 2005| url = http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html | access-date = June 21, 2009 |archive-url = https://web.archive.org/web/20080208224320/http://www.atmos.millersville.edu/~adecaria/ESCI241/esci241_lesson16_cyclones.html |archive-date = February 8, 2008}}</ref>  During a hemisphere's [[autumn|fall]], winter, and spring, the atmosphere over continents can be cold enough through the depth of the [[troposphere]] to cause snowfall. In the Northern Hemisphere, the northern side of the low-pressure area produces the most snow.<ref>
{{cite journal
 |last        = Tolme
 |first       = Paul
 |title       = Weather 101: How to track and bag the big storms
 |journal     = Ski Magazine
 |volume      = 69
 |issue       = 4
 |page       = 126
 |date        = December 2004
 |url         = https://books.google.com/books?id=t1DaXO7wF20C&pg=PA126
 |issn        = 0037-6159
 }}</ref> For the southern [[mid-latitudes]], the side of a [[cyclone]] that produces the most snow is the southern side.

====Fronts====
{{Main|Weather front}}
[[File:Snowsquall line-Bourrasque neige frontal NOAA.png|thumb|right|Frontal snowsquall moving toward [[Boston]], [[Massachusetts]]]]
A [[cold front]], the leading edge of a cooler mass of air, can produce [[Snowsquall#Frontal snowsquall|frontal snowsqualls]]—an intense frontal [[convective]] line (similar to a [[rainband]]), when [[temperature]] is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which the line passes over as the wind causes intense blowing snow.<ref name=EC-2>{{Cite web
 |url         = http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=46FBA88B-1#Snow
 |title       = Snow
 |work        = Winter Hazards
 |author      = Meteorological Service of Canada
 |author-link = Meteorological Service of Canada
 |publisher   = [[Environment Canada]]
 |date        = September 8, 2010
 |access-date  = October 4, 2010
 |url-status=live
 |archive-url  = https://web.archive.org/web/20110611163137/http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=46FBA88B-1#Snow
 |archive-date = June 11, 2011
 |df          = mdy-all
}}</ref> This type of snowsquall generally lasts less than 30 minutes at any point along its path, but the motion of the line can cover large distances. Frontal squalls may form a short distance ahead of the surface cold front or behind the cold front where there may be a deepening low-pressure system or a series of [[Trough (meteorology)|trough]] lines which act similar to a traditional cold frontal passage. In situations where squalls develop post-frontally, it is not unusual to have two or three linear squall bands pass in rapid succession separated only by {{convert|25|mi|km|abbr=off|sp=us}}, with each passing the same point roughly 30 minutes apart. In cases where there is a large amount of vertical growth and mixing, the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed [[thundersnow]].

A [[warm front]] can produce snow for a period as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Often, snow transitions to rain in the warm sector behind the front.<ref name=EC-2/>

====Lake and ocean effects====
{{Main|Lake-effect snow}}
[[File:Lake Effect Snow on Earth.jpg|thumb|Cold northwesterly wind over [[Lake Superior]] and [[Lake Michigan]] creating lake-effect snowfall]]

Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer [[lake]] water, warming the lower layer of air which picks up [[water vapor]] from the lake, rises up through the colder air above, freezes, and is deposited on the [[leeward]] (downwind) shores.<ref>{{cite web|url=http://www.noaa.gov/features/02_monitoring/lakesnow.html|title=NOAA - National Oceanic and Atmospheric Administration - Monitoring & Understanding Our Changing Planet|url-status=live|archive-url=https://web.archive.org/web/20150102173430/http://www.noaa.gov/features/02_monitoring/lakesnow.html|archive-date=January 2, 2015|df=mdy-all}}</ref><ref>{{cite web|url=http://www.comet.ucar.edu/class/smfaculty/byrd/sld012.htm |title=Fetch |url-status=dead |archive-url=https://web.archive.org/web/20080515101954/http://www.comet.ucar.edu/class/smfaculty/byrd/sld012.htm |archive-date=May 15, 2008 }}</ref>

The same effect occurring over bodies of salt water is termed ''ocean-effect'' or ''bay-effect snow''. The effect is enhanced when the moving air mass is uplifted by the [[orographic lift|orographic]] influence of higher elevations on the downwind shores. This uplifting can produce narrow but very intense bands of precipitation which may deposit at a rate of many inches of snow each hour, often resulting in a large amount of total snowfall.<ref name=mass>{{cite book |last= Mass |first= Cliff |title= The Weather of the Pacific Northwest |year= 2008 |publisher= [[University of Washington Press]] |isbn= 978-0-295-98847-4 |page= 60}}</ref>

The areas affected by lake-effect snow are called [[snowbelt]]s. These include areas east of the [[Great Lakes]], the west coasts of northern Japan, the [[Kamchatka Peninsula]] in Russia, and areas near the [[Great Salt Lake]], [[Black Sea]], [[Caspian Sea]], [[Baltic Sea]], and parts of the northern Atlantic Ocean.<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 Chardon.] {{webarchive|url=https://web.archive.org/web/20080408225438/https://kb.osu.edu/dspace/bitstream/1811/23329/1/V089N4_101.pdf |date=April 8, 2008 }} Retrieved on March 1, 2008.</ref>

====Mountain effects====
{{Main|Precipitation types#Orographic}}
[[Orography|Orographic]] or [[relief]] snowfall is created when moist air is forced up the [[windward]] side of [[mountain]] ranges by a large-scale [[wind]] flow. The lifting of moist air up the side of a mountain range results in [[Adiabatic lapse rate|adiabatic]] cooling, and ultimately [[condensation]] and precipitation. Moisture is gradually removed from the air by this process, leaving [[Foehn wind|drier and warmer air]] on the descending, or [[leeward]], side.<ref name="MT">Physical Geography. [http://www.physicalgeography.net/fundamentals/8e.html CHAPTER 8: Introduction to the Hydrosphere (e). Cloud Formation Processes.] {{webarchive|url=https://web.archive.org/web/20081220230524/http://www.physicalgeography.net/fundamentals/8e.html |date=December 20, 2008 }} Retrieved on January 1, 2009.</ref> The resulting enhanced snowfall,<ref>{{Citation
 |first1        = Mark T.
 |last1         = Stoelinga
 |first2       = Ronald E.
 |last2        = Stewart
 |first3       = Gregory
 |last3        = Thompson
 |first4       = Julie M.
 |last4        = Theriault
 |editor-last  = Chow
 |editor-first = Fotini K.
 |display-editors=1
 |editor2=Stephan F.J. De Wekker
 |editor3=Bradley J. Snyder
 |title        = Mountain Weather Research and Forecasting: Recent Progress and Current Challenges
 |contribution = Micrographic processes within winter orographic cloud and precipitation systems
 |series       = Springer Atmospheric Sciences
 |year         = 2012
 |page         = 3
 |publisher    = Springer Science & Business Media
 |bibcode = 2013mwrf.book.....C
 |url          = https://books.google.com/books?id=ihjFd5Q8oPMC&pg=PA3
 |isbn         = 978-94-007-4098-3
 }}</ref> along with the [[Lapse rate|decrease in temperature]] with elevation,<ref>{{cite book|author=Mark Zachary Jacobson|title=Fundamentals of Atmospheric Modeling|publisher=Cambridge University Press|edition=2nd|year=2005|isbn=978-0-521-83970-9}}</ref> combine to increase snow depth and seasonal persistence of snowpack in snow-prone areas.<ref name = Snowenclyclopedia/><ref name=Singh>
{{cite book
 |last        = P.
 |first       = Singh
 |title       = Snow and Glacier Hydrology
 |publisher   = Springer Science & Business Media
 |series      = Water Science and Technology Library
 |volume      = 37
 |date        = 2001
 |page        = 75
 |url         = https://books.google.com/books?id=0VW6Tv0LVWkC&pg=PA75
 |isbn        = 978-0-7923-6767-3
 }}</ref>

[[Mountain waves]] have also been found to help enhance precipitation amounts downwind of mountain ranges by enhancing the lift needed for condensation and precipitation.<ref>{{cite journal|last1=Gaffin|first1=David M.|last2=Parker|first2=Stephen S.|last3=Kirkwood|first3=Paul D.|date=2003|title=An Unexpectedly Heavy and Complex Snowfall Event across the Southern Appalachian Region|journal=Weather and Forecasting|volume=18|issue=2|pages=224–235|bibcode=2003WtFor..18..224G|doi=10.1175/1520-0434(2003)018<0224:AUHACS>2.0.CO;2|doi-access=free}}</ref>