Editing Thundersnow

{{short description|Thunderstorm during which there is snowfall}}
{{Use mdy dates|date=July 2023}}<!--Predominant date format per MOS:DATEUNIFY-->
{{about|the weather phenomenon|the racehorse|Thunder Snow|the sports team|Western New York Thundersnow}}
[[File:Occludedfront.gif|thumb|400px|right|Thundersnow formation with an [[occluded front]]]]
{{Weather}}
'''Thundersnow''', also known as a '''winter thunderstorm''' or a '''thundersnow storm''', is a [[thunderstorm]] in which [[snow]] falls as the primary [[precipitation (meteorology)|precipitation]] instead of [[rain]]. It is considered a rare phenomenon.<ref>{{Cite web|last=Coulter |first=Dauna |title=The Mysterious Rumble of Thundersnow |publisher=[[NASA]] |website=NASA Science |date=24 February 2011 |url=https://science.nasa.gov/science-news/science-at-nasa/2011/24feb_thundersnow/ |access-date=21 July 2023 |archive-date=27 January 2019 |archive-url=https://web.archive.org/web/20190127102231/https://science.nasa.gov/science-news/science-at-nasa/2011/24feb_thundersnow/ |url-status=live}}</ref> It typically falls in regions of strong upward motion within the cold sector of an [[extratropical cyclone]]. Thermodynamically, it is not different from any other type of thunderstorm, but the top of the [[cumulonimbus|cumulonimbus cloud]] is usually quite low. In addition to snow, [[graupel]] or [[hail]] may fall as well. The heavy snowfall tends to muffle the sound of the thunder so that it sounds more like a low rumble than the loud, sharp bang that is heard during regular thunderstorms.<ref name=cnn>{{cite web |title=Thundersnow is a rare weather phenomenon. Here's what you need to know |website=[[CNN.com]] |first1=Brandon |last1=Miller |first2=Zoe |last2=Sottile |date=18 November 2022 |url=https://www.cnn.com/2022/11/18/weather/thundersnow-explainer-xpn/index.html}}</ref>

Thundersnow can occur during a normal snowstorm that sustains strong vertical mixing which allows for favorable conditions for [[lightning]] and [[thunder]] to occur. It can also occur from the [[lake-effect snow|lake effect]] or ocean effect thunderstorm which is produced by cold air passing over relatively warm water; this effect commonly produces [[snow squall]]s over the [[Great Lakes]].

==Occurrence==
{{More citations needed section|date=July 2023}}
===Americas===
Within the United States, thundersnow is relatively rare but most common in "eastern [[Nevada]] and [[Utah]], the [[Great Plains|central plains]], and the [[Great Lakes region|Great Lake]] {{sic}} states".<ref>{{Cite journal |title=A Climatology of Thundersnow Events over the Contiguous United States |url=https://journals.ametsoc.org/view/journals/wefo/17/6/1520-0434_2002_017_1290_acoteo_2_0_co_2.xml |journal=[[Weather and Forecasting]] |publisher=[[American Meteorological Society]] |date=1 December 2002 |first1=Patrick S. |last1=Market |first2=Chris E. |last2=Halcomb |first3=Rebecca L. |last3=Ebert |volume=17 |issue=6 |page=1290 |doi=10.1175/1520-0434(2002)017<1290:ACOTEO>2.0.CO;2 |doi-access= |bibcode=2002WtFor..17.1290M |access-date=21 July 2023 |archive-url=https://web.archive.org/web/20230506065905/https://journals.ametsoc.org/view/journals/wefo/17/6/1520-0434_2002_017_1290_acoteo_2_0_co_2.xml |archive-date=6 May 2023 |url-status=live|url-access=subscription }}</ref> Thundersnow also occurs in [[Nova Scotia]] and in the [[Northeastern United States]], especially in [[New England]] and [[New York (state)|New York]], sometimes several times per winter season.{{Citation needed|date=July 2023}} On December 30, 2019, a [[severe thunderstorm warning]] was issued for parts of [[Massachusetts]] for a thunderstorm cell that was producing "lightning, thundersnow, thundersleet, and thunderice".<ref>{{Cite web|url=https://www.masslive.com/weather/2019/12/thundersnow-hail-and-lightning-reported-during-ice-storm-thunderstorm-warning-issued-in-parts-of-mass.html|title=Thundersnow, hail and lightning reported during ice storm; thunderstorm warning issued for parts of Mass.|date=30 December 2019|access-date=5 December 2020|archive-date=31 December 2019|archive-url=https://web.archive.org/web/20191231005039/https://www.masslive.com/weather/2019/12/thundersnow-hail-and-lightning-reported-during-ice-storm-thunderstorm-warning-issued-in-parts-of-mass.html|url-status=live}}</ref> A "really rare" thundersnow storm occurred near [[Vancouver]], [[British Columbia]] on December 17–18, 2022.<ref>{{Cite web |title=Vancouver sky lit up by really rare 'thunder snow' |first=Irish Mae |last=Silvestre |url=https://dailyhive.com/vancouver/thunder-snow-vancouver |access-date=21 July 2023 |archive-url=https://web.archive.org/web/20230103085014/https://dailyhive.com/vancouver/thunder-snow-vancouver |archive-date=3 January 2023 |url-status=live |website=[[Daily Hive]] |language=en}}</ref>

The [[South Region, Brazil|South Region]] of [[Brazil]] registered episodes of thundersnow in 1984 and 2005, in the state of [[Santa Catarina (state)|Santa Catarina]], and in August 2011, in some municipalities of the highland region of [[Serra Gaúcha]], in the southern state of [[Rio Grande do Sul]].<ref>{{Cite web|title=Estado registra episódio inédito de neve com trovoadas (Rio Grande do Sul registered an unprecedented episode of thundersnow)|url=https://www.correiodopovo.com.br/notícias/geral/estado-registra-episódio-inédito-de-neve-com-trovoadas-1.68858|publisher=[[Correio do Povo]]|date=4 August 2011|access-date=16 August 2019|language=pt-br|archive-date=16 August 2019|archive-url=https://web.archive.org/web/20190816180507/https://www.correiodopovo.com.br/not%C3%ADcias/geral/estado-registra-epis%C3%B3dio-in%C3%A9dito-de-neve-com-trovoadas-1.68858|url-status=live}}</ref>

===Europe===
The [[British Isles]] and other parts of northwestern Europe occasionally report thunder and lightning during sleet or (usually wet) snow showers during winter and spring. [[Scotland]] registered an episode of thundersnow in the early hours of 4 December 2020, the unusual noise causing alarm among local people.<ref>{{Cite news|date=4 December 2020|title=Disruption after 'thundersnow' hits Scotland|language=en-GB|work=BBC News|url=https://www.bbc.com/news/uk-scotland-edinburgh-east-fife-55184493|access-date=4 December 2020|archive-date=4 December 2020|archive-url=https://web.archive.org/web/20201204082227/https://www.bbc.com/news/uk-scotland-edinburgh-east-fife-55184493|url-status=live}}</ref> The [[Met Office]] warned of thundersnow in Scotland, [[Wales]] and [[northern England]] in early January 2022.<ref>{{cite web |author1=Rachel Hall |date=5 January 2022 |title=UK weather: 'thundersnow' to fall from Thursday, warns Met Office |url=https://www.theguardian.com/uk-news/2022/jan/05/uk-weather-thundersnow-to-fall-from-thursday-warns-met-office |url-status=live |archive-url=https://web.archive.org/web/20220111174230/https://www.theguardian.com/uk-news/2022/jan/05/uk-weather-thundersnow-to-fall-from-thursday-warns-met-office |archive-date=11 January 2022 |access-date=11 January 2022 |website=[[The Guardian]]}}</ref>

Western Europe has rare occurrences of thundersnow, as on 8 March 2010, when northeastern [[Catalonia]], including [[Barcelona]], experienced a heavy snowfall accompanied by lightning, with snow depths surpassing {{convert|30|cm|in}} in low altitude areas.<ref>{{citation |title=Remote sensing analysis of a Mediterranean thundersnow and low-altitude heavy snowfall event |date=1 April 2013 |url=https://www.researchgate.net/publication/231401284 |periodical=Atmospheric Research |issue=123 |pages=305–322 |author1-last=Bech |author1-first=Joan |author2-last=Pineda |author2-first=Nicolau |author3-last=Rigo |author3-first=Tomeu |author4-last=Aran |author4-first=Montserrat|volume=123 |doi=10.1016/j.atmosres.2012.06.021 |bibcode=2013AtmRe.123..305B }}</ref>

In Central Europe, a large-area (non-local) thundersnow occurred on 17 January 2022, when a strong synoptic-scale squall line passed north to south over whole central and eastern Poland, precipitating both granular snow and snowflakes, with discharge intensity exceeding 100 per minute.<ref>{{cite web |date=17 January 2022 |title=Strong squall line across Poland, winds up to 120 km/h |url=https://fanipogody.pl/piekielnie-silna-linia-szkwalu-w-polsce-wichura-120-km-h-atak-zimy-i-paraliz-komunikacyjny/ |url-status=live |archive-url=https://web.archive.org/web/20220118182756/https://fanipogody.pl/piekielnie-silna-linia-szkwalu-w-polsce-wichura-120-km-h-atak-zimy-i-paraliz-komunikacyjny/ |archive-date=18 January 2022 |access-date=17 January 2022 |website=fanipogody.pl}}</ref> Other recent occurrences were in Poland and the Czech Republic in January 2023, [[Germany]] in January 2021, and [[Norway]] and [[Netherlands]] as well as [[Austria]] in April 2021, with previous occurrences in Norway in January 2019<ref>{{Cite web|url=https://www.adressa.no/nyheter/trondelag/2019/01/14/Et-lysshow-uten-side-stykke-i-sn%C3%B8drivet-18237949.ece|title=- Et lysshow uten side-stykke i snødrivet|date=14 January 2019|access-date=14 January 2022|language=nb|publisher=[[Adressa]]|url-access=subscription|archive-date=14 January 2022|archive-url=https://web.archive.org/web/20220114154740/https://www.adressa.no/nyheter/trondelag/2019/01/14/Et-lysshow-uten-side-stykke-i-sn%C3%B8drivet-18237949.ece|url-status=live |last1=Eggen |first1=Camilla Kilnes }}</ref> and January 2020.<ref>{{Cite web|url=https://www.adressa.no/pluss/nyheter/2020/01/09/Over-1000-lynnedslag-i-Midt-Norge-p%C3%A5-ett-d%C3%B8gn-Sjelden-det-er-s%C3%A5-mye-vintertorden-som-dette-20788273.ece|title=Over 1000 lynnedslag i Midt-Norge på ett døgn: - Sjelden det er så mye vintertorden som dette|date=9 January 2020|access-date=14 January 2022|publisher=[[Adressa]]|language=nb|url-access=subscription|archive-date=14 January 2022|archive-url=https://web.archive.org/web/20220114154731/https://www.adressa.no/pluss/nyheter/2020/01/09/Over-1000-lynnedslag-i-Midt-Norge-p%C3%A5-ett-d%C3%B8gn-Sjelden-det-er-s%C3%A5-mye-vintertorden-som-dette-20788273.ece|url-status=live |last1=Cadamarteri |first1=Frank }}</ref> [[Stockholm]] experienced thundersnow on 21 November 2022.<ref>{{Citation |title=Kraftiga smällar över Stockholm – mitt i ovädret - Aftonbladet TV |url=https://tv.aftonbladet.se/video/349362/kraftiga-smallar-over-stockholm-mitt-i-ovadret |language=sv |access-date=2022-11-21}}</ref><ref>{{Cite news |last1=Lundahl |first1=Marie |date=21 November 2022 |title=Snöblixtar över Stockholm – "Åsksnö" |language=sv |work=SVT Nyheter |url=https://www.svt.se/nyheter/lokalt/stockholm/snoblixtar-over-stockholm |access-date=21 November 2022}}</ref>

===Asia===
Low-pressure events in the eastern [[Mediterranean]] that originate from polar origin cause copious thundersnow occurrences during winter storms, especially over the elevated provinces of [[Israel]] and [[Jordan]], including [[Amman]] and [[Jerusalem]]. When such storms happen at areas intended for skiing, the mountains are often evacuated for safety.{{Citation needed|date=July 2023}}

Thundersnow is also common around [[Kanazawa, Ishikawa|Kanazawa]] and the [[Sea of Japan]], and even around [[Mount Everest]].{{Citation needed|date=July 2023}}

==Formation==
Thundersnow is caused by the same mechanisms as regular [[thunderstorm]]s, but it is much more rare because cold dense air is less likely to rise.<ref>{{Cite news |last=Strong |first=Hannah |date=Feb 25, 2022 |title=What is Thundersnow |work=[[WDRB]] |url=https://www.wdrb.com/weather/wdrb-weather-blog/what-is-thundersnow/article_965b3074-8f64-11ec-bb8d-d315410c9e0e.html |access-date=February 27, 2022 |archive-date=February 27, 2022 |archive-url=https://web.archive.org/web/20220227234256/https://www.wdrb.com/weather/wdrb-weather-blog/what-is-thundersnow/article_965b3074-8f64-11ec-bb8d-d315410c9e0e.html |url-status=live }}</ref>

===Lake effect precipitation===
[[Image:October_12-13_radarloop_kbuf.gif|thumb|right|A large squall producing heavy snow and frequent lightning over Buffalo, NY.]]
Lake effect thundersnow occurs after a cold front or [[Shortwave (meteorology)|shortwave]] aloft passes over a body of water. This steepens the thermal [[lapse rate]]s between the lake temperature and the temperatures aloft. A difference in temperature of {{convert|25|C-change}} or more between the lake temperature and the temperature at about {{convert|1500|m|ft|abbr=on}} (the 850 hPa level) usually marks the onset of thundersnow, if surface temperatures are expected to be below freezing. However several factors, including other geographical elements, affect the development of thundersnow.

The primary factor is convective depth. This is the vertical depth in the [[troposphere]] that a parcel of air will rise from the ground before it reaches the equilibrium (EQL) level and stops rising. A minimum depth of {{convert|1500|m|ft|abbr=on}} is necessary, and an average depth of {{convert|3000|m|ft|abbr=on}} or more is generally accepted as sufficient. [[Wind shear]] is also a significant factor. Linear snow squall bands produce more thundersnow than clustered bands; thus a directional wind shear with a change of less than 12° between the ground and {{convert|2000|m|ft|abbr=on}} in height must be in place. However, any change in direction greater than 12° through that layer will tear the snow squall apart. A bare minimum [[Fetch (geography)|fetch]] of {{convert|50|km/h|mph|abbr=on}} is required so that the air passing over the lake or ocean water will become sufficiently saturated with moisture and will acquire thermal energy from the water.

The last component is the echo top or storm top temperature. This must be at least {{convert|-30|C}}. It is generally accepted that at this temperature there is no longer any [[Supercooling|super cooled]] water vapour present in a cloud, but just ice crystals suspended in the air. This allows for the interaction of the ice cloud and graupel pellets within the storm to generate a charge, resulting in lightning and thunder.<ref>the USA Today. Jack Williams. [https://www.usatoday.com/weather/wlakeeff.htm Warm water helps create Great Lakes snowstorms.] {{Webarchive|url=https://web.archive.org/web/20120315102449/http://www.usatoday.com/weather/wlakeeff.htm |date=2012-03-15 }} Retrieved on 01-11-2006.</ref>

===Synoptic forcing===
Synoptic snow storms tend to be large and complex, with many possible factors affecting the development of thundersnow. The best location in a storm to find thundersnow is typically in its [[NorthWest]] [[Quadrant (plane geometry)|quadrant]] (in the [[Northern Hemisphere]], based on observations in the [[Midwestern United States]]), within what is known as the "comma head" of a mature [[extratropical cyclone]].<ref>Patrick S. Market, Angela M. Oravetz, David Gaede, Evan Bookbinder, Rebecca Ebert, and Christopher Melick. [http://ams.confex.com/ams/pdfpapers/72662.pdf Upper Air Constant Pressure Composites of Midwestern Thundersnow Events.] {{Webarchive|url=https://web.archive.org/web/20110609170131/http://ams.confex.com/ams/pdfpapers/72662.pdf |date=2011-06-09 }} Retrieved on 01-11-2006.</ref><ref name="Rauber2014">{{cite journal |title=Stability and Charging Characteristics of the Comma Head region of Continental Winter Cyclones |journal=J. Atmos. Sci. |last=Rauber |first=R.M. |pages=1559–1582 |volume=71 |issue=5 |year=2014 |doi=10.1175/JAS-D-13-0253.1 |bibcode= 2014JAtS...71.1559R|display-authors=etal|doi-access=free }}</ref> Thundersnow can also be located underneath the [[Occluded front|TROWAL]], a trough of warm air aloft which shows up in a [[surface weather analysis]] as an inverted trough extending backward into the cold sector from the main cyclone.<ref>National Weather Service Office, St. Louis, Missouri. [http://www.crh.noaa.gov/lsx/science/pdfppt/thun_prox_soundings.ppt Thundersnow Proximity Soundings.] Retrieved on 01-11-2006. {{webarchive|url=https://web.archive.org/web/20110523213153/http://www.crh.noaa.gov/lsx/science/pdfppt/thun_prox_soundings.ppt |date=2011-05-23 }}</ref> In extreme cases, thunderstorms along the cold front are transported towards the center of the low-pressure system and will have their precipitation change to snow or ice, once the cold front becomes a portion of the occluded front.<ref name="Rauber2014"/> The [[1991 Halloween blizzard]], [[Superstorm of 1993]], and [[White Juan]] are examples of such blizzards featuring thundersnow.

===Upslope flow===
Similar to the lake effect regime, thundersnow is usually witnessed in terrain in the cold sector of an [[extratropical cyclone]] when a shortwave aloft moves into the region. The shortwave will steepen the local lapse rates, allowing for a greater possibility of both heavy snow at elevations where it is near or below freezing, and occasionally thundersnow.<ref>National Weather Service Office, Sacramento, California. Alexander Tardy. [http://www.wrh.noaa.gov/wrh/02TAs/0213/index.html Western Region Technical Attachment No. 02-13: Thundersnow in the Sierra Nevada.] Retrieved on 01-11-2006. {{webarchive|url=https://web.archive.org/web/20061014210656/http://www.wrh.noaa.gov/wrh/02TAs/0213/index.html |date=2006-10-14 }}</ref>

==Hazards==
Thundersnow produces heavy snowfall rates in the range of {{convert|2 to 4|in|cm|0|order=flip|abbr=on}} per hour. Snowfall of this intensity may [[Whiteout (weather)|limit visibilities severely]], even during light wind conditions. However, thundersnow is often a part of a severe [[winter storm]] or [[blizzard]]. Winds of above [[tropical storm]] [[Beaufort scale|force]] are frequent with thundersnow. As a result, visibilities in thundersnow are frequently under 2/5th of a mile. Additionally, such wind creates extreme [[wind chill]]s and may result in [[frostbite]]. Finally, there is a greater likelihood that thundersnow lightning will have a [[Lightning#Positive lightning|positive polarity]], which is associated with a greater destructive potential than the more common negatively-charged lightning.<ref name="GHCC primer2">{{cite web|url=http://thunder.nsstc.nasa.gov/primer/primer2.html |title=A Lightning Primer – Characteristics of a Storm |author1=Christian, Hugh J. |author2=McCook, Melanie A. |name-list-style=amp |work=NASA |url-status=dead |archive-url=https://web.archive.org/web/20160305002214/http://thunder.nsstc.nasa.gov/primer/primer2.html |archive-date=2016-03-05 }}</ref> That said, lightning is far less frequent in a thundersnow storm than in a summertime storm, and is usually of the cloud-to-cloud variety, rather than a strike that travels to the ground.<ref name="cnn"/>

== See also ==
* [[Blizzard warning]]
* [[Severe thunderstorm warning]]
* [[Severe weather terminology (United States)]]

== References ==
{{Reflist|30em}}

== External links ==
* [http://www.theweatherprediction.com/habyhints/334/ What causes thundersnow?]
* [http://weather.missouri.edu/ROCS/ROCS.html Research on Convective Snow] from [[University of Missouri]]
* [http://news.bbc.co.uk/1/hi/uk/7864183.stm Thundersnow caught on live BBC TV broadcast] – 1st Feb 2009 – Kent, United Kingdom

[[Category:Snow or ice weather phenomena]]
[[Category:Storm]]
[[Category:Weather hazards]]
[[Category:Weather warnings and advisories]]