}}
The '''2010–11 North American winter''' was influenced by an ongoing [[2010–12 La Niña event|La Niña]], seeing winter storms and very cold temperatures affect a large portion of the continental [[Continental United States]], even as far south as the [[Texas Panhandle]]. Notable events included [[December 2010 North American blizzard|a major blizzard]] that struck the [[Northeastern United States]] in late December with up to {{convert|2|ft|in}} of snowfall and a [[2010 New Year's Eve tornado outbreak|significant tornado outbreak]] on New Year's Eve in the southern[[Southern United States]]. By far the most notable event was [[January 31 – February 2, 2011 North American blizzard|a historic blizzard]] that impacted areas from [[Oklahoma]] to [[Michigan]] in early February. whichThe blizzard broke numerous snowfall records, and was one of the few winter storms to rank as a [[List of Regional Snowfall Index Category 5 winter storms|Category 5]] on the [[Regional Snowfall Index]]. In addition, [[Oklahoma]] set a statewide low temperature record in February.<ref>{{Cite web|url=https://www.poncacitynews.com/news/oklahoma-winter-weather-look-records-broken-so-far|title=Oklahoma winter weather: A look at the records broken so far | Ponca City News}}</ref>
While there is no well-agreed-upon date used to indicate the start of winter in the [[Northern Hemisphere]], there are two definitions of winter which may be used. Based on the astronomical definition, winter begins at the [[winter solstice]], which in 2010 occurred late on December 21 (early on December 22 in [[Eastern Time Zone|EST]]), and ends at the [[March equinox]], which in 2011 occurred on March 20.<ref name="USNO Seasons">{{cite web|title=Earth's Seasons: Equinoxes, Solstices, Perihelion, and Aphelion |url=http://aa.usno.navy.mil/data/docs/EarthSeasons.php |publisher=[[United States Naval Observatory]] |date=September 21, 2015 |access-date=June 14, 2016 |location=[[Washington, D.C.]] |format=PHP |archive-url=https://web.archive.org/web/20150831000837/http://aa.usno.navy.mil/data/docs/EarthSeasons.php |archive-date=August 31, 2015 |url-status=live }}</ref> Based on the meteorological definition, the first day of winter is December 1 and the last day February 28.<ref name="NOAA/NWS-Seasons">{{cite web|title=Meteorological vs. Astronomical Seasons|url=https://www.ncdc.noaa.gov/news/meteorological-versus-astronomical-summer%E2%80%94what%E2%80%99s-difference|publisher=NOAA National Centers for Environmental Information|date=June 21, 2013|access-date=June 14, 2016}}</ref> Both definitions involve a period of approximately three months, with some variability.
== Seasonal forecasts ==
=== Late October bomb cyclone ===
{{main|October 2010 North American storm complex}}
In late October, a massive cyclone brought a serial [[derecho]] to a large portion of the United States, as well an early season blizzard to parts of the [[Midwest]] and [[Canadian Prairies]] from October 25 through October 28. Forming over the Upper Midwest, it intensified rapidly prompting the storm to be classified as a [[Explosive cyclogenesis|bomb cyclone]] which are more common over the ocean rather than over land.<ref>{{cite web|title=Strong Extratropical Cyclone over the US Midwest|url=https://earthobservatory.nasa.gov/IOTD/view.php?id=46662|website=Earth Observatory| date=29 October 2010 |publisher=NASA|access-date=30 April 2017}}</ref> The massive storm across the entire country and up into [[Canada]] bringing a wide variety of weather. It was responsible for 69 tornadoes across the country with an EF2 being the highest category. It had its highest recorded winds in Nebraska at {{convert|70 |mph (112.6 |km/h)|abbr=on}} and the highest recorded snowfall totals being {{convert|9 |in ( 22.9 |cm)|abbr=on}} in [[St. Louis County, Minnesota]].<ref>{{cite web|last1=Gerhardt|first1=Mary Beth|title=Midwest High Wind Event|url=http://www.wpc.ncep.noaa.gov/winter_storm_summaries/event_reviews/2010/Midwest_High_Wind2010.pdf|website=wpc.ncep.noaa.gov|publisher=NWS|access-date=2 May 2017}}</ref>
=== Late December blizzard ===
[[File:Atmospheric River GOES WV 20101220.1200.goes11.vapor.x.pacus.x.jpg|thumb]]
{{main|December 2010 North American blizzard}}
This was a long-lived storm that primarily effected the Pacific Northwest and eastern regions of the US and Canada. The storm developed along the so-called Pineapple Express [[Atmospheric river]] as a disturbance in the [[Gulf of Alaska]] on December 5 and intensified as it began to move toward land. By the 8th it reached the coast of northwest North America but significantly weakened and a new storm formed in the Gulf of Alaska. By December 15 the storm had moved back toward the west coast and interacted with a [[kona low]] situated over Hawaii which feed the storm more energy through the Pineapple Express. The storm had undergone [[Explosive cyclogenesis]] on December 19, which caused flooding and mudslides in California.<ref>{{cite web|title=Pineapple Express blamed for S. Cal storms|url=http://www.upi.com/Top_News/US/2010/12/22/S-Calif-storm-unleashes-torrent-of-rain/UPI-41611293008400/|website=UPI|publisher=UPI|access-date=28 April 2017}}</ref> It would start to weaken as it move towards the [[Gulf of Mexico]]. It would dump snow on the mountains of Southern California and the 4 Corners region of the Country. When the storm reached Texas it absorbed [[Gulf Stream]] moisture and reintensified as it moved toward the Florida Panhandle on December 24. It transferred into a nor'easter as it moved up the east coast on December 27. It dumped snow on a portion of the Mid Atlantic and New England and was officially classified as a blizzard in New York City.<ref>{{cite web|title=The Blizzard of 25-27 December 2010: Forecast Analysis|url=http://www.wpc.ncep.noaa.gov/winter_storm_summaries/event_reviews/2010/December25_27_2010_Blizzard.pdf|website=wpc.ncep.noaa.gov|access-date=29 April 2017}}</ref> North Carolina saw snowfall totals as high as {{convert|12 inches (30 |in|cm)}}. Philadelphia received {{convert|12.2 inches (31 |in|cm)}} of snow and nearby Trenton, New Jersey saw upwards of {{convert|20 |in (51 |cm)|abbr=on}} snowfall totals. New York City and surrounding cities received anywhere from {{convert|12 inches (30 |in|cm)}} to {{convert|32 inches (81 |in|cm)}} of snow. Boston and coastal areas of Virginia saw only {{convert|12 inches (30 |in|cm)}} of snow. Wind gusts reached {{convert|40–50 miles per hour (64-80 kp|mph|km/h)|abbr=out}} in certain areas, creating horrible driving conditions.<ref>{{cite web|title=The Weather Prediction Center Storm Summary Message|url=http://www.wpc.ncep.noaa.gov/discussions/nfdscc1.html|website=wpc.ncep.noaa.gov|publisher=NWS|access-date=29 April 2017}}</ref> The highest winds were recorded in Nova Scotia of 94.4 MPH (151.9 kp/h).
=== New Year's Eve tornado outbreak ===
[[File:2010 New Year's Eve tornado outbreak map.png|thumb|A map of the tornadoes that struck.]]
{{main|2010 New Year's Eve tornado outbreak}}
A tornado outbreak struck the southern United States in late December. The [[Storm Prediction Center]] has been calling for a significant severe weather event since December 25. However the predictability of the event was uncertain but, forecasts gained confidence as the event drew closer. On December 30 only marginally conductive conditions were present for a severe weather to form. Later on an approaching cold front induced supercells to form in the evening hours. The storm had spawned up to 5 EF3 tornadoes. The highest recorded non tornadic winds were {{convert|80 |mph (130 |km/h)|abbr=on}}. On December 30, a few tornadoes were reported in portions of [[Arkansas]]. On the morning of December 31 there were several reports of tornadoes in [[Illinois]] and [[Missouri]]. In the afternoon and into the next day in [[Mississippi]], a tornado in [[Jackson, Mississippi]], prompted a [[tornado emergency]] to be issued.<ref>{{cite web|title=Storm Prediction Center 20101231's storm reports|url=http://www.spc.noaa.gov/climo/reports/101231_rpts.html|website=spc.noaa.gov|publisher=NWS|access-date=2 May 2017}}</ref><ref>{{cite web|url=https://www.ncdc.noaa.gov/stormevents/listevents.jsp?eventType=%28C%29+Flash+Flood&eventType=%28Z%29+Flood&eventType=%28C%29+Hail&eventType=%28C%29+Heavy+Rain&eventType=%28C%29+Thunderstorm+Wind&eventType=%28C%29+Tornado&beginDate_mm=12&beginDate_dd=30&beginDate_yyyy=2010&endDate_mm=01&endDate_dd=02&endDate_yyyy=2011&hailfilter=0.00&tornfilter=0&windfilter=000&sort=DT&submitbutton=Search&statefips=-999%2CALL# |title=Storm Events Database |website=ncdc.noaa.gov|publisher=NWS|access-date=2 May 2017}}</ref>
=== Early January blizzard ===
{{main|January 8–13, 2011 North American blizzard}}
{{Unsourced section|date=July 2023}}
In the middle of January, a storm formed in the Gulf of Mexico and interacted with cold air mass in Canada. This storm would eventually merge with an [[Alberta clipper]] over [[Cape Hatteras]]. It would track up the east coast as a nor'easter before moving out to sea. It would bring winter weathering the form of snow and freezing rain from Texas to Atlantic Canada. It brought snowfall to areas that got hit hard by the previous blizzard. In New England there were reports of 2 feet of snow.
=== Late January blizzard ===
{{main|January 25–27, 2011 North American blizzard}}
In late January, another major snowstorm hit the Northeast. It brought a winter storm to the mid Atlantic and a blizzard to New England. It hit two weeks after the previous nor'easter and one month after the December nor'easter, striking one week before the historic blizzard. The first part of this system hit the northeast as a coastal low with snow lasting from early January 26 to mid day of January 27. The second round of snow came when an upper -level low moved from eastern [[Tennessee]] to southern New England. This round had much steeper lapse rates than the first round and there were reports of [[thundersnow]] in some of the heavier bands. Areas with rain had gradually changed over to freezing rain then sleet.<ref>{{cite web|last1=Hamrick|first1=Dave|title=Mid-Atlantic and Northeast U.S. Winter Storm January 26-27, 2011|url=http://www.wpc.ncep.noaa.gov/winter_storm_summaries/event_reviews/2011/Mid-Atlantic_Northeast_WinterStorm_Jan2011.pdf|website=wpc.ncep.noaa.gov|publisher=NWS|access-date=3 April 2017}}</ref>
=== Groundhog Day blizzard ===
[[File:Late January 2011 winter storm blanketing the US, on January 31, 2011.jpg|thumb|Satellite image of the storm developing on January 31st]]
{{main|2011 Groundhog Day blizzard}}
On January 31, a low-pressure system formed in [[Montana]], and merged with a storm that pushed in from Northern California and a third storm in the Gulf of Mexico over the Midwest, on February 1, and rapidly intensified. The resulting storm brought a historic blizzard to the Midwest. It was the first storm to rank as a [[List of Regional Snowfall Index Category 5 winter storms|Category 5 on the RSI]] since 2009. It brought a tornado outbreak to the southeast states with most reported in Alabama. It brought a blizzard and winter storm from New Mexico to New England and later up into Atlantic Canada. Chicago received 1 to 2 feet of snow and 60 mph winds.<ref>{{cite web|title=NWS Chicago|url=http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=lot&storyid=63527&source=2#snowfall_totals|publisher=NWS|access-date=28 March 2017}}</ref> The greater area of northern [[Illinois]] getting anywhere from 20 to 28 inches of snow. It hit the Midwest and New England with an ice storm along the warm front and mixed precipitation from New Mexico to Northern Texas. This ice storm brought {{convert|1 inch (2.5 |in|cm)}} of ice to several areas.<ref>{{cite web|last1=Pazniokas|first1=Mark|title=Malloy: Ice storm could be more trouble than record snows|date=February 2011 |url=https://ctmirror.org/2011/02/01/malloy-ice-storm-could-be-more-trouble-record-snows/|publisher=ct mirror|access-date=28 March 2017}}</ref>
=== Mid-April storm complex ===
{{DEFAULTSORT:2010-11 North American winter}}
[[Category:2010 in Canada|Winter]]
[[Category:2011 in Canada|Winter]]
[[Category:2010 in the United States|Winter]]
[[Category:2011 in the United States|Winter]]
[[Category:20102010–11 North American winter| meteorology]]
[[Category:2011 meteorology]]
[[Category:North American winters]]
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