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A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental and subarctic climates, these storms are not necessarily restricted to the winter season, but may occur in the late autumn and early spring as well. A snowstorm with strong winds and other conditions meeting certain criteria is called a blizzard.
Winter storms are formed when moist air rises up into the atmosphere, creating low pressure near the ground and clouds up in the air. The air can also be pushed upwards by hills or large mountains. The upward motion is called lift. [1] The moisture is collected by the wind from large bodies of water, such as a big lake or the ocean. If temperature is below freezing, 0 °C (32 °F), near the ground and up in the clouds, precipitation will fall as snow, ice, rain and snow mixed (sleet), ice pellets or even graupel (soft hail). [1] [2] Since cold air can not hold as much moisture as warm air, the total precipitation will be less than at higher temperature. [3]
Winter storm warnings will be issued if:
Snowstorms with wind speed of more than 35 mph (16 m/s) and reduced visibility of less than 0.25 miles (400 m) for 3 hours or longer are called blizzards. [5] [4]
Severe winter weather conditions called "winter storms", can be local weather fulfilling the criteria for 24 hours, or large storm systems covering part of a continent for several days. With large, massive winter storms, weather in any part of the area covered by the extreme weather is usually called "storm"; even if meteorological criteria for winter storms are not met everywhere. [6] An example of this is the February 13–17, 2021 North American winter storm with snowfall and below freezing temperatures as far south as Texas and the Gulf of Mexico. [7] [6]
Snowstorms are storms where large quantities of snow fall. 2 in (5.1 cm) of snow is enough to create serious disruptions to traffic and school transport (because of the difficulty to drive and manoeuvre the school buses on slick roads). This is particularly true in places where snowfall is not typical but heavy accumulating snowfalls can occur. In places where snowfall is typical, such small snowfalls are rarely disruptive, because of effective snow and ice removal by municipalities, increased use of four-wheel drive and snow tires, and drivers being more used to winter conditions. Snowfalls in excess of 6 in (15 cm) are usually universally disruptive.
A large number of severe snowstorms, some of which were blizzards, occurred in the United States during 1888 and 1947 as well as the early and mid-1990s. The snowfall of 1947 exceeded 2 ft (61 cm) with drifts and snow piles from plowing that reached 12 ft (3.7 m) and for months as temperatures did not rise high enough to melt the snow. The 1993 "Superstorm" manifested as a blizzard in most of the affected areas.
Severe snowstorms could be quite dangerous: a 6 in (15 cm) snow depth will make some unplowed roads impassable, and it is possible for cars to get stuck in the snow. Snow depth exceeding 12 in (30 cm) especially in southern or generally warm climates will cave the roofs of some homes and cause loss of electricity. Standing dead trees can also be brought down by the weight of the snow, especially if it is wet. Even a few inches of dry snow can form drifts many feet high under windy conditions.
Accumulated snow can make driving motor vehicles very hazardous. Snow on roadways reduces friction between tires and the road surface, which in turn lowers the maneuverability of a vehicle considerably. As a result, average driving speeds on public roads and highways are reduced by up to 40% while heavy snow is falling. [8] Visibility is reduced by falling snow, and this is further exacerbated by strong winds which are commonly associated with winter storms producing heavy snowfall. In extreme cases, this may lead to prolonged whiteout conditions in which visibility is reduced to only a few feet due to falling or blowing snow. These hazards can manifest even after snowfall has ended when strong winds are present, as these winds will pick up and transport fallen snow back onto roadways and reduce visibility in the process. This can even result in blizzard conditions if winds are strong enough. [9] Heavy snowfall can immobilize a vehicle entirely, which may be deadly depending on how long it takes rescue crews to arrive. The clogging of a vehicle's tailpipe by snow may lead to carbon monoxide buildup inside the cabin. [10]
Depending on the temperature profile in the atmosphere, snow can be either wet or dry. Dry snow, being lighter, is transported by wind more easily and accumulates more efficiently. Wet snow is heavier due to the increased water content. Significant accumulations of heavy wet snow can cause roof damage. It also requires considerably more energy to move and this can create health problems while shoveling when combined with the harsh weather conditions. Numerous deaths as a result of heart attacks can be attributed to snow removal. [11] Accretion of wet snow to elevated surfaces occurs when snow is "sticky" enough which can cause extensive tree and power line damage in a manner similar to ice accretion during ice storms. Power can be lost for days during a major winter storm, and this usually means the loss of heating inside buildings. Other than the obvious risk of hypothermia due to cold exposure, another deadly element associated with snowstorms is carbon monoxide poisoning which can happen anytime combustion products from generators or heating appliances are not properly vented. Partially or fully melted snow on roadways can refreeze when temperatures fall, creating black ice.
Heavy showers of freezing rain are one of the most dangerous types of winter storm. They typically occur when a layer of warm air hovers over a region, but the ambient temperature a few meters above the ground is near or below 0 °C (32 °F), and the ground temperature is sub-freezing.
While a 10 cm (3.9 in) snowfall is somewhat manageable by the standards of the northern United States and Canada, a comparable 10 mm (0.39 in) precipitation of an ice storm can paralyze a region; driving becomes extremely hazardous, telephone and power lines are damaged, and crops may be ruined. [12]
Notable ice storms include an El Niño-related North American ice storm of 1998 that affected much of eastern Canada, including Montreal and Ottawa, as well as upstate New York and parts of upper New England. Three million people lost power, some for as long as six weeks. One-third of the trees in Montreal's Mount Royal park were damaged, as well as a large proportion of the sugar-producing maple trees. The amount of economic damage caused by the storm has been estimated at $3 billion CAD.
In countries where winter storms can occur, governments and health organizations have websites and online services with advice about how to prepare for the consequences of severe weather. Advices vary with housing standards, infrastructure and safety regulations, but some tips are the same, such as: stock up on three days of food, water, medicines and hygiene items, keep warm clothes ready, keep a flashlight and extra batteries, stay informed, help each other, do not travel unless absolutely necessary. [16] [17] [18] [19]
A blizzard is a severe snowstorm characterized by strong sustained winds and low visibility, lasting for a prolonged period of time—typically at least three or four hours. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Blizzards can have an immense size and usually stretch to hundreds or thousands of kilometres.
Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water. The lower layer of air, heated by the lake water, picks up water vapor from the lake and rises through colder air. The vapor then freezes and is deposited on the leeward (downwind) shores.
A winter storm warning is a hazardous weather statement issued by Weather Forecast Offices (WFO) of the National Weather Service (NWS) in the United States to alert the public that a winter storm is occurring or is about to occur in the area, usually within 36 hours of the storm's onset.
This article describes severe weather terminology used by the National Weather Service (NWS) in the United States. The NWS, a government agency operating as an arm of the National Oceanic and Atmospheric Administration (NOAA) branch of the United States Department of Commerce (DoC), defines precise meanings for nearly all of its weather terms.
The Northeast Snowfall Impact Scale (NESIS) was created to measure snowstorms in the U.S. Northeast in much the same way the Saffir-Simpson Hurricane Scale records hurricane intensity and the Enhanced Fujita Scale with tornadoes.
The Early Winter 2006 North American storm complex was a severe winter storm that occurred on November 26, 2006, and continued into December 1. It affected much of North America in some form, producing various kinds of severe weather including a major ice storm, blizzard conditions, high winds, extreme cold, a serial derecho and some tornadoes.
Global storm activity of 2008 profiles the major worldwide storms, including blizzards, ice storms, and other winter events, from January 1, 2008 to December 31, 2008. A winter storm is an event in which the dominant varieties of precipitation are forms that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice to form. It may be marked by strong wind, thunder and lightning, heavy precipitation, such as ice, or wind transporting some substance through the atmosphere. Major dust storms, Hurricanes, cyclones, tornados, gales, flooding and rainstorms are also caused by such phenomena to a lesser or greater existent.
The December 1969 nor'easter was a strong winter storm that mainly affected the Northeastern United States and southern Quebec between December 25 and December 28, 1969. The multi-faceted storm system included a tornado outbreak, record snow accumulations, a damaging ice storm, and flooding rains.
The 2011 Groundhog Day blizzard was a powerful and historic winter storm that affected large swaths of the United States and Canada from January 31 to February 2, 2011, especially on Groundhog Day. During the initial stages of the storm, some meteorologists predicted that the system would affect over 100 million people in the United States. The storm brought cold air, heavy snowfall, blowing snow, and mixed precipitation on a path from New Mexico and northern Texas to New England and Eastern Canada. The Chicago area saw 21.2 inches (54 cm) of snow and blizzard conditions, with winds of over 60 mph (100 km/h). With such continuous winds, the blizzard continued to the north and affected Eastern and Atlantic Canada. Blizzard conditions affected many other large cities along the storm's path, including Tulsa, Oklahoma City, Kansas City, St. Louis, Springfield, El Paso, Las Cruces, Des Moines, Milwaukee, Detroit, Indianapolis, Dayton, Cleveland, New York City, New York's Capital District, and Boston. Many other areas not normally used to extreme winter conditions, including Albuquerque, Dallas and Houston, experienced significant snowfall or ice accumulation. The central Illinois National Weather Service in Lincoln, Illinois, issued only their fourth blizzard warning in the forecast office's 16-year history. Snowfall amounts of 20 to 28 inches were forecast for much of Northern and Western Illinois.
The 2015–16 North American winter was not as frigid across North America and the United States as compared to the 2013–14 and 2014–15 winters. This was mainly due to a strong El Niño, which caused generally warmer-than-average conditions. However, despite the warmth, significant weather systems still occurred, including a snowstorm and flash flooding in Texas at the end of December and a large tornado outbreak at the end of February. The main event of the winter season, by far and large, was when a crippling and historic blizzard struck the Northeastern United States in late January, dumping up to 3 feet of snow in and around the metropolitan areas. Several other smaller snow events affected the Northeast as well, but for the most part the heaviest snowstorms and ice stayed out further west, such as a severe blizzard in western Texas in late December, and a major late-season snowstorm in Colorado in mid-April.
The 2011–12 North American winter by and large saw above normal average temperatures across North America, with the Contiguous United States encountering its fourth-warmest winter on record, along with an unusually low number of significant winter precipitation events. The primary outlier was Alaska, parts of which experienced their coldest January on record.
The 2010–11 North American winter was influenced by an ongoing La Niña, seeing winter storms and very cold temperatures affect a large portion of the Continental United States, even as far south as the Texas Panhandle. Notable events included a major blizzard that struck the Northeastern United States in late December with up to 2 feet (24 in) of snowfall and a significant tornado outbreak on New Year's Eve in the Southern United States. By far the most notable event was a historic blizzard that impacted areas from Oklahoma to Michigan in early February. The blizzard broke numerous snowfall records, and was one of the few winter storms to rank as a Category 5 on the Regional Snowfall Index. In addition, Oklahoma set a statewide low temperature record in February.
The 2016–17 North American winter was quite warm across North America in general, due in part to a weak La Niña that was expected to influence weather conditions across the continent. Several notable events occurred during the season, including a potent winter storm that affected the East Coast of the United States in early January, the second-largest winter tornado outbreak on record later that month, and an unusually warm February. In addition, towards the end of the season, a large cyclonic storm system that caused a large tornado outbreak, flooding, and a potent blizzard occurred in the Heartland of the country. However, the most notable event of the winter was a powerful blizzard that impacted the Northeast and New England in mid-March, towards the end of the season.
The 2017–18 North American winter saw weather patterns across North America that were very active, erratic, and protracted, especially near the end of the season, resulting in widespread snow and cold across the continent during the winter. Significant events included rare snowfall in the South, an outbreak of frigid temperatures that affected the United States during the final week of 2017 and early weeks of January, and a series of strong nor'easters that affected the Northeastern United States during the month of March. In addition, flooding also took place during the month of February in the Central United States. Finally the winter came to a conclusion with a powerful storm system that caused a tornado outbreak and blizzard in mid-April. The most intense event, however, was an extremely powerful cyclonic blizzard that impacted the Northeastern United States in the first week of 2018. Similar to the previous winter, a La Niña was expected to influence the winter weather across North America.
The 2018–19 North American winter was unusually cold within the Northern United States, with frigid temperatures being recorded within the middle of the season. Several notable events occurred, such as a rare snow in the Southeast in December, a strong cold wave and several major winter storms in the Midwest, and upper Northeast and much of Canada in late January and early February, record snowstorms in the Southwest in late February, deadly tornado outbreaks in the Southeast and a historic mid-April blizzard in the Midwest, but the most notable event of the winter was a record-breaking bomb cyclone that affected much of the Central United States and Canada in mid-March. Unlike previous winters, a developing weak El Niño was expected to influence weather patterns across North America. Overall, however, winter of 2018–19 was mild along the mid- and lower parts of the East Coast, the West Coast, and most of the southern Plains. Overall, the meteorological winter of 2018-19 became the wettest on record for the United States.
The 2019–20 North American winter was unusually warm for many parts of the United States; in many areas, neutral ENSO conditions controlled the weather patterns, resulting in the sixth-warmest winter on record, and many areas in the Northeastern United States saw one of the least snowy winters in years. In fact, Baltimore and Islip saw no snow in February for the first time. Some notable events still occurred, such as a powerful blizzard that impacted the Western United States in late November, a series of cold shots in January and February, a snowstorm within the Texas Panhandle and a late-season blizzard in the High Plains.
The 2020–21 North American winter was the most significant winter season to affect North America in several years, and the costliest on record, with a damage total of at least $33.35 billion. The season featured 6 storms ranking on the Regional Snowfall Index scale, with 4 storms ranking as at least a Category 3. Most of the winter's damage and fatalities occurred due to a historic and major cold wave in mid-February. Several other significant events occurred, including a crippling early-season ice storm in the Southern Plains, a powerful nor'easter in mid-December, another major nor'easter in early February, two major and widespread winter storms in mid-February, and a major blizzard in the Rocky Mountains in mid-March. The winter-related events were responsible for at least 358 fatalities, making it the deadliest season since 1992–93. A La Niña pattern influenced much of the winter in North America.
The 2021–22 North American winter was not as significant and record-breaking as the previous winter season. Despite this, several notable and significant events still occurred, including two separate record-breaking tornado outbreaks in mid-December, a significant winter storm in the South in mid-January, a powerful blizzard that impacted the Northeast coast at the end of January and a wide-ranging, significant winter storm that affected most of the eastern half of the country in early February. Additional significant events included a late-season winter storm in March that affected the Appalachian Mountains, and a major blizzard that affected North and South Dakota in mid-April. Additionally, a very late out-of-season snowstorm struck the Rocky Mountains in late May. During the season, four storms have been ranked on the Regional Snowfall Index (RSI), although none attained the “Major” category. Similar to the previous winter, a developing La Niña was expected to influence weather patterns across the continent.
The January 2022 North American blizzard caused widespread and disruptive impacts to the Atlantic coast of North America from Delaware to Nova Scotia with as much as 2.5 feet (30 in) of snowfall, blizzard conditions and coastal flooding at the end of January 2022. Forming from the energy of a strong mid- to upper-level trough, the system developed into a low-pressure area off the Southeast United States on January 28. The system then quickly intensified that night as it traveled northeast parallel to the coast on January 29, bringing heavy snowfall blown by high winds to the East Coast of the continent. Further north, it also moved inland in Maine and its width meant it strongly impacted all three of Canada's Maritime provinces. In some areas, mainly the coastal regions of New Jersey, Long Island and Massachusetts, it was the first blizzard since a storm in January 2018. The storm was considered a "bomb cyclone" as it rapidly intensified and barometric pressure dropped at least 24 millibars over a 24-hour period. The storm was given names such as Blizzard of 2022 and Winter Storm Kenan.
The 2022–23 North American winter was an unusually warm winter for the east and an unusually cold winter for the west in North America, as it occurred across the continent from late 2022 to early 2023. The winter season in North America began at the winter solstice, which occurred on December 21, 2022, and it ended at the March equinox, which occurred on March 20, 2023. The first day of meteorological winter began on December 1 and unofficially ended on February 28; winter storms may still occur outside of these limits.
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