Surface weather analysis is a special type of weather map that provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations.
The North American Ice Storm of 1998 was a massive combination of five smaller successive ice storms in January 1998 that struck a relatively narrow swath of land from eastern Ontario to southern Quebec, New Brunswick and Nova Scotia in Canada, and bordering areas from northern New York to central Maine in the United States. It caused massive damage to trees and electrical infrastructure throughout the area, leading to widespread long-term power outages. Millions were left in the dark for periods varying from days to several weeks, and in some instances, months. It led to 34 fatalities, a shutdown of activities in large cities like Montreal and Ottawa, and an unprecedented effort in reconstruction of the power grid. The ice storm led to the largest deployment of Canadian military personnel since the Korean War, with over 16,000 Canadian Forces personnel deployed, 12,000 in Quebec and 4,000 in Ontario at the height of the crisis.
The tornado outbreak sequence of March 1913 was a devastating series of tornado outbreaks that affected the northern Great Plains, the Southern United States, and sections of the upper Midwest over a two-day-long period between March 21–23, 1913. Composed of two outbreaks, the sequence first began with a tornado outbreak that commenced in Mississippi early on March 21. Several significant tornadoes occurred, one of which killed seven people in one family and another destroyed much of Lower Peach Tree, Alabama, with 27 deaths all in that town. The tornado at Lower Peach Tree is estimated to have been equivalent to a violent F4 tornado on the Fujita scale, based upon damage accounts. The tornadoes occurred between 0630 and 1030 UTC, or pre-dawn local time, perhaps accounting for the high number of fatalities—a common trend in tornadoes in the Dixie Alley. In all, tornadoes in Mississippi, Georgia, and Alabama killed 48 people, perhaps more, that day and injured at least 150 people.
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.
The January 2007 North American ice storm was a severe ice storm that affected a large swath of North America from the Rio Grande Valley to New England and southeastern Canada, starting on January 11 and lasting until January 16. It was followed by a second wave in the Southern United States from Texas to the Carolinas from January 16 through January 18, and a third one that hit the southern Plains and mid-Atlantic states as well as Newfoundland and Labrador from January 19 to January 24. It resulted in at least 74 deaths across 12 U.S. states and three Canadian provinces, and caused hundreds of thousands of residents across the U.S. and Canada to lose electric power.
The February 2007 North American blizzard was a massive winter storm that affected most of the eastern half of North America, starting on February 12, 2007 and peaking on Valentine's Day, February 14. The storm produced heavy snowfalls across the midwestern United States from Nebraska to Ohio and produced similar conditions across parts of the northeastern United States, and into Canada in Ontario, Quebec and New Brunswick. Significant sleet and freezing rain fell across the southern Ohio Valley and affected portions of the east coast of the United States, including the cities of Boston, Baltimore, Washington, D.C., New York City and Philadelphia.
The Mid-December 2007 North American winter storms were a series of two winter storms that affected much of central and eastern North America, from December 8 to December 18, 2007. The systems affected areas from Oklahoma to Newfoundland and Labrador with freezing rain, thunderstorms, sleet, snow, damaging winds, and blizzard-like conditions in various areas. The first two storms produced copious amounts of ice across the Midwestern United States and Great Plains from December 8 to December 11, knocking out power to approximately 1.5 million customers from Oklahoma north to Iowa. The second storm moved northeast, producing heavy snow across New York and New England. A third storm was responsible for a major winter storm from Kansas to the Canadian Maritimes, bringing locally record-breaking snowfalls to Ontario, an icestorm across the Appalachians, and thunderstorms and 9 tornadoes to the Southeastern United States.
The climate of the United States varies due to changes in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.
The tornado outbreak sequence of June 3–11, 2008 was a series of tornado outbreaks affecting most of central and eastern North America from June 3–11, 2008. 192 tornadoes were confirmed, along with widespread straight–line wind wind damage. Seven people were killed from a direct result of tornadoes; four in Iowa, two in Kansas, and one in Indiana. Eleven additional people were killed across five states by other weather events including lightning, flash flooding, and straight-line winds. Severe flooding was also reported in much of Indiana, Wisconsin, Minnesota and Iowa as a result of the same thunderstorms, while high heat and humidity affected much of eastern North America; particularly along the eastern seaboard of the United States from New York City to the Carolinas.
A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone, at the leading edge of its cold air advection pattern—known as the cyclone's dry "conveyor belt" flow. Temperature differences across the boundary can exceed 30 °C (54 °F) from one side to the other. When enough moisture is present, rain can occur along the boundary. If there is significant instability along the boundary, a narrow line of thunderstorms can form along the frontal zone. If instability is weak, a broad shield of rain can move in behind the front, and evaporative cooling of the rain can increase the temperature difference across the front. Cold fronts are stronger in the fall and spring transition seasons and are weakest during the summer.
From May 3 to May 11, 2003, a prolonged and destructive series of tornado outbreaks affected much of the Great Plains and Eastern United States. Most of the severe activity was concentrated between May 4 and May 10, which saw more tornadoes than any other week-long span in recorded history; 335 tornadoes occurred during this period, concentrated in the Ozarks and central Mississippi River Valley. Additional tornadoes were produced by the same storm systems from May 3 to May 11, producing 363 tornadoes overall, of which 62 were significant. Six of the tornadoes were rated F4, and of these four occurred on May 4, the most prolific day of the tornado outbreak sequence; these were the outbreak's strongest tornadoes. Damage caused by the severe weather and associated flooding amounted to US$4.1 billion, making it the costliest U.S. tornado outbreak of the 2000s. A total of 50 deaths and 713 injuries were caused by the severe weather, with a majority caused by tornadoes; the deadliest tornado was an F4 that struck Madison and Henderson counties in Tennessee, killing 11. In 2023, tornado expert Thomas P. Grazulis created the outbreak intensity score (OIS) as a way to rank various tornado outbreaks. The tornado outbreak sequence of May 2003 received an OIS of 232, making it the fourth worst tornado outbreak in recorded history.
From May 10–13, 2010, a major tornado outbreak affected large areas of Oklahoma, Kansas, Missouri, and Arkansas, with the bulk of the activity in central and eastern Oklahoma. Over 60 tornadoes, some large and multiple-vortex in nature, affected large parts of Oklahoma and adjacent parts of southern Kansas and Missouri, with the most destructive tornadoes causing severe damage in southern suburbs of the Oklahoma City metropolitan area and just east of Norman, Oklahoma, where the fatalities were reported from both tornado tracks. The outbreak was responsible for three fatalities, all of which occurred in Oklahoma. Damage was estimated to be over $595 million in central Oklahoma alone.
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.
Global weather activity of 2007 profiles the major worldwide weather events, including blizzards, ice storms, tornadoes, tropical cyclones, and other weather events, from January 1, 2007, to December 31, 2007. Winter storms are events in which the dominant varieties of precipitation are formed during cold temperatures; they include snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice, including freezing rain, to form. Thehy may be marked by strong wind, thunder, lightning thunderstorms, heavy precipitation, including ice storm, wind transporting some substance through the atmosphere, including dust storms, snowstorms, and hail storms. Other major non winter events such as large dust storms, hurricanes, cyclones, tornados, gales, flooding, and rainstorms are also caused by such phenomena.
The 2013–14 North American winter was one of the most significant for the United States, due in part to the breakdown of the polar vortex in November 2013, which allowed very cold air to travel down into the United States, leading to an extended period of very cold temperatures. The pattern continued mostly uninterrupted throughout the winter and numerous significant winter storms affected the Eastern United States, with the most notable one being a powerful winter storm that dumped ice and snow in the Southeastern United States and the Northeastern United States in mid-February. Most of the cold weather abated by the end of March, though a few winter storms did affect the Western United States towards the end of the winter.
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 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 January 4–8, 2017 North American winter storm was a major snow and ice storm that affected the Lower 48 of the United States with winter weather. Moving ashore on the West Coast on January 3, the system produced heavy snowfall in the Sierra Mountains, with nearly 4 feet of snowfall falling in the highest elevations. After impacting the Northwest and Southwest, the winter storm went on to strike the Southeast on January 5–6 with snow and ice, with snowfall accumulations up to 4 inches (10 cm). Afterwards, it began to morph into a nor'easter as it moved off the Southeast coast late on January 6, while producing blizzard conditions in the Carolinas. It then began to affect the Northeastern United States as it tracked northwards early on January 7. It produced a swath of moderate snowfall accumulations up the East Coast, with easternmost areas such as parts of Massachusetts receiving up to 1.5 feet (18 in) of snow.
The January 2017 North American ice storm was a major ice storm that impacted the Great Plains, Pacific Northwest, and American Midwest. During the storm, multiple U.S. states declared states of emergency, and icy road conditions caused traffic incidents and fatalities. It was Named Winter Storm Jupiter by the weather channel. An outbreak of 11 tornadoes also struck Texas, injuring two.
The February 15–20, 2021 North American winter storm, also unofficially referred to as Winter Storm Viola, was a significant and widespread snow and ice storm across much of the United States, Northern Mexico, and Southern Canada. The system started out as a winter storm on the West Coast of the United States on February 15, later moving southeast into the Southern Plains and Deep South from February 16–17. It then moved into the Appalachian Mountains and Northeastern United States, before finally moving out to sea on February 20. The storm subsequently became a powerful low pressure system over the North Atlantic, before eventually dissipating on February 26.
