Ice storm

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An ice storm is a type of winter storm characterized by freezing rain, also known as a glaze event or, in some parts of the United States, as a silver thaw. [1] The U.S. National Weather Service defines an ice storm as a storm which results in the accumulation of at least 0.25-inch (6.4 mm) of ice on exposed surfaces. [2] From 1982 to 1994, ice storms were more common than blizzards in the U.S., averaging 16 per year. [3] They are generally not violent storms but instead are commonly perceived as gentle rains occurring at temperatures just below freezing.

A winter storm is an event in which varieties of precipitation are formed that only occur at low temperatures, such as snow or sleet, or a rainstorm where ground temperatures are low enough to allow ice to form. In temperate continental climates, these storms are not necessarily restricted to the winter season, but may occur in the late autumn and early spring as well. Very rarely, they may form in summer, though it would have to be an abnormally cold summer, such as the summer of 1816 in the Northeastern United States.

Freezing rain is the name given to rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow, ice pellets, or hail, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter, including the ground, trees, electrical wires, aircraft, and automobiles. The resulting ice, called glaze ice, can accumulate to a thickness of several centimeters and cover all exposed surfaces. The METAR code for freezing rain is FZRA.

Blizzard type of snowstorm

A blizzard is a severe snowstorm characterized by strong sustained winds of at least 56 km/h (35 mph) and lasting for a prolonged period of time—typically three hours or more. 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.



A graph showing the formation of different kinds of precipitation. Precipitation by type.png
A graph showing the formation of different kinds of precipitation.

The formation of ice begins with a layer of above-freezing air above a layer of sub-freezing temperatures closer to the surface. Frozen precipitation melts to rain while falling into the warm air layer, and then begins to refreeze in the cold layer below. If the precipitate refreezes while still in the air, it will land on the ground as sleet. Alternatively, the liquid droplets can continue to fall without freezing, passing through the cold air just above the surface. This thin layer of air then cools the rain to a temperature below freezing (0 °C or 32 °F). However, the drops themselves do not freeze, a phenomenon called supercooling (or forming "supercooled drops"). When the supercooled drops strike ground or anything else below 0 °C (32 °F) (e.g. power lines, tree branches, aircraft), a layer of ice accumulates as the cold water drips off, forming a slowly thickening film of ice, hence freezing rain. [4] [5] [6]

Ice pellets are a form of precipitation consisting of small, translucent balls of ice. Ice pellets are smaller than hailstones which form in thunderstorms rather than in winter, and are different from graupel which is made of frosty white rime, and from a mixture of rain and snow which is a slushy liquid or semisolid. Ice pellets often bounce when they hit the ground or other solid objects, and make a higher-pitched "tap" when striking objects like jackets, windshields, and dried leaves, compared to the dull splat of liquid raindrops. Pellets generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL.

Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid.

While meteorologists can predict when and where an ice storm will occur, some storms still occur with little or no warning. [5] In the United States, most ice storms are in the northeastern part of the country, but damaging storms have occurred farther south. An ice storm in February 1994 resulted in tremendous ice accumulation as far south as Mississippi, and caused reported damage in nine states. More timber was damaged than that caused by Hurricane Camille. An ice storm in eastern Washington in November 1996 directly followed heavy snowfall. The combined weight of the snow and 25 to 37 millimeters (0.98 to 1.46 in) of ice caused widespread damage and was considered the most severe ice storm in the Spokane area since 1940. [3]

Hurricane Camille Category 5 Atlantic hurricane in 1969

Hurricane Camille was the second most intense tropical cyclone on record to strike the United States. The most intense storm of the 1969 Atlantic hurricane season, Camille formed as a tropical depression on August 14 south of Cuba from a long-tracked tropical wave. Located in a favorable environment for strengthening, the storm quickly intensified into a Category 2 hurricane before striking the western part of Cuba on August 15. Emerging into the Gulf of Mexico, Camille underwent another period of rapid intensification and became a Category 5 hurricane the next day as it moved northward towards the Louisiana–Mississippi region. Despite weakening slightly on August 17, the hurricane quickly re-intensified back to a Category 5 hurricane before it made landfall in Pass Christian, Mississippi early on August 18, at peak intensity, with a minimum pressure of 900 mbar (26.58 inHg). This was the second-lowest pressure recorded for a US landfall. Only the 1935 Labor Day hurricane had a lower pressure at landfall. As Camille pushed inland, it quickly weakened and was a tropical depression by the time it was over the Ohio Valley. Once it emerged offshore, Camille was able to restrengthen to a strong tropical storm, before it became extratropical on August 22. Camille was subsequently absorbed by a frontal storm over the North Atlantic on the same day.

Eastern Washington Metropolitan area in Washington, United States

Eastern Washington is the portion of the US state of Washington east of the Cascade Range. The region contains the city of Spokane, the Tri-Cities, the Columbia River and the Grand Coulee Dam, the Hanford Nuclear Reservation and the fertile farmlands of the Yakima Valley and the Palouse. Unlike in Western Washington, the climate is dry, including some desert environments.

Washington (state) State of the United States of America

Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. Named for George Washington, the first president of the United States, the state was made out of the western part of the Washington Territory, which was ceded by Britain in 1846 in accordance with the Oregon Treaty in the settlement of the Oregon boundary dispute. It was admitted to the Union as the 42nd state in 1889. Olympia is the state capital; the state's largest city is Seattle. Washington is sometimes referred to as Washington State to distinguish it from Washington, D.C., the capital of the United States.


Power lines sagging after an ice storm. Besides disrupting transportation, ice storms can disrupt utilities by snapping lines and poles. Ice storm.jpg
Power lines sagging after an ice storm. Besides disrupting transportation, ice storms can disrupt utilities by snapping lines and poles.

The freezing rain from an ice storm covers everything with heavy, smooth glaze ice. In addition to hazardous driving or walking conditions, branches or even whole trees may break from the weight of ice. Falling branches can block roads, tear down power and telephone lines, and cause other damage. Even without falling trees and tree branches, the weight of the ice itself can easily snap power lines and also break and bring down power/utility poles; even electricity pylons with steel frames. This can leave people without power for anywhere from several days to a month. According to most meteorologists, just one quarter of an inch of ice accumulation can add about 500 pounds (230 kg) of weight per line span. Damage from ice storms is easily capable of shutting down entire metropolitan areas.

Devastation caused by an ice storm Ice Storm by NOAA.jpg
Devastation caused by an ice storm

Additionally, the loss of power during ice storms has indirectly caused numerous illnesses and deaths due to unintentional carbon monoxide (CO) poisoning. At lower levels, CO poisoning causes symptoms such as nausea, dizziness, fatigue, and headache, but high levels can cause unconsciousness, heart failure, and death. [7] The relatively high incidence of CO poisoning during ice storms occurs due to the use of alternative methods of heating and cooking during prolonged power outages, common after severe ice storms. [8] Gas generators, charcoal and propane barbecues, and kerosene heaters contribute to CO poisoning when they operate in confined locations. [7] CO is produced when appliances burn fuel without enough oxygen present, [9] such as basements and other indoor locations.

Propane is a three-carbon alkane with the molecular formula C3H8. It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel. Propane is one of a group of liquefied petroleum gases (LP gases). The others include butane, propylene, butadiene, butylene, isobutylene, and mixtures thereof.

Kerosene heater

A kerosene heater, also known as a paraffin heater, is typically a portable, unvented, kerosene-fueled, space heating device. In Japan and other countries, they are a primary source of home heat. In the United States and Australia, they are a supplemental heat or a source of emergency heat during a power outage. Most kerosene heaters produce between 3.3 and 6.8 kW.

Loss of electricity during ice storms can indirectly lead to hypothermia and even death from hypothermia. It can also lead to ruptured pipes due to water freezing inside the pipes.

Hypothermia A human body core temperature below 35.0°C

Hypothermia is reduced body temperature that happens when a body dissipates more heat than it absorbs. In humans, it is defined as a body core temperature below 35.0 °C (95.0 °F). Symptoms depend on the temperature. In mild hypothermia there is shivering and mental confusion. In moderate hypothermia shivering stops and confusion increases. In severe hypothermia, there may be paradoxical undressing, in which a person removes their clothing, as well as an increased risk of the heart stopping.

Notable ice storms

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Related Research Articles

Hail Form of solid precipitation

Hail is a form of solid precipitation. It is distinct from ice pellets, though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets fall generally in cold weather while hail growth is greatly inhibited during cold surface temperatures.

January 1998 North American ice storm January 1998 storm in North America

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 all over 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 35 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.

A winter storm warning is a statement made by the National Weather Service of the United States which means a winter storm is occurring or is about to occur in the area, usually within 36 hours. Generally, a Winter Storm Warning is issued if the following criteria, at least, are forecast: usually between 4 inches (10 cm) to 7 inches (18 cm) or more of snow or usually 3 inches (7.6 cm) or more of snow with a large accumulation of ice. In the Southern United States, where severe winter weather is much less common and any snow is a more significant event, warning criteria are lower, as low as 1 inch (2.5 cm) in the southernmost areas: as one goes from north to south, the necessary accumulations lessen. A warning can also be issued during high impact events of lesser amounts, usually early or very late in the season when trees have leaves and damage can result. Winter Storm Warnings are issued when winds are less than 35mph; if the storm has winds above this wind speed, it becomes a blizzard warning.

Ice storm warning message issued by the U.S. National Weather Service

An Ice Storm Warning is issued by the National Weather Service of the United States when freezing rain produces a significant and possibly damaging accumulation of ice. The criteria for this warning vary from state to state, but typically an ice storm warning will be issued any time more than 14 inch (6.4 mm) of ice is expected to accumulate in an area; in some areas, the criterion is 12 inch (13 mm).

The December 2005 North American ice storm was a damaging winter storm that produced extensive ice damage in a large portion of the Southern United States from December 14–16, 2005, while extensive snowfall was reported across portions of the Canadian provinces of Ontario and Quebec. The ice storm led to enormous and widespread power outages, and at least 7 deaths.

Freezing drizzle is drizzle that freezes on contact with the ground or an object at or near the surface. Its METAR code is FZDZ.

Lake Storm "Aphid"

The October 2006 Buffalo storm was an unusual early-season lake effect snow storm that hit the Buffalo, New York area and other surrounding areas of the United States and Canada, from the afternoon of Thursday, October 12 through the morning of Friday, October 13, 2006. It was called Lake Storm "Aphid" by the National Weather Service office in Buffalo in accordance with their naming scheme of lake effect snow storms for that year, which related to insects, though locals never used that terminology and have simply referred to it as the October Surprise or the October Storm or Arborgeddon.

Hanukkah Eve windstorm of 2006

The Hanukkah Eve windstorm of 2006 was a powerful Pacific Northwest windstorm in the Pacific Northwest region of the United States and southern British Columbia, Canada between December 14, 2006 and December 15, 2006. The storm produced hurricane-force wind gusts and heavy rainfall, causing hundreds of millions of dollars in damage and leaving over 1.8 million residences and businesses without power. Eighteen people were killed, most of whom died of carbon monoxide poisoning in the days following the storm because of improper use of barbecue cookers and generators indoors. The name of the storm was chosen in a contest run by the National Weather Service office in Seattle from about 8,000 entries.

February 2007 North American blizzard

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.

Glaze (ice) smooth, transparent and homogeneous ice coating occurring when freezing rain or drizzle hits a surface

Glaze or glaze ice, also called glazed frost, is a smooth, transparent and homogeneous ice coating occurring when freezing rain or drizzle hits a surface. It is similar in appearance to clear ice, which forms from supercooled water droplets. It is a relatively common occurrence in temperate climates in the winter when precipitation forms in warm air aloft and falls into below-freezing temperature at the surface.

December 2008 Northeastern United States ice storm

The December 2008 Northeastern United States ice storm was a damaging ice storm that took out power for millions of people in those regions. The storm was deemed the worst ice storm in a decade for New England and the most severe ice storm in 21 years for Upstate New York. Damage was primarily a result of fallen trees and fallen utility wires and poles, which were coated in a heavy layer of ice. The storm raised heavy controversy over the slow return of power, as at the storm's peak as many as 1.7 million customers were without power. Days after the storm more than 800,000 customers were still without power. Almost a week after the storm still more than 100,000 customers were without power, affecting the holiday shopping season and crippling the business and transportation of many northeast cities for days.

January 2009 North American ice storm Ice Storm that occured in 2009

The January 2009 North American ice storm was a major ice storm that impacted parts of Oklahoma, Arkansas, Missouri, Illinois, Indiana, Ohio, West Virginia, tennessee, and Kentucky. The storm produced widespread power outages for over 2 million people due to heavy ice accumulation. The hardest hit areas were in Western Kentucky with over 500,000 residences without power during the height of the storm, including 100,000 without power for over one week, and northern Arkansas, with 300,000 residences without power. This ice storm killed 65 people nationwide, 35 in Kentucky. Most deaths were attributed to carbon monoxide poisoning due to power generators or kerosene heaters being used indoors without proper ventilation. Kentucky Governor Steve Beshear called up the entire Kentucky Army National Guard to deal with the after effects of this storm, the largest National Guard call up in that state's history.

The North American ice storm of January 1961 was a massive ice storm that struck areas of northern Idaho in the United States on January 1–3, 1961. The storm set a record for thickest recorded ice accumulation from a single storm in the United States, at 8 inches.

December 1969 noreaster

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.

North Carolina ice storm of 2002

The North Carolina ice storm of 2002 caused up to an inch of freezing rain from December 4–5 in central North Carolina. A total of 24 people were killed, and as many as 1.8 million people were left without electricity on December 6. Power outages began December 4, and power was not completely restored to until December 14. Raleigh received the most freezing rain from a single storm since 1948, and Bristol, Tennessee received the most ice it had seen in 28 years. The storm also produced heavy rain in both the mountains and coastal plain of North Carolina. Much of the Southern Plains and the Northeast received snow with this system.

December 2013 North American storm complex

The December 2013 North American storm complex was a significant storm complex that had all sorts of severe weather, including a winter storm, a crippling ice storm and a tornado outbreak that impacted the central and eastern portions of Canada, parts of the Central Great Plains, the Southern United States, and the northeastern United States from December 20 to 23, 2013. Formed in the South Central United States, the storm headed across the Great Plains towards Canada into Atlantic Canada and northeastern United States where the storm dissipated on December 23, 2013. The storm produced freezing rain and snow to the affected areas which caused massive damage to electric power transmission and trees. The storm resulted in 27 deaths, loss of power to over a million residents and over $200 million in damages. The storm produced similar conditions to the ice storm of 1998 which affected similar areas.

Mid-February 2014 North American winter storm

The Mid-February 2014 North American winter storm was a major snow and ice storm that affected the American South and East Coast of the United States, bringing with it up to a foot of snow and crippling ice across parts of the South. Thousands if not hundreds of thousands of people were left in the dark for days, possibly even up to 2 weeks without power.

North American ice storm of mid-January 2017 ice storm

The North American ice storm of mid-January 2017 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.


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