Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time. A season is one of the major divisions of the Year, generally based on yearly periodic changes in Weather. Spring is one of the four Temperate Seasons Spring marks the transition from Winter into Summer. Summer is one of the four Temperate Seasons Summer marks the warmest time of year with the longest days Autumn (also known as fall in North American English) is one of the four Temperate Seasons Autumn marks the transition from Summer Winter is one of the four Seasons of Temperate zones Calculated astronomically, it begins on the Solstice and ends on the Equinox The Tropics are centered on the Equator and limited in Latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23 The dry season is a term commonly used when describing the weather in the Tropics. A wet season or rainy season is a Season in which the average Rainfall in a region is significantly increased A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface and strongly implying Severe weather. A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low 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 A blizzard is a severe Winter storm condition characterized by low Temperatures strong Winds and heavy blowing Snow Blizzards are formed when An ice storm is a type of Winter storm characterized by Freezing rain. In Meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground Drizzle (also called mizzle) is light precipitation consisting of liquid water drops smaller than that of Rain, and generally smaller than 0 Rain is Liquid precipitation. On Earth it is the condensation of atmospheric Water vapor into drops heavy enough to fall often making it to Freezing rain is a type of precipitation that begins as Snow at higher altitude falling from a Cloud towards earth melts completely on its way down while passing Ice pellets are a form of precipitation consisting of small Translucent ice balls Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones Graupel (also called snow pellets) refers to precipitation that forms when supercooled Droplets of Water condense on a Snowflake forming This is a list of meteorology topics. The terms relate to Meteorology, the Interdisciplinary scientific study of the atmosphere that focuses on Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of Air pollution is the human introduction into the atmosphere of Chemicals Particulate matter, or Biological materials that cause harm or discomfort In Meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Water is a common Chemical substance that is essential for the survival of all known forms of Life. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another Planetary body The process of precipitation is called snowfall.

Since snow is composed of small ice particles, it is a granular material. A granular material is a conglomeration of discrete Solid, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would It has an open and therefore soft structure, unless packed by external pressure. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The METAR code for snow is SN. METAR (METeorological Aviation Report is a format for reporting Weather information

Snowflakes

Animation of snowcover changing with the seasons

Trees covered with snow

Snow forms when water vapor condenses directly into ice crystals, usually in a cloud. Ice crystals - small crystalline form of Ice including hexagonal columns hexagonal plates dendritic crystals and Diamond dust. A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another Planetary body Floating cloud particles (ice nucleators, often of biological origin ^[1]) are needed in order for snowflakes to form at temperatures above -40C. An ice nucleus is a particle which acts as the nucleus for the formation of an Ice crystal in the atmosphere. 85% of these nuclei are airborne bacteria, with dust particles making up the rest. ^[2] The ice crystals which form around the ice nucleators typically have a diameter of several milimetres and usually have six lines of symmetry. A snowflake is an aggregate of such ice crystals and may be several centimeters large^[3]. The term "snowflake" is also used below for the symmetrical ice crystals themselves. The individual ice crystals are clear but because of the amount of light the individual crystals reflect snowflakes appear white in color unless contaminated by impurities.

Geometry

Symmetry of an idealized snowflake

The first of a magnification series of a snow crystal (view the entire series) using a low temperature scanning electron microscope

Large, well formed snowflakes are relatively flat and have six approximately identical arms, so that the snowflake nearly has the same 6-fold dihedral symmetry as a regular hexagon or hexagram. In Mathematics, a dihedral group is the group of symmetries of a Regular polygon, including both rotations and reflections General properties These properties apply to both convex and star regular polygons Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees For symbols used in the I Ching, see Hexagram (I Ching For a Jewish symbol see Star of David. This symmetry arises from the hexagonal crystal structure of ordinary ice. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. Ice Ih is the hexagonal crystal form of ordinary Ice, or frozen water. However, the exact shape of the snowflake is determined by the temperature and humidity at which it forms. ^[3]. Rarely, at a temperature of around −2 °C (28 °F), snowflakes can form in threefold symmetry — triangular snowflakes. ^[4] Snowflakes are not perfectly symmetrical however. The most common snowflakes are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing.

Snowflakes can come in many different forms, including columns, needles, bricks and plates (with and without "dendrites" - the "arms" of some snowflakes). A crystal dendrite is a crystal that develops with a typical multi-branching tree-like form These different forms arise out of different temperatures and water saturation - among other conditions. Six petaled ice flowers grow in air between 0 °C (32 °F) and −3 °C (27 °F). The vapor droplets solidify around a dust particle. Between temperatures of −1 °C (30 °F) and −3 °C (27 °F), the snowflake will be in the form of a dendrite or a plate or the six petaled ice flower. As temperatures get colder, between −5 °C (23 °F) and −10 °C (14 °F), the crystals will form in needles or hollow columns or prisms. When the temperature becomes even colder from −10 °C (14 °F) to −22 °C (−8 °F) the ice flowers are formed again, and at temperatures below −22 °C (−8 °F), the vapors will turn into prisms again. If a crystal has started forming at around −5 °C (23 °F), and is then exposed to warmer or colder temperatures, a capped column may be formed which consists of a column-like design capped with a dendrite or plate-like design on each end of the column. ^[3] At even colder temperatures, the snowflake design returns to the more common dendrite and plate. At temperatures approaching −20 °C (−4 °F), sectored plates are formed which appears as a dendrite, with each dendrite appearing flattened, like the design of a snowflake plate. ^[3]

Snowflakes by Wilson Bentley, 1902

There are, broadly, two possible explanations for the symmetry of snowflakes. Wilson Alwyn "Snowflake" Bentley ( February 9, 1865 – December 23, 1931 born at Jericho in the U First, there could be communication or information transfer between the arms, such that growth in each arm affects the growth in each other arm. Surface tension or phonons are among the ways that such communication could occur. For the work of fiction see Surface Tension (short story. Surface tension is a property of the surface of a Liquid that causes it to In Physics, a phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the Atomic lattice of a Solid The other explanation, which appears to be the prevalent view, is that the arms of a snowflake grow independently in an environment that is believed to be rapidly varying in temperature, humidity and other atmospheric conditions. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. This environment is believed to be relatively spatially homogeneous on the scale of a single flake, leading to the arms growing to a high level of visual similarity by responding in identical ways to identical conditions, much in the same way that unrelated trees respond to environmental changes by growing near-identical sets of tree rings. Dendrochronology (from Greek grc δένδρον dendron, "tree" grc χρόνος khronos, "time" and grc -λογία The difference in the environment in scales larger than a snowflake leads to the observed lack of correlation between the shapes of different snowflakes. The sixfold symmetry happens because of the basic hexagonal crystalline structure from which the snowflake grows. Generally speaking an object with rotational symmetry is an object that looks the same after a certain amount of Rotation. The exact reason for the threefold symmetry of triangular snowflakes is still a mystery although trigonal symmetry is a subsymmetry of hexagonal. In Crystallography, the rhombohedral (or trigonal) Crystal system is one of the seven lattice point groups named after the two-dimensional In Crystallography, the hexagonal is one of the 7 Crystal system, it contains 7 Point groups.

There is a widely held belief that no two snowflakes are alike. Strictly speaking, it is extremely unlikely for any two macroscopic objects in the universe to contain an identical molecular structure; but there are, nonetheless, no known scientific laws that prevent it. Macroscopic is commonly used to describe physical objects that are measurable and observable by the Naked eye. In a more pragmatic sense, it's more likely—albeit not much more—that two snowflakes are virtually identical if their environments were similar enough, either because they grew very near one another, or simply by chance. The American Meteorological Society has reported that matching snow crystals were discovered in Wisconsin in 1988 by Nancy Knight of the National Center for Atmospheric Research. The American Meteorological Society ( AMS) promotes the development and dissemination of information and education on the atmospheric and related oceanic The National Center for Atmospheric Research ( NCAR) is a non-governmental U The crystals were not flakes in the usual sense but rather hollow hexagonal prisms. Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees General right and uniform prisms A right prism is a prism in which the joining edges and faces are perpendicular to the base faces

Snowflakes

Snow on the ground

Snow in the city of Rovaniemi, Finland

Record breaking snowfall March 2008 at Aubrey, Texas

Snow remains on the ground until it melts or sublimes. History There has probably been continuous settlement in the Rovaniemi area since the Stone Age. Finland, officially the Republic of Finland ( is a Nordic country situated in the Fennoscandian region of northern Europe. Aubrey is a city in Denton County, Texas, United States. The population was 1500 at the 2000 census Melting is a process that results in the phase change of a substance from a Solid to a Liquid. Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage In colder climates this results in snow lying on the ground all winter; when the snow does not all melt in the summer it becomes glaciers. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period.

This is often called snowpack, especially when it does persist a long time. The deepest snowpacks occur in mountainous regions. A mountain is a Landform that extends above the surrounding Terrain in a limited area with a peak It is influenced by temperature and wind events which determine melting, accumulation and wind erosion.

The water equivalent of the snow is the thickness of a layer of water having the same content. For example, if the snow covering a given area has a water equivalent of 50 centimetres (20 in), then it will melt into a pool of water 50 centimetres (20 in) deep covering the same area. This is a much more useful measurement to hydrologists than snow depth, as the density of cool freshly fallen snow widely varies. Hydrology (from Greek Yδωρ hudōr, "water" and λόγος logos, "study" is the study of the movement distribution and quality of New snow commonly has a density of between 5% and 15% of water. Snow that falls in maritime climates is usually denser than snow that falls in mid-continent locations because of the higher average temperatures over oceans than over land masses. Cloud temperatures and physical processes in the cloud affect the shape of individual snow crystals. Highly branched or dendritic crystals tend to have more space between the arms of ice that form the snow flake and this snow will therefore have a lower density, often referred to as "dry" snow. Conditions that create columnar or platelike crystals will have much less air space within the crystal and will therefore be more dense and feel "wetter".

First snow of winter, Truckee, California, United States

Once the snow is on the ground, it will settle under its own weight (largely due to differential evaporation) until its density is approximately 30% of water. Truckee is an incorporated town in Nevada County, California, United States. Increases in density above this initial compression occur primarily melting and refreezing, caused by temperatures above freezing or by direct solar radiation. By late spring, snow densities typically reach a maximum of 50% of water. ^[5]

Spring snow melt is a major source of water supply to areas in temperate zones near mountains that catch and hold winter snow, especially those with a prolonged dry summer. A Mediterranean climate is one that resembles the Climate of the lands in the Mediterranean Basin, which includes over half of the area with this climate type world-wide In such places, water equivalent is of great interest to water managers wishing to predict spring runoff and the water supply of cities downstream. Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows Water supply is the process of self-provision or provision by third parties of water of various qualities to different users Measurements are made manually at marked locations known as snow courses, and remotely using special scales called snow pillows.

Many rivers originating in mountainous or high-latitude regions have a significant portion of their flow from snowmelt. This often makes the river's flow highly seasonal resulting in periodic flooding. A flood is an overflow of an expanse of water that submerges land a deluge In contrast, if much of the melt is from glaciated or nearly glaciated areas, the melt continues through the warm season, mitigating that effect. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period.

Energy balance

The energy balance of the snowpack is dictated by several heat exchange processes. The snowpack absorbs solar shortwave radiation that is partially blocked by cloud cover and reflected by snow surface. A longwave heat exchange takes place between the snowpack and its surrounding environment that includes overlaying air mass, tree cover and clouds. Convective (sensible) heat exchange between the snowpack and the overlaying air mass is governed by the temperature gradient and wind speed. Moisture exchange between the snowpack and the overlaying air mass is accompanied with latent heat transfer that is influenced by vapor pressure gradient and air wind. Rain on snow could induce significant heat input to the snowpack. A generally insignificant conductive heat exchange takes place between the snowpack and the underlying ground. That is the reason there is a small temperature rise after or before the snowfall. ^[6]

Effects on human society

Section of an icehouse

Activity

Substantial snowfall can disrupt public infrastructure and services, slowing human activity even in regions that are accustomed to such weather. Ice houses were buildings used to store Ice throughout the year prior to the invention of the Refrigerator. Air and ground transport may be greatly inhibited or shut down entirely. Populations living in snow-prone areas have developed various ways to travel across the snow, such as skis, snowshoes, and sleds pulled by horses, dogs, or other animals. A ski is a long flat device worn on the feet designed to help the wearer slide smoothly over snow Development of snowshoes Origins Before humanity built snowshoes nature provided examples A sled, sledge or sleigh is a Vehicle with runners for sliding instead of wheels for rolling Basic infrastructures such as electricity, telephone lines, and gas supply can also fail. Electricity distribution is the penultimate stage in the delivery (before retail) of Electricity to end users A telephone line or telephone circuit (or just line or circuit within the Industry) is a single-user circuit on a Telephone Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, In addition, snow can make roads much harder to travel and cars attempting to traverse them can easily become stuck. The combined effects can lead to a "snow day" on which gatherings such as school, work, or church are officially canceled. Weather-related cancellation or sometimes a delay is when an institution is closed or its opening delayed or an activity is cancelled or postponed due to inclement Weather In areas that normally have very little or no snow, a snow day may occur when there is only light accumulation or even the threat of snowfall, since those areas are ill-prepared to handle any amount of snow.

Agriculture

Snowfall can be beneficial to agriculture by serving as a thermal insulator, conserving the heat of the Earth and protecting crops from subfreezing weather. The term thermal insulation can refer to materials used to reduce the rate of Heat transfer, or the methods and processes used to reduce heat transfer Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture Some agricultural areas depend on an accumulation of snow during winter that will melt gradually in spring, providing water for crop growth.

Conservation

In areas near mountains, people have harvested snow and stored it as layers of ice covered by straw or sawdust in icehouses. Straw is an agricultural By-product, the dry stalk of a Cereal plant after the Grain or Seed has been removed Sawdust is composed of fine particles of Wood. This material is produced from cutting with a Saw, hence its name Ice houses were buildings used to store Ice throughout the year prior to the invention of the Refrigerator. This allowed the ice to be used in summer for refrigeration or medical uses.

Damage

A mudslide, flash flood, or avalanche can occur when excessive snow has accumulated on a mountain and there is a sudden change of temperature. Mudslide redirects here it is also the name of a cocktail. A mudflow or mudslide is the most rapid (up to 80 km/h / 50 mph A flash flood is a rapid flooding of geomorphic lowlying areas - washes rivers and streams This article refers to the natural event For other uses see Avalanche (disambiguation An avalanche is an abrupt and rapid flow of snow often Large amounts of snow that accumulate on top of man-made structures can lead to structural failure.

Records

The highest seasonal total snowfall ever measured was at Mount Baker Ski Area, outside of the town Bellingham, Washington in the United States during the 1998–1999 season. The Mount Baker Ski Area is a Ski resort located in Whatcom County Washington, United States. Bellingham, Washington is the County seat of Whatcom County in the U The United States of America —commonly referred to as the Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Mount Baker received 1,140 inches (29 m) of snow,^[7] thus surpassing the previous record holder, Mount Rainier, Washington, which during the 1971–1972 season received 1,122 in. Mount Rainier is an active Stratovolcano (also known as a composite volcano in Pierce County Washington, located southeast of Seattle, Washington Washington ( is a state in the Pacific Northwest region of the United States. Year 1971 ( MCMLXXI) was a Common year starting on Friday (link will display full calendar of the 1971 Gregorian calendar. Year 1972 ( MCMLXXII) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. (28. 5 m) of snow. ^[8] Guinness World Records list the world’s largest snowflakes as those of January 1887 at Fort Keogh, Montana;. allegedly one measured 15 inches (38 cm) wide. ^[9]

Recreation

Building a snowman. A snowman is an Anthropomorphic snow sculpture History In Occidental cultures and the northern hemisphere, snowmen are considered

• Many winter sports, such as skiing, snowboarding, snowmobiling and snowshoeing depend on snow. A winter sport is a Sport commonly played during Winter. As a formal term it refers to a sport played on Snow or Ice, but informally can refer Snow skiing is a group of sports utilizing Skis as primary equipment Snowboarding is a sport that involves descending a Snow -covered slope on a Snowboard attached to a participant's feet using a special boot set into a mounted binding A snowmobile (known locally as snowmachine, snowsled or by the Brandname Ski-Doo) is a land vehicle that is commonly propelled by Development of snowshoes Origins Before humanity built snowshoes nature provided examples Where snow is scarce but the temperature is low enough, snow cannons may be used to produce an adequate amount for such sports.
• Children can play on a sled or ride in a sleigh. A sled, sledge or sleigh is a Vehicle with runners for sliding instead of wheels for rolling A sled, sledge or sleigh is a Vehicle with runners for sliding instead of wheels for rolling
• Snow can be sculptured into snowmen, used to trace the motion of a person's body (snow angels), or formed into snowballs for throwing or for having snowball fights. Snow sculpture is a Sculpture form comparable to Sand sculpture or Ice sculpture in that most of it is now practiced outdoors and often in full view of A snowman is an Anthropomorphic snow sculpture History In Occidental cultures and the northern hemisphere, snowmen are considered A snow angel is a human-made depression formed in an area of Snow in the shape of an Angel. A snowball is a spherical object made from frozen water or Snow, usually created by scooping snow with the hands and compacting it into a roughly fist-sized A snowball fight is a physical Game often played by young people in which Snowballs are thrown with the intention of hitting somebody else
• Snow can be used to build defensive snow forts for outdoor games such as Capture the flag. snow fort or snow castle is a usually open-topped temporary structure made of Snow walls that is used for recreational purposes Capture the flag ( CTF) is a traditional outdoor sport often played by children or sometimes adults where two teams each have a flag (or other marker and the objective is
• The world's biggest snowcastle, the SnowCastle of Kemi, is built in Kemi, Finland every winter. The SnowCastle of Kemi is the biggest Snow Castle in the world Kemi (Giepma is a town and municipality of Finland. It is located very near of the city of Tornio. Finland, officially the Republic of Finland ( is a Nordic country situated in the Fennoscandian region of northern Europe.
• Since 1928 Michigan Technological University in Houghton, Michigan has held an annual Winter Carnival in mid-February, during which a large Snow Sculpture Contest takes place between various clubs, fraternities, and organizations in the community and the university. Michigan Technological University ( abbr Michigan Tech or MTU) is an American Public university with a range of degree offerings Houghton is a City in the US state of Michigan 's Upper Peninsula and largest city in the Copper Snow sculpture is a Sculpture form comparable to Sand sculpture or Ice sculpture in that most of it is now practiced outdoors and often in full view of Each year there is a central theme, and prizes are awarded based on creativity.

Types of snow

Hoar frost that grows on the snow surface due to water vapor moving up through the snow on cold, clear nights

Falling snow

Blizzard

A long-lasting snow storm with intense snowfall and usually high winds. Frost is the solid deposition of Water vapor from saturated air A blizzard is a severe Winter storm condition characterized by low Temperatures strong Winds and heavy blowing Snow Blizzards are formed when Particularly severe storms can create whiteout conditions where visibility is reduced to less than 1 m. Whiteout is a Weather condition in which visibility and contrast are severely reduced by Snow and diffuse lighting from overcast Clouds There are three

Columns

A class of snow flakes that is shaped like a six sided column. A column in Structural engineering is a vertical structural element that transmits through compression, the weight of the structure above to other structural One of the 4 classes of snow flakes.

Dendrites

A class of snow flakes that has 6 points, making it somewhat star shaped. A crystal dendrite is a crystal that develops with a typical multi-branching tree-like form The classic snow flake shape. One of the 4 classes of snow flakes.

Flurry

A period of light snow with usually little accumulation with occasional moderate snowfall.

Freezing rain

Supercooled rain that freezes on impact with a sufficiently cold surface. Freezing rain is a type of precipitation that begins as Snow at higher altitude falling from a Cloud towards earth melts completely on its way down while passing This can cover trees in a uniform layer of very clear, shiny ice – a beautiful phenomenon, though excessive accumulation can break tree limbs and utility lines, causing utility failures and possible property damage.

Snowbird ski resort, one of the snowiest places in the U. Snowbird is a year-round ski and summer resort located in the U S.

Graupel

Precipitation formed when freezing fog condenses on a snowflake, forming a ball of rime ice. Graupel (also called snow pellets) refers to precipitation that forms when supercooled Droplets of Water condense on a Snowflake forming Also known as snow pellets.

Ground blizzard

Occurs when a strong wind drives already fallen snow to create drifts and whiteouts. Ground blizzard refers to a Weather condition where loose snow or ice on the ground is lifted and blown by strong winds

Hail

Many-layered ice balls, ranging from "pea" sized (0. Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones 25 in, 6 mm) to "golf ball" sized (1. 75 in, 43 mm), to, in rare cases, "softball" sized or greater (­>4. 25 in, 108 mm).

Hailstorm

A storm of hail. Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones If the hail is sufficiently large, it can cause damage to cars or even people.

Lake effect snow

Produced when cold winds move across long expanses of warmer lake water, picking up water vapor which freezes and is deposited on the lake's shores. Lake-effect snow is produced in the winter when cold Arctic winds move across long expanses of warmer lake water providing energy and picking up Water vapor which freezes

Needles

A class of snow flakes that are acicular in shape (their length is much longer than their diameter, like a needle). One of the 4 classes of snow flakes.

Rimed snow

Snow flakes that are partially or completely coated in tiny frozen water droplets called rime. Rime forms on a snow flake when it passes through a super-cooled cloud. One of the 4 classes of snow flakes.

Sleet

In Britain, rain mixed with snow; Some Americans also refer to this as sleet, while others refer to sleet as ice pellets formed when snowflakes pass through a layer of warm air, partially or completely thaw, then refreeze upon passing through sufficiently cold air during further descent. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located

Snow on trees in DuBois, Pennsylvania. DuBois (duːˈbɔɪz doo-BOYS or /ˈduːbɔɪz/ DOO-boys, not /duːˈbwɑː/ doo-BWAH) is a City in Clearfield County,

Snow pellets

See graupel.

Snow squall

A brief, very intense snowstorm. A snowsquall is a sudden moderately heavy Snow fall with Blowing snow and strong gusty surface Winds ref> National Weather Service Detroit/Pontiac

Snow storm

A long storm of relatively heavy snow. 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 A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface and strongly implying Severe weather.

Soft hail

See graupel. Graupel (also called snow pellets) refers to precipitation that forms when supercooled Droplets of Water condense on a Snowflake forming

Thundersnow

A thunderstorm which produces snow as the primary form of precipitation. Thundersnow also known as a winter thunderstorm or a thunder snowstorm is a rare Thunderstorm with Snow falling as the primary precipitation

Wintry mix

Precipitation consisting of both snow and rain.

Snow on the ground

Snow covering a leaf

Snow blowing from a roof in Ottawa

Artificial snow

Snow can be also manufactured using snow cannons, which actually create tiny granules more like soft hail (this is sometimes called "grits" by those in the southern U.S. for its likeness to the texture of the food). Ottawa (ˈɒtəwə or sometimes /ˈɒtəwɑː/ is the Capital of Canada and the country's fourth largest municipality. The Southern United States &mdashcommonly referred to as the American South, Dixie, or simply the South &mdashconstitutes a large distinctive GRITS is a Christian hip hop group from Nashville, Tennessee. In recent years, snow cannons have been produced that create more natural-looking snow, but these machines are prohibitively expensive.

Blowing snow

Snow on ground that is being moved around by wind. See ground blizzard. Ground blizzard refers to a Weather condition where loose snow or ice on the ground is lifted and blown by strong winds

Chopped powder

Powder snow that has been cut up by previous skiers.

Corn

Coarse, granular wet snow. Most commonly used by skiers describing good spring snow. Corn is the result of diurnal cycle of melting and refreezing.

Cornice

An overhanging formation of windblown snow. Important in skiing and alpine climbing because the overhang can be unstable and hard to see from the leeward side.

Crud

This covers varieties of snow that all but advanced skiers find impassable. Subtypes are (a) windblown powder with irregularly shaped crust patches and ridges, (b) heavy tracked spring snow re-frozen to leave a deeply rutted surface strewn with loose blocks, (c) a deep layer of heavy snow saturated by rain (although this may go by another term). Crud is negotiated with a even weighting along the length of the skis, and smooth radius turns started, if necessary, with a pop or jump. When an advanced skier falls over on crud, it is probably because it is 'heavy crud', q. v.

Crust

A layer of snow on the surface of the snowpack that is stronger than the snow below, which may be powder snow. Depending on their thickness and resulting strength, crusts can be termed "supportable," meaning that they will support the weight of a human, "breakable," meaning that they will not, or "zipper," meaning that a skier can break and ski through the crust. Crusts often result from partial melting of the snow surface by direct sunlight or warm air followed by re-freezing.

Depth Hoar

Faceted snow crystals, usually poorly or completely unbonded (unsintered) to adjacent crystals, creating a weak zone in the snowpack. Depth hoar forms from metamorphism of the snowpack in response to a large temperature gradient between the warmer ground beneath the snowpack and the surface. The relatively high porosity (percentage of air space), relatively warm temperature (usually near freezing point), and unbonded weak snow in this layer can allow various organisms to live in it.

Finger Drift

A narrow snow drift(1-3 feet in width) crossing a roadway. Several finger drifts in succession resemble the fingers of a hand.

Heavy crud

See 'Crud'.

Ice

Densely packed material formed from snow that doesn't contain air bubbles. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Depending on the snow accumulation rate, the air temperature, and the weight of the snow in the upper layers, it can take snow a few hours or a few decades to form into ice.

Firn

Snow which has been lying for at least a year but which has not yet consolidated into glacier ice. It is granular.

Packed Powder

The most common snow cover on ski slopes, consisting of powder snow that has lain on the ground long enough to become compressed, but is still loose.

Packing snow

Snow that is at or near the melting point, so that it can easily be packed into snowballs and hurled at other people or objects. This is perfect for snow fights and other winter fun, such as making a snowman, or a snow fort.

Penitentes

Tall blades of snow found at high altitudes. Penitentes are a snow formation found at high altitudes They take the form of tall thin blades of hardened snow or ice closely spaced with the blades oriented towards the general

Pillow Drift

A snow drift crossing a roadway and usually 10-15 feet in width and 1-3 three feet in depth.

Powder

Freshly fallen, uncompacted snow. The density and moisture content of powder snow can vary widely; snowfall in coastal regions and areas with higher humidity is usually heavier than a similar depth of snowfall in an arid or continental region. Light, dry (low moisture content, typically 4 - 7% water content) powder snow is prized by skiers and snowboarders. It is often found in the Rocky Mountains of North America and in Niseko, Japan. Mountain peaks of the Rocky Mountains The Rocky Mountains, often called the Rockies, are a Mountain range in western North America.

The textures of a snowdrift on the Long Mynd, Shropshire

Slush

Snow which partially melts upon reaching the ground, to the point that it accumulates in puddles of partially-frozen water. The Long Mynd in Shropshire, England, is a part of the Shropshire Hills Area of Outstanding Natural Beauty. Shropshire (ˈʃrɒpʃɪə/ /-ʃə alternatively known as Salop or abbreviated in print only Shrops, is a county in the This article is about the mixture of solid and liquid snow For other uses of the term "slush" see Slush (disambiguation.

Snirt

Snow that is dirty, often seen by the side of roads and parking lots that have been plowed.

Snowdrift

Large piles of snow which occur near walls and curbs, as the wind tends to push the snow up toward the vertical surfaces. A snowdrift is a deposit of Snow created by Wind into a mound during Snowstorms They resemble Sand dunes and are formed in a similar manner

Surface Hoar

Faceted, corn-flake shaped snow crystals that are a type of frost that forms on the surface of the snow pack on cold, clear, calm nights. Subsequent snow fall can bury layers of surface hoar encorporating them into the snowpack where they can form a weak layer. Sometimes referred to as hoar frost. Frost is the solid deposition of Water vapor from saturated air

Watermelon snow

A reddish/pink colored snow that smells like watermelons, and is caused by a red colored green algae called Chlamydomonas nivalis. Watermelon snow, also called snow algae, is Snow that is reddish or pink in color with the slight scent of a fresh Watermelon. Watermelon ( Citrullus lanatus ( Thunb) Matsum & Nakai family Cucurbitaceae) refers to both Fruit and Plant of a vine-like (climber The green algae (singular green alga) are the large group of Algae from which the Embryophytes (higher plants emerged Watermelon snow, also called snow algae, is Snow that is reddish or pink in color with the slight scent of a fresh Watermelon.

Wind slab

A layer of relatively stiff, hard snow formed by deposition of wind blown snow on the leeward side of a ridge or other sheltered area. Wind slabs can form over weaker, softer freshly fallen powder snow creating an avalanche hazard on steep slopes.

See also

References

External links

• Snowpack energy and mass balance An article that contains detailed analysis of snowpack energy and mass balance.
• Ultra-high resolution images of snowflakes, hosted by the Electron Microscopy Unit of the USDA Beltsville Agricultural Research Center
• Snow at above freezing temperatures
• Kenneth G. Libbrecht - Snowflake FAQ
• United Nations Environment Programme: Global Outlook for Ice and Snow