Snow is a type of precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that is pulled down by gravity and deposited on the Earth's surface. The main forms of precipitation include rain, snow, ice pellets, and graupel. It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapour and the water within the Earth's atmosphere The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night. Dry air contains roughly (by volume) 78% nitrogen, 21% in the form of crystalline A crystal or crystalline solid is a solid material, whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is crystallography. The process of crystal formation via mechanisms of crystal growth is called water Water is a ubiquitous chemical substance that is composed of hydrogen and oxygen and is vital for all known forms of life ice Ice is a solid phase, usually crystalline, of a non-metallic substance that is liquid or gas at room temperature, such as water, carbon dioxide ice , ammonia ice, or methane ice. However, the predominant use of the term ice is for water ice, technically restricted to one of the 15 known crystalline phases of water. In non-scientific contexts, the, consisting of a multitude of snowflakes Snowflakes are conglomerations of frozen ice crystals which fall through the Earth's atmosphere. They begin as snow crystals which develop when microscopic supercooled cloud droplets freeze. Snowflakes come in a variety of sizes and shapes. Complex shapes emerge as the flake moves through differing temperature and humidity regimes. Individual that fall from clouds A cloud is a visible mass of droplets, in other words, little drops of water or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae. Clouds are studied in the nephology or. 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 constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations. Thus, the lower size limit for grains in granular material is about 1. It has an open and therefore soft structure, unless packed by external pressure Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Snowflakes come in a variety of sizes and shapes. Types which fall in the form of a ball due to melting and refreezing, rather than a flake, are known as graupel Graupel refers to precipitation that forms when supercooled droplets of water condense on a snowflake, forming a 2–5 mm ball of rime; the snowflake acts as a nucleus of condensation in this process. Graupel is the German word for this meteorological phenomenon, with ice pellets Ice pellets are a form of precipitation consisting of small, translucent balls of ice. Ice pellets usually are smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL and snow grains as examples of graupel. Snowfall amount and its related liquid equivalent precipitation amount are determined using a variety of different rain gauges A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation (as opposed to solid precipitation that is measured by a snow gauge) over a set period of time.
The process of precipitating snow is called snowfall. Snowfall tends to form within regions of upward motion of air around a type of low-pressure system A low pressure area, or "low", is a region where the atmospheric pressure at sea level is lower in relation to surrounding locations. Low pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The name for the process concerning the formation of low pressure areas is known as cyclogenesis known as an extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and horizontal gradients in temperature and dew point. Snow can fall poleward of their associated warm fronts A warm front is defined as the leading edge of an advancing mass of warm air; it separates warm air from the colder air ahead and within their comma head precipitation patterns, which is called such due to its comma-like shape of the cloud and precipitation pattern around the poleward and west sides of extratropical cyclones. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall Lake-effect snow is produced in the winter when cold winds move across long expanses of warmer lake water, providing energy and picking up water vapor which freezes and is deposited on the leeward shores. The same effect over bodies of salt water is called ocean effect snow, sea effect snow, or even bay effect snow. The effect is enhanced when the becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow Thundersnow, also known as a winter thunderstorm or a thunder snowstorm, is a rare thunderstorm with snow falling as the primary precipitation instead of rain. It commonly falls in regions of strong upward motion within the cold sector of extratropical cyclones between autumn and spring when surface temperatures are most likely to be near or below is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy snow is possible where upslope flow is maximized within windward Windward is the direction from which the wind is blowing at the time in question. The side of a ship that is towards the windward is the weather side. If the vessel is heeling under the pressure of the wind, this will be the "higher side" sides of the terrain at elevation, if the atmosphere is cold enough.
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Wall Street Journal
Forecasters said the new storm could bring as much as 10 to 20 inches of snow in Washington, still digging out from a weekend blizzard. ...
More Snow Expected in Mid-Atlantic New York Times
Too Dangerous to Plow, DC, Area Governments Halt Snow Removal FOXNews
More snow keeps government closed in DC Los Angeles Times
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