Rain and snow mixed is
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
composed of a mixture of
rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...
and partially melted
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
. Unlike
ice pellets, which are hard, and
freezing rain
Freezing rain is 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 or ice pellets, freezing rain is made entirely of liquid droplets. The rain ...
, which is fluid until striking an object where it fully freezes, this precipitation is soft and
translucent
In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions ...
, but it contains some traces of
ice crystals from partially fused snowflakes, also called
slush
Slush, also called slush ice, is a slurry mixture of small ice crystals (e.g., snow) and liquid water.
In the natural environment, slush forms when ice or snow melts or during mixed precipitation. This often mixes with dirt and other polluta ...
. In any one location, it usually occurs briefly as a transition phase from rain to snow or vice versa, but hits the surface before fully transforming. Its
METAR code is RASN or SNRA.
Terminology
This precipitation type is commonly known as sleet in most Commonwealth countries. However, the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
National Weather Service
The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
uses the term ''sleet'' to refer to
ice pellets instead. In
Ithaca, NY, the term Ithacating is used to describe precipitation made of a mix of rain and snow.
Formation
This precipitation occurs when the
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
in the lowest part of the atmosphere is slightly above the
freezing point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depend ...
of water The depth of low-level warm air (below the freezing level) needed to melt snow falling from above to rain varies from about and depends on the mass of the flakes and the
lapse rate of the melting layer. Rain and snow typically mix when the melting layer depth falls between these values as rain starts forming when in that range.
"Wintry showers" or "wintry mixes"
Wintry showers is a somewhat informal meteorological term, used primarily in the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
, to refer to various mixtures of rain,
graupel and snow at once. Though no "official" criteria exist for the term, in the United Kingdom the term is not used when any significant accumulation of snow on the ground takes place. It is often used when the temperature of the ground surface is above , preventing accumulation from occurring even if the air temperature near the surface is marginally below ; but even then, the falling
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
must generally have something else other than exclusively snow.
In the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, wintry mix generally refers to a mixture of
freezing rain
Freezing rain is 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 or ice pellets, freezing rain is made entirely of liquid droplets. The rain ...
,
ice pellets, and snow.
In contrast to the usage in the United Kingdom, in the United States it is usually used when both air and ground temperatures are below . Additionally, it is generally used when some surface accumulation of ice and snow is expected to occur. During winter, a wide area can be affected by the multiple mixed precipitation types typical of a wintry mix during a single winter storm, as counter-clockwise winds around a storm system bring warm air northwards ahead of the system, and then bring cold air back southwards behind it. Most often, it is the region ahead of the approaching storm system which sees the wintry mix, as warm air moves northward and above retreating cold air in a
warm front
A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient. Warm fronts lie within broader troughs of low pressure than cold f ...
, causing snow to change into ice pellets, freezing rain and finally rain. The reverse transition can occur behind the departing low pressure system, though it is more common for precipitation to freeze directly from rain to snow, or for it to stop before a transition back.
See also
*
Freezing rain
Freezing rain is 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 or ice pellets, freezing rain is made entirely of liquid droplets. The rain ...
*
Ice pellets
*
Sleet (disambiguation)
Sleet is a regionally variant term for some meteorological phenomena:
*Ice pellets, pellets of ice composed of frozen raindrops or refrozen melted snowflakes (United States)
* Rain and snow mixed, snow that partially melts as it falls (UK, Irelan ...
*
Slush
Slush, also called slush ice, is a slurry mixture of small ice crystals (e.g., snow) and liquid water.
In the natural environment, slush forms when ice or snow melts or during mixed precipitation. This often mixes with dirt and other polluta ...
*
Winter weather
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 climates, these storms are not necessar ...
References
External links
AMS Glossary
{{DEFAULTSORT:Rain And Snow Mixed
Precipitation
Snow or ice weather phenomena
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