Rain and snow mixed (known as sleet outside the United States) is precipitation composed of rain and partially melted snow. This precipitation can occur where the temperature in the lower part of the atmosphere is slightly above the freezing point (0 °C, 32 °F). The METAR code for this precipitation is RASN.
This precipitation is soft (unlike ice pellets) and translucent, but it can contain some traces of ice crystals, due to partially fused snowflakes. It is usually a transition phase from rain to snow or vice versa.
"Wintry showers" or "wintry mixes"
Wintry showers is a somewhat informal meteorological term, used primarily in the United Kingdom, to refer to various mixtures of rain, graupel and snow. Professional meteorologists tend to shy away from using the term under any circumstances, but radio and television weather reporters use it regularly.
Though no "official" criteria exist for the term, in the United Kingdom the term is not used when any accumulation of snow on the ground takes place. It is often used when the temperature of the ground surface is above 0 °C, preventing accumulation from occurring even if the air temperature is marginally below 0 °C; but even then the falling precipitation must generally be something other than consisting exclusively of snow.
In the United States, wintry mix generally refers to a mixture of freezing rain, ice pellets, and snow. In contrast to the usage in the United Kingdom, in the United States it is usually used when air and ground temperatures are below 0 °C. Additionally, it is generally used when some accumulation of ice and snow is expected to occur. During the winter season, a large area can be impacted by the multiple precipitation types typical of a wintry mix during a single winter storm, as counter-clockwise winds around a storm system bring warm air northward ahead of the system, and then bring cold air back southward 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, causing snow to change to 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 change directly from rain to snow, or for it to simply end before transitioning back.
See also
External links
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
