Rain and Snow Mixed

Rain and snow mixed, commonly known as sleet in Commonwealth English, is a type of precipitation characterized by a combination of rain and partially melted snow. This unique weather event produces soft and translucent precipitation that contains traces of ice crystals from partially fused snowflakes, often referred to as slush.

Distinguishing Characteristics

Unlike ice pellets, which are hard, and freezing rain, which is fluid until it freezes upon impact, rain and snow mixed falls in a soft and semi-fluid state. This precipitation usually occurs briefly as a transitional phase between rain and snow or vice versa, hitting the surface before completing the transformation. The METAR code for this phenomenon is RASN or SNRA.

Terminology

While the term sleet is widely used in Commonwealth English-speaking countries, it's essential to note that in the United States, the National Weather Service uses the term sleet to refer specifically to ice pellets.

Formation

The formation of rain and snow mixed is closely linked to temperature conditions in the lowest part of the atmosphere. This precipitation occurs when this temperature is slightly above the freezing point of water (0 °C or 32 °F). The depth of the low-level warm air needed to melt snow falling from above into rain varies, typically ranging from about 230–460 meters (750–1,500 feet). The interaction of the mass of snowflakes and the lapse rate of the melting layer determines when rain and snow will mix, with the precipitation hitting the surface before completing the transformation.

Wintry Showers and Wintry Mixes

• Wintry Showers: A term primarily used in the United Kingdom, wintry showers refer to a mix of rain, graupel, and snow. This informal meteorological term is not used when significant snow accumulation is expected on the ground. It is often applied when the ground surface temperature is above 0 °C (32 °F), preventing snow accumulation, even if the air temperature is marginally below freezing.
• Wintry Mix (United States): In the United States, wintry mix commonly refers to a mixture of freezing rain, ice pellets, and snow. It is used when both air and ground temperatures are below 0 °C (32 °F), and there's an expectation of surface accumulation of ice and snow. During winter storms, a large area can experience various mixed precipitation types due to counterclockwise winds around a storm system, bringing warm air ahead of the system and cold air behind it.

Dealing with Rain and Snow Mixed

Dealing with rain and snow mixed requires precautions similar to those taken in icy conditions. Road surfaces can become slippery, so it's crucial to drive cautiously. Pedestrians should be mindful of slippery sidewalks and take measures to prevent slipping. Additionally, staying updated with weather forecasts and advisories is essential to plan activities and travel accordingly during these mixed precipitation events.