The why and how of winter precipitation types

Winter storms are no stranger to the east-central Ohio region of Ohio. Even small weak storms can bring multiple types of wintry precipitation to the Valley and each type brings along its own challenges.

By far the most common precipitation type we see during the winter season is snow. But, there are three other types of precipitation we generally get in winter: rain, sleet, and freezing rain. Each type develops when layers of air above have a different temperature than what we see at the surface.

SNOW
Snow is our most common precipitation type of precipitation during winter. Precipitation begins as snow and, if it doesn’t encounter any layers of air that are above freezing (32°F or 0°C) before reaching the ground, it will fall to the surface in the form of snow. Basically, we experience snowfall when the entire column of air overhead is at or below freezing.

SLEET
Many folks confuse sleet and freezing rain. Sleet occurs when snow falls through a shallow layer of warm, above freezing air and melts. The melted liquid drop then encounters another layer of freezing air before reaching the surface and refreezes forming a pellet of ice. When sleet hits a hard surface like your windshield or your deck it will bounce.

FREEZING RAIN
Of all of the winter precipitation types we encounter, freezing rain is the most dangerous and can cause the most damage and headaches. Freezing rain forms when a deep layer of warm air exists above the surface and the surface is below freezing. When this condition occurs, liquid rain can freeze on contact with the cold surface forming a thin layer of ice. Ice can also form on power lines and tree branches causing them to break under the added weight.

GRAUPEL
Graupel is another form of frozen precipitation we sometimes see early in the cold season. Graupel is basically snow pellets. While graupel falls as a pellet it’s white color makes it appear different from sleet – which is clear. Graupel forms when a snowflake partially melts before refreezing into a pellet. Like sleet, graupel bounces when it strikes a hard surface.

RAIN
A deep layer of warm air at the surface can melt any precipitation that started out as snow. It then remains liquid all the way to the surface falling as cold rain. With surface temperatures above freezing, no ice forms and we’re left with just wet surfaces.

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