Hilberg's Tips -- Winter Precipitation Types 

Do you remember the difference between different types of winter precipitation?  With some parts of our reporting area already seeing snow, we thought it would be a good time for a quick review.

Snow is small white ice crystals formed when supercooled cloud droplets freeze. Snow crystals can have different shapes usually dictated by the temperature at which they form.

Snow pellets, also called graupel, are white, opaque ice particles round or conical in shape. They form when supercooled water collects on ice crystals or snowflakes. They typically bounce when they fall on a hard surface and often break apart.

Snow grains are very small, white opaque particles of ice, more flattened and elongated than snow pellets. Snow grains can be thought of as the solid equivalent of drizzle, or as I like to call it, "snizzle".

Ice pellets, or sleet, are small balls of ice. They form from the freezing of raindrops or the refreezing of melting snowflakes when falling through a below-freezing layer of air near the earth's surface.

For measurement purposes, all four are treated as frozen precipitation, and the snow measurement procedure should be followed.

Freezing rain occurs when rain occurs and the surface temperatures is below freezing. The raindrops become supercooled as they fall through the layer of cold air near the surface and freeze upon impact with surfaces below freezing.  Freezing rain is liquid precipitation and should be measured as you would measure rain, after you have melted the ice in your rain gauge (do not measure any of the ice on the outside of your cylinder). You can report the thickness of ice on surfaces in your observation comments.