Ice pellets are a form of precipitation. They are small, translucent or clear balls of ice. Ice pellets are rain drops that have frozen before they hit the ground. When they hit the ground, they bounce. Ice pellets are also called sleet and can be accompanied by freezing rain.
In winter, precipitation usually begins falling out of a cloud as ice particles. If the temperature underneath a cloud stays below freezing all the way to the ground, the ice crystals never melt and snow falls. If the temperature is above freezing below the cloud bottom to the ground, the frozen particles melt into liquid droplets that reach the surface and this is called rain.
Ice storms occur when precipitation particles melt and then fall through a layer of cold air near the ground. Sleet results when the layer of subfreezing air at the surface extends upward far enough so that raindrop freezes into a little ball of ice. Freezing rain forms when a very shallow layer of cold air at the surface causes freshly melted raindrops to freeze on contact with exposed objects on the ground, whose temperature is below freezing.
Another type of precipitation is graupel. Ice crystals may encounter small drops of water whose temperatures are below freezing. These supercooled liquid droplets freeze when they come into contact with the snow crystal. When this process continues so that the shape of the original snow crystal is no longer identifiable, the resulting ice particle is called graupel. Graupel is brittle and will fall apart when it strikes the ground.
On Sunday afternoon, Jan. 27, Madison experienced rain, freezing rain, sleet and snowfall all in one day.