Beyond The Forecast: The difference between graupel and sleet.

Sleet also, referred to as ice pellets, is a precipitation type consisting of grains of ice that form when raindrops or partially-melted snowflakes fall through a layer of subfreezing air and freeze solid before they reach the ground. Graupel, is formed differently. Water droplets in clouds exist in a supercooled state they are the ones whose temperature is below freezing. If snowflakes originate in the clouds above that level descend through a layer of supercooled droplets, they frost over, and the result is graupel white and easily crushed pellets.