Definition: Graupel forms when snow in the atmosphere encounters supercooled water. In a process known as accretion, ice crystals form instantly on the outside of the snow and accumulate until the original snowflake is no longer visible or distinguishable.
The coating of these ice crystals on the outside of the snow is called a rime coating. The size of graupel is typically under 5 millimeters, but some graupel can be the size of a quarter (coin).
To tell the difference between graupel and hail, you simply have to touch a graupel ball. Graupel pellets typically fall apart when touched or when they hit the ground. Hail is formed when layers of ice accumulate and are very hard as a result.
Also Known As: snow pellets, soft hail, small hail, tapioca snow, rimed snow, ice balls