Frozen precipitation in the form of individual ice crystals or aggregates of ice crystals. Graupel (also called snow grains) occur in the same conditions that produce snow, which is why we include them under snow. Graupel/snow grains occur where there is an overabundance of supercooled liquid water droplets. These supercooled liquid droplets freeze upon contact with a snowflake (a process called riming) and form the small particles that you sometimes seen.