Graupel

Precipitation that forms when supercooled droplets of water freeze on a falling snowflake

Graupel (German: [ˈɡʁaʊpl̩]), also called soft hail, hominy snow, granular snow, snow pellets or popcorn snow, is precipitation that forms when supercooled water droplets in air are collected and freeze on falling snowflakes, forming 2–5 mm (0.08–0.20 in) balls of crisp, opaque rime. Graupel is distinct from hail and ice pellets in both formation and appearance. However, both hail and graupel are common in thunderstorms with cumulonimbus clouds, though graupel also falls in winter storms, and at higher elevations as well.

From Wikipedia, under CC BY-SA. More on occurri.