»graupel

The Utah Avalanche Center's online dictionary provides this definition for graupel:

Graupel is that Styrofoam ball type of snow that stings your face when it falls from the sky. It forms from strong convective activity within a storm (upward vertical motion) caused by the passage of a cold front or springtime convective showers. The static buildup from all these falling graupel pellets sometimes cause lightning as well.

Graupel may come from German, but I do not know whence.