Heavily rimed new snow, often shaped like little Styrofoam balls.
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 falling graupel is occasionally accompanied lightning as well.
Graupel looks like a pile of ball bearings. Graupel is a common short-lived weak layer in maritime climates but more rare in continental climates. It’s extra tricky because it tends to roll off cliffs and steeper terrain and collect on the gentler terrain at the bottom of cliffs. Climbers and extreme riders sometimes trigger graupel avalanches after they have descended steep terrain (45-60 degrees) and have finally arrived on the gentler slopes below (35-45 degrees)–just when they are starting to relax. Graupel weak layers commonly stabilize in about a day or two after a storm, depending on temperature.