Baby Graupel

The area around campus was littered this morning with small, spongy, ball-shaped snow pellets that fell over night.  They are indeed fully recyclable.

Most clouds are comprised of a mixture of ice crystals and supercooled cloud droplets.  Supercooled means that the droplets are below freezing, but remain in the liquid phase.  Graupel is a type of snow pellet that forms as an ice crystal falls and collects these supercooled cloud droplets, which freeze on contact.  This leads to the formation of a ball or lump shaped snow pellet.

Source: Parkerjh, Wikipedia Commons

The snow pellets that fell last night were, however, quite small.  I don't know if there is a minimum size requirement for graupel, so I'll call them "baby graupel."  The formation mechanism was probably similar to that of graupel.  Small ice crystals collected supercooled cloud droplets as they fell.  They just didn't grow to a large size.