Graupel are snowflakes covered in rime ice. They're like big styrofoam snowflakes, and because they form in warmer air, they melt almost immediately on contact with anything solid. Yesterday the Chicago Tribune had a handy explainer on the back page, just in case people were curious what was hitting them on the head standing on "temporary" railway platforms this morning. (Fuck Bruce Rauner and his entire party.)
Sorry. I get a little grumpy when I wake up on May Day to mid-March weather. With graupel.