Graupel, otherwise known as snow pellets, is snow that falls but then supercooled water droplets form around it. This makes it look like mini Styrofoam balls. They usually have a white hue to them.
Supercooled water is water below our freezing mark of 32 degrees. Graupel is often confused for hail but they are made differently in our atmosphere.
For Graupel to form, you need cloud temperatures to be below the freezing mark of 32 degrees and surface temperatures to be below 45 degrees.
To learn more about different types of precipitation, click here.