GRAUPEL

Recently, on a Columbus weather report, the meteorologist described graupel as "the wintry precipitation term you've never heard of" and told that it is also known as "soft hail" and "snow pellets".

Although I have seen graupel, it is indeed a new word for me. The National Weather Service (see chart below) defines graupel as "small pellets of ice created when super-cooled water droplets coat (or rime), a snowflake".  Graupel pellets are cloudy or white, not clear like sleet.