If you've never heard of it, it's OK. This type of precipitation doesn't happen too often, especially in Southern California.
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So what is graupel?
Graupel are soft, small pellets formed when supercooled water droplets - typically at a temperature below 32F - freeze onto a snow crystal, according to the NOAA.
For example, in the colder parts of a cloud where the temperature is, let's say, in the upper 20s, there are small snowflakes.
In the portion of the cloud where temperatures are very close to freezing - or slightly below freezing - little pieces of ice gather around the snowflake and freeze.
Then that becomes graupel.
Graupel is also called "snow pellets" or "soft hail," as the graupel particles are fragile and generally disintegrate when handled, the NOAA says.
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While we're at it, here's a look at what makes hail.
Hail is frozen precipitation that can grow to very large sizes - sometimes even the size of golf balls! Fun fact: According to the NOAA, the largest hailstone recovered in the United States fell in Vivian, South Dakota, on June 23, 2010, with a diameter of 8 inches and a circumference of 18.62 inches. It weighed 1 lb 15 oz.
It forms in strong upward winds in thunderstorms then fall before melting.
Hail's texture is pretty hard and solid so if the winds are strong enough, it can fall at an angle or even nearly sideways! Officials say wind-driven hail can tear up siding on houses, break windows and blow into houses.
Lastly, there's snow. This is when you have cold, freezing air from the cloud to the surface. This allows the ice crystals to stay as ice crystals all the way down to the ground.