snow crystal

Graupel, also known as snow pellets or soft hail, forms when water droplets freeze onto a snow crystal, according to the National Weather Service.

If the riming is particularly intense, the rimed snow crystal can grow to an appreciable size, but remain less than 0.2 inches.

Powdery snow, the kind you can clear with a leaf blower, forms when critically thick air layers aloft are saturated enough and cold enough for highly efficient snow crystal growth.

“It takes maybe 100,000 water droplets evaporating to make one snow crystal,” Dr. Libbrecht said.

It's true that no snow crystal — the technical term for a single snowflake — is the same, and that's because of the complex processes that turn an ice crystal into a unique, symmetrical shape.