Snow

Snow changes properties and is difficult to measure and study in its natural environment. Ice Crystals form when water vapor condenses around and freezes upon a foreign particle such as dust or sea salt. These Ice crystals then form various varieties of snow flakes.
Snowflakes can fall in many forms, including ferns, crystals and needles.

these picture from here

These snow flakes begin transforming as soon as they hit the ground. They begin to morph in a combination of melting, freezing, evaporation and sublimation*. They become needles, columns, and finally simple round pellets.

these picture from here

* Sublimation is when ice evaporates directly instead of melting first to water and then evaporating.

These pellets the bond again through a process of melting, freezing, evaporation and sublimation at their contact points, this creates a strong snow pack.

image from Physics of Skiing

To learn more about snow and how it creates a snow pack on a skirun, click here.

To see some neat pictures of snowflakes and learn about creating artificial snowflakes click here.