ROCHESTER, NY (WROC) – Snow is water in its frozen form (ice) that falls through a column of air which is mostly below 32°. It all starts in a cloud, which can contain either all ice crystals, water droplets, supercooled water droplets, or a mixture depending on temperature. We will focus on ice crystals which is nearly synonymous with snow.
To make snow, super cooled water droplets freeze onto some sort of particle (cloud condensation nuclei) like, for example, some dust or exhaust out of a car’s tailpipe. Other water droplets land onto this particle and slowly form an ice crystal that can build out in all directions. The symmetry of a snowflake is explained well by the National Weather service:
The ice crystals that make up snowflakes are symmetrical (or patterned) because they reflect the internal order of the crystal’s water molecules as they arrange themselves in predetermined spaces (known as “crystallization”) to form a six-sided snowflake.
Ice crystals come in many different forms based on a variety of different factors, the main factor being temperature. Different temperatures within the cloud help determine if the ice crystals will form needles, flat plates, stars, or many other different shapes. These shapes can determine how snow will accumulate, what type of snow will fall, and how much the liquid to snow ratio will be.
Here is an example of how a snowflake can form and evolve over time based on the different temperatures and moisture content of the cloud.
There are dozens of different types of snowflakes and we are getting better at capturing them with a camera. Snowflakes can range from stellar dendrites to solid plates to hollow columns to rimed crystals. Each form depending mostly on temperature and humidity. Similar to clouds, it is determined mostly by the observer, but there are guides that show what each should look like. No two snowflakes in the natural world are the same, but this can be done in a lab.