snowformation

Snow formation is the meteorological process by which atmospheric water vapor transitions into solid ice crystals within clouds and subsequently falls to Earth's surface as snowflakes. This process occurs most readily in cold clouds where the temperature is at or below freezing and there is sufficient moisture.

In many clouds, ice crystals grow through deposition, while surrounding supercooled liquid droplets may freeze onto them. The Bergeron process explains why snow forms in such mixed-phase clouds: the vapor pressure over ice is lower than over liquid water at the same subfreezing temperature, so water vapor tends to deposit onto existing ice crystals, allowing them to grow while liquid droplets evaporate.

Crystal shapes depend on ambient temperature and humidity. Snow crystals can take forms such as hexagonal plates, columns, needles, or complex dendritic structures. As they grow, crystals may collide and stick together, producing aggregates that become larger and appear as characteristic snowflakes. During their descent, crystals pass through layers of varying temperature; some portions may melt, leading to wet snow or slush at the surface, while in colder, drier air the snow can be light and fluffy.

Snow formation has practical implications for weather prediction, the seasonal snowpack, water resources, and transportation. Snowfalls influence albedo and energy balance, affect soil moisture recharge, and require management for roads and aviation. Snow is distinct from related phenomena such as frost, sleet, freezing rain, and hail, which arise from different atmospheric pathways or phase changes.