Powder snow is a type of freshly fallen snow characterised by its lightness, dryness, and low density (30-70 kg/m³, compared to 200-500 kg/m³ for wet snow). Its crystals retain their intact hexagonal branching structure (dendrites), with large amounts of air trapped between them, making it the most prized snow type for skiing and snowboarding.
Formation conditions
It forms when the air temperature is significantly below 0 °C (ideally -10 °C or lower) and humidity is relatively low. Under these conditions, snow crystals grow large and branched, and upon landing they do not compact because there is no liquid water acting as "glue". The absence of partial melting during the fall preserves the fluffy structure.
In Spain, powder snow is common in the Pyrenees (especially on the northern slopes and above 2,000 m), in Picos de Europa during Arctic intrusions, and occasionally in Sierra Nevada with northerly snowfalls. The difference from wet snow (which falls near 0 °C and compacts easily) is fundamental for ski resorts.
Powder snow is also an excellent thermal insulator (protecting the ground from extreme frost) and contributes to the water storage of mountain snowpacks, crucial for spring and summer water supply. However, layers of powder snow over ice crusts are a significant risk factor for slab avalanches. See also: graupel, frost.