Drifting snow adding weight onto leeward terrain. A sign of instability.
Wind transport of snow is an effective way to load a slope. Wind erodes snow from windward features and deposits it into thicker drifts on the downwind side of ridges, gullies, or convexities. These thick drifts quickly add stress to the snowpack on the leeward slope. Winds often deposit snow 3 to 5 times faster than snow falling from the sky. Furthermore, winds break down snow flakes into smaller, more compact grains which form denser, more cohesive slabs. Wind loading is optimized when there is new or recent snow available for transport and moderate to strong winds. Blowing snow and fresh drifts are indications of active or recent wind loading, and thus, an increase in avalanche concerns on wind loaded slopes.