Snow Formation and Avalanches : Page 188

Effect of wind on texture.—The effect of wind on fallen snow is varied and difficult to predict accurately. The primary effect of a dry wind is evaporation of the snow. A humid, or wet wind nearly always causes packing of the surface snow (assuming that the snow is not already hard-packed), and simultaneously causes erosion (wind-cut snow) and drifting. Wind packing sometimes forms a crust which is well bonded to the underlying snow; however, if there is simultaneous deposition of fresh or drifting snow, a wind slab is apt to form. This is poorly bonded to the underlying snow, and may break up when disturbed, sliding away in blocks. Therefore, wind slabs are likely to be on lee slopes; a wind-cut surface is usually a safe crust and not a slab. Frequently, soft snow under a wind slab will settle unevenly, leaving spaces under the slab. Owing to the lack of continuous support the slab breaks easily under the weight of a skier.