5.2.2 Wind

New event: Wind

Six days after the initial snowfall, a 15-m/s (30-kt) wind event occurs, which lasts twelve hours.

In general, wind can significantly redistribute snowpack in the mountains where high wind speeds are common. With wind speeds of 15 m/s, snow depths can be at least 50% higher in redistributed areas. The depth is typically greatest on the lee or downwind side of a ridgeline. The location of the maximum is typically dependent on the wind speed, with higher speeds usually corresponding to distances further downwind from the crest.

Snow distribution at the conclusion of the wind event.

When wind redistribution occurs relatively quickly (on the order of several hours), it produces stress that a formerly stable snowpack may not be able to resist. The quickly added weight may lead to an avalanche.

Redistributed snow is inherently of higher density than undisturbed snow. When it accumulates on low-density snowpack, it forms a slab. The slab increases the weight of the snowpack, to the point where it may exceed the counteracting force of friction. When this occurs, the slab can fail, causing an avalanche.

If subsequent snowfall covers redistributed snow, high-density layers will be created within the pack.

Wind scouring snow off of the windward side of the peak and depositing it on the leeward side. (Photograph courtesy of Richard Armstrong.)