LEXICON: slope aspect

A slope's aspect or orientation relative to points of the compass (e.g. north facing) or the wind (e.g. downwind). This is a critical factor in assessing avalanche probability. For example, north facing slopes tend to be more avalanche prone in winter but by the spring south facing slopes may present the greater hazard.

Why so?

In general terms this is because north facing slopes receive less sun in winter to melt and condense the snowpack. These shady slopes not only hold the best powder we all crave but are also prone to unstable layers of ‘depth hoar’ that significantly increase the risk of avalanche. However, by the spring south facing slopes may become over-exposed to sunshine leading to dangerous wet snow slides.

The orientation of a slope with respect to wind is another primary factor in avalanche formation. Wind distributes snow unevenly and, during storms, will pick up loose snow and transport it from one slope to another. Unstable wind slabs often form on downwind (lee) slopes following a storm and are liable to release as slab avalanches."