The term basal facets refers to faceted snow found at the base of the snowpack. Basal facets are a common feature of thin snowpack areas exposed to prolonged cold temperatures. These conditions create a strong temperature gradient that encourages the faceting process in the lower snowpack.
Once formed, basal facets tend to persist for some time (frequently the whole season), they usually act as a persistent weak layer, and are often associated with deep persistent slab avalanche problems.