Avalanche Forecast

High -

Saturday night: Decreasing cloud with isolated flurries and a trace of new snow. Strong northwest winds easing to moderate by morning.Sunday: Cloudy with sunny periods. Light to moderate northeast winds easing over the day. Alpine high temperatures around -12.Monday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures around -13.Tuesday: Cloudy with scattered flurries bringing a trace to 5 cm of new snow. Light southwest winds. Alpine high temperatures rising to -4 as an alpine temperature inversion layer establishes toward evening.

Although we don't yet have reports of avalanche activity from Saturday in the Cariboos, preliminary observations from neighbouring regions show a spike in natural and human triggered storm slabs on a wide range of aspects and elevations. With some of the deepest accumulations of the BC interior reported in our region, it's reasonable to assume it was an active day for avalanches, whether natural or human-triggered.Prior to the storm, a few large (size 2-3) natural persistent slab avalanches were reported last Sunday. These avalanches were reported on south aspects in the alpine. Last week numerous persistent slab avalanches (up to size 3) were reported on all aspects (a few that even destroyed mature trees). The persistent slabs were 50-150 cm thick and likely failed on the early December weak layer. Looking forward, expect diminishing snowfall and wind to decrease natural avalanche activity while the potential for human triggering remains elevated. Although the likelihood of storm slabs 'stepping down' to deeper persistent slab problems is in question, travel plans should account for very large avalanches as the possible result.

Saturday's storm left about 30-40 cm of new snow on the surface in the region. Below the new snow, a new layer of surface hoar was recently observed growing on the previous snow surface at treeline and above. This weak interface covers a few cm of older low density snow from a few days ago, which itself sits above a layer of wind affected snow in the alpine and around treeline.A weak layer that formed during the dry spell in early December is now 110-180 cm deep. The layer is composed of weak facets, surface hoar, and a sun crust on steep south-facing slopes. Although activity at this layer has greatly diminished over the last week, it remains a concern for the possibility of surface slabs acting as a trigger for 'step down' avalanches. The places of greatest concern for this type of avalanche will be north and east facing slopes between 1900-2300 m and steep south-facing slopes in the alpine.A weak layer from mid-November and a crust that formed in late October are found near the bottom of the snowpack. The probability of triggering these deeper layers is low, but the most suspect areas would be shallow spots in steep rocky terrain.