Avalanche Forecast

Moderate - Wind effect is extremely variable

Some cloud Wednesday then mostly clear and cold until light snow arrives on Friday. Overnight lows near -25 Celsius in some locations. WEDNESDAY: Cloudy with isolated flurries possible. Tree line temperatures around -14 Celsius. Winds moderate westerly 20-30 Km/hr.THURSDAY: Sunny with cloudy periods. Tree line temperature around -11 Celsius. Winds light westerly becoming moderate 40 Km/hr.FRIDAY:  Light snow (5-10cm). Tree line temperature around -10 Celsius. Moderate southwest winds 30-50 Km/hr.

On Sunday, natural wind slab activity to size 3 was reported on south / east aspects from 1250m right up to 2400m elevation. See this MIN post for a good example of these avalanches. See also this MIN post for dramatic photos of wind effect. On Saturday we received reports of a large avalanche running on a deeply buried weak layer with 1.5m crown and good propagation. This feature was steep open terrain below tree line on an east facing aspect. On Thursday we received reports of recent cornice-triggered slab avalanches on high lee (down wind) features in the alpine. See this MIN post for more information. Previously, a very large, widespread natural avalanche cycle up to size 4 was observed around February 10th. Slopes of all aspects and elevations ran full path and reached valley floor. In some cases, mature timber was destroyed. Many of these failed on persistent weak layers mentioned in the snowpack discussion. Although natural avalanche activity on these layers has tapered-off, human triggering of very large avalanches remains a very real possibility.

25-40cm of storm snow from last week is settling into a slab in the upper snowpack. Winds have been strong from the north west through south west, creating reactive hard wind slabs (10-15 cm thick) in exposed locations on down wind features. See here for a good video summarizing conditions near Valemount. These accumulations overlie a mix of older wind slabs in exposed higher elevation terrain, a sun crust on steep solar aspects and surface hoar on sheltered slopes.Below the snow surface, several persistent weak layers make up a troublesome snowpack. In the top 1-1.5 m of the snowpack, two surface hoar layers buried in January can be found. Expect to find at least one of these layers on all aspects and elevations.Deeper in the snowpack (120-200 cm deep) is a facet/crust/surface hoar layer from December, most prevalent at and below tree line.Near the base of the snowpack is a crust/facet combo, most likely to be triggered from thin spots in the alpine.All of these layers have produced large avalanches recently. The wide distribution and ongoing reactivity of these layers suggests that avoidance through choosing simple terrain is the best strategy.