Continually assess the bond between new snow and the old surface. Be extra cautious in wind-loaded terrain.
Do not underestimate the influence of the sun on a cold, clear day. Avalanche danger could increase rapidly on sun-exposed slopes when solar radiation is strong.
Cornices may have grown significantly with wind and snowfall over the past 3 days. Be especially mindful of overhead cornice hazard if the sun comes out and the storm snow is experiencing strong solar radiation for the first time.
A weak layer formed in late January may be found 50 to 150 cm deep in the snowpack. This layer consists of faceted snow, a sun crust on steep solar aspect, and most notably large surface hoar crystals in sheltered terrain.
Reactivity on this layer has tapered, but a significant amount of new load may cause this layer to 'wake up'.
The most reactivity on this layer has been seen between 1600-2200 m in open areas in the trees, in cut blocks, and on steep convexities. Terrain features to be suspect of include the lee side of ridges, openings in trees, cut blocks, and burns, especially on northerly aspects where the layer may not be capped by a firm crust.
This weekend's storm brought 30-100 cm of storm snow which overlies the February 15th drought layer.
Cold temperatures may decrease the reactivity of the more widespread storm slab problem, but deeper, and stiffer slabs will exist in wind-loaded terrain, which probably remain reactive to human-triggering.
Do not underestimate the influence of solar radiation on these cold days! Reactivity could increase rapidly on sun-exposed slopes when solar radiation is strong.
Bundle up in your warmest gear, arctic air is here!
Sunday Overnight: Cloudy with light flurries, clearing into the morning. Light to moderate northerly winds. Alpine temperatures plummet to around -20 C.
Monday: Mainly clear and cold. Light northerly winds. Alpine temperatures around -25 C.
Tuesday: Cold and clear. Light northerly winds. Alpine temperatures around -20 C.
Wednesday: Cloudy with light flurries. Light to moderate northwesterly winds. Alpine temperatures around -16 C.
During the peak of the storm on Saturday, numerous natural and human-triggered storm slabs were reported on all aspects due to rapid loading. Larger natural and human-triggered wind slab avalanches were reported in wind-loaded terrain in the alpine and treeline. Several natural dry loose avalanches were reported out of steep terrain on all aspects.
Explosive control last week initiated some larger persistent slabs up to size 3.
This weekend's storm brought 20-70 cm of new snow above 1400 m. At lower elevations, a surface crust can be expected from wet snow/rain throughout the storm. Up to 120 cm now overlies the old, hard surface, which is a result of a period of high pressure in mid-February. The layer is comprised of facetted snow, a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline.
The mid-January surface hoar/crust layer is now down 50-150 cm in the snowpack. This layer has not been reactive to skier traffic in the past week and is showing limited reactivity in snowpack tests. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche stepping down to this layer.
The facet/crust layer that formed in early December is now buried around 150 to 250 cm. Human triggering of this layer is unlikely, except perhaps on a re-loaded bed surface or in a shallow snowpack area. This layer may become a concern during periods of warming or heavy loading.
