Avalanche Forecast

Sunday night: Mainly cloudy with isolated flurries and a trace of new snow, increasing a bit by morning. Light to moderate southwest winds.

Monday: Cloudy with continuing scattered flurries with 5 to 10 cm of new snow, including the overnight period., Light flurries continuing overnight. Light southwest winds shifting northwest over the day and increasing overnight. Alpine high temperatures around -7.

Tuesday: Cloudy with continuing scattered flurries bringing up to 5 cm of new snow and 2-day snow totals to 10-15 cm, continuing overnight. Light to moderate southwest or west winds. Alpine high temperatures around -8

Wednesday: Diminishing cloud and isolated flurries with another up to 5 cm of new snow from the overnight period. Light west or northwest winds. Alpine high temperatures around -10.

Recent wind slab formations are widespread in the region, with small (size 1.5) wind slabs able to be triggered with ski cutting on steep leeward and crossloaded slopes in the Coquihalla on Friday and Saturday. Check out this MIN report for a great example of layered/obscured wind slabs reactive to skier triggering in the south of the region. Another MIN detailing an avalanche involvement in the north of the region gives a clear picture of hazards perched on alpine features.

A notable size 3 (very large) persistent slab was remotely triggered (from a distance) by a group of skiers in the McGillivray Pass area last Monday. This occurred on a southwest aspect at 2400 metres. It was described as a hard wind slab formed over our facet layer from late January.

Region-wide, recent northeast winds formed many new wind slabs across exposed higher elevation terrain. Forecast light new snow amounts and a shift to southwest winds will likely keep new slab formation going for some time. Winds have not been consistent, so don’t be surprised to find reactive, potentially layered or buried slabs on a wide range of aspects as you approach wind-exposed terrain.

The surface now being flurried on is otherwise composed of a wide-ranging 20 cm (north of the region) to 60 cm (south of the region) of low density snow in shaded, sheltered areas (now likely a bit more scarce), along with more widespread wind-affected surfaces. This surface snow has recently been changing into weak, faceted grains.

On solar aspects, a thin recent sun crust may be found on or right near the surface or beneath recently wind transported snow, potentially contributing to the reactivity of new slabs on sun-exposed aspects.

Persistent weak layers of concern below this storm snow vary by location in the region. In the south, the primary feature, found at treeline and below in the Allison Pass area, is a melt-freeze crust from mid-January, about 50 cm deep. Although this layer is present (twice as deep) in the Coquihalla snowpack, no persistent weak layers are currently considered problematic in that area.

In the north, many of the recent wind slab formations discussed above have been reactive to skier triggering on early February interfaces of surface hoar (think shaded aspects), and may also exist over a thin sun crust from the same period (think solar aspects). Another older (January 24), slightly deeper, widespread layer of faceted snow remains a concern in shallow or variable snowpack depth locations in the alpine. 

Also In the north, a melt-freeze crust from early December may be found 100 to 200 cm deep. Recent reports have suggested that this layer is unreactive and gaining strength, however ongoing cold temperatures may currently be weakening the snow around it in thin snowpack areas.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Watch for areas of hard wind slab on alpine features.
• Be aware of highly variable recent wind loading patterns.