Avalanche Forecast

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Friday night: Clear. Moderate to strong southeast winds.

Saturday: Becoming cloudy with isolated flurries bringing a trace to 5 cm new snow, mainly in the south of the region, continuing overnight. Moderate to strong east or southeast winds. Alpine high temperatures around -16.

Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Alpine high temperatures around -11.

Monday: Mainly cloudy with isolated flurries and a trace of new snow. Light west winds. Alpine high temperatures around -8.

Recent wind slab formations are a concern throughout 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. A size 1, remote-triggered wind slab reported on 1950 m north aspect in the McGillivray area on Thursday. It failed on our more recent (Feb 4) surface hoar layer.

A notable size 3 (very large) persistent slab was remotely triggered (from a distance) by a group of skiers in the McGillivray Pass area on 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. Continued easterly winds may keep this process going for some time before our supply of loose snow is tapped out. Winds have not been consistent; one report even mentions loading occurring on northeast slopes, so don’t be surprised to find reactive slabs on a wide range of aspects as you approach the alpine.

The snow surface 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, including older wind slabs that have been gradually losing cohesion and reactivity under prolonged cold temperatures. 

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. No persistent weak layers are currently considered problematic in the Coquihalla.

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.