South Coast Inland Avalanche Forecast
Issued: Feb 13th, 2021 4:00PM
The alpine rating is Wind Slabs., the treeline rating is , and the below treeline rating is Known problems include
When wind slabs are the problem, seek out sheltered terrain for the safest, best quality skiing and riding. A shift to south winds will make slab distribution a bit more complex in the coming days.
Saturday night: Cloudy with lingering isolated flurries and a further trace of new snow. Winds becoming light, shifting south then increasing and becoming southwest by morning.
Sunday: Mainly cloudy with isolated flurries and a trace of new snow, increasing a bit overnight. Light to moderate southwest winds increasing over the day and overnight. Alpine high temperatures around -9.
Monday: Cloudy with continuing scattered flurries with a collective 5 to 10 cm of new snow, continuing overnight. Light variable winds. Alpine high temperatures around -6.
Tuesday: Cloudy with continuing scattered flurries bringing up to 5 cm of new snow and 2-day snow totals to 10-20 cm.
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 few more small natural wind slab releases were observed in the north of the region 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. Forecast light new snow amounts and a shift to southwest winds is likely to keep this process going for some time before our supply of loose snow is tapped out. Winds have not been consistent, so don’t be surprised to find reactive slabs on a wide range of aspects as you approach wind-exposed terrain.
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. This surface snow has been progressively 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.
Terrain and Travel
- 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.
Wind slabs at higher elevations could remain reactive to human triggers on Sunday, especially more recent formations and in areas where slabs may have formed over a crust (think solar aspects). Northeast outflow winds may have focused recent slab formation on south through east aspects, but winds are beginning to shift south and we already have reports of new slabs on all aspects.
Increase your caution even more around large, hard wind slabs in alpine areas. these may overlie weak, sugary, faceted snow.
Valid until: Feb 14th, 2021 4:00PM
The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.