Hiding from alpine hazards by tucking into treeline is not always a winning strategy - our persistent slab problem has proven particularly touchy at mid-elevations. This layer is difficult to assess, so choose terrain that won't punish you for an incorrect analysis.
Rider triggerable wind slabs will likely exist on east and north aspects at and above treeline. Recent strong winds may have focused slab formation at lower elevations than is typical.
20 to 70 cm of snow sits over a facet-crust weak layer combination that is possible to human trigger. This problem is particularly concerning in the Duffey Lake area. Recent observations demonstrate the potential for this problem to be triggered remotely and propagate far and wide. It can be found on all aspects at treeline and is most reactive at this elevation band, but it can be found above and below.
Monday night: Cloudy with isolated flurries. Light to moderate west or southwest winds.
Tuesday: Cloudy with isolated flurries. Moderate west or southwest winds. Treeline high temperatures around -2 with freezing levels to 1500 metres.
Wednesday: Sunny. Light to moderate west winds. Treeline high temperatures around +2 with freezing levels rising to 3000 metres.
Thursday: Sunny. Moderate to strong west winds. Treeline high temperatures around _3 with freezing levels remaining near 3000 metres.
On Saturday a fatal avalanche occurred in the Duffey Lake area. This avalanche was a very large (size 3), skier triggered avalanche with significant propagation. It was triggered at upper treeline on a northeast aspect and it failed on a shallower layer of surface hoar before stepping down to the crust from late January discussed in our snowpack summary. A more detailed report can be found here. This layer was also responsible for several large skier triggered avalanches in the neighbouring Sea to Sky region.
Another bout of strong southwest wind over Sunday night may have formed new wind slab on leeward aspects at treeline and above. Slab formation was likely hampered to a degree by already extensive recent wind redistribution as well as the recent formation of surface crusts at lower elevations and on solar aspects.
The primary concern in the snowpack at present is the 20 to 70 cm of snow from the past week that is sitting above a variety of surfaces including facets and crust, but also surface hoar in more sheltered areas at mid-elevations. This layer is most prominent at treeline and above. It has been found on all aspects in the Duffey Lake area.
