New snow and strong southwest wind may build fresh and reactive wind slabs. Take a cautious approach and investigate the bond between the new snow and the old surface before committing to your line. Keep in mind that if triggered, wind slabs may step down to the deep persistent slab problem resulting in large avalanches.
New snow accompanied by strong southwest wind on Thursday may build fresh wind slabs on lee slopes. Wind earlier this week combined with last weekend's storm snow has varied in direction so watch for wind slabs on all aspects.
Wind slab reactivity may persist for longer than is typical due to the weak surface they are sitting on.
A layer of weak facets sits near the base of the snowpack. This layer is most likely to be problematic in steep, unsupported, wind-loaded terrain in the northern part of the region around the Chilcotins, Birkenhead, and Hurley.
No new observations were reported Tuesday.
On Monday, loose dry sluffing from steep terrain was seen as well as a remotely triggered wind slab avalanche size 1.5 that reportedly failed on facets below the recent storm snow.
Last Thursday, two size 3 deep persistent slab avalanches were observed just north of the Hurley summit. One was on a north-facing alpine face and the other an exposed, east-facing open slope at treeline.
Last Friday, two large (size 3-4) natural deep persistent slabs were observed on south and southeast alpine faces in the Birkenhead. We suspect these slabs occurred as a result of wind-loaded from strong northwesterly winds.
Up to 20 cm of new snow should accumulate across the region by Thursday afternoon. This will add to last weekend's storm that brought 15-30 cm of storm snow. In some areas, this new snow has bonded poorly to the stiff wind slabs and near-surface faceting formed by recent wind and cold temperatures.
A melt-freeze crust from late January can be found down 60-80 cm. At the moment this layer appears to be gaining strength though in isolated areas small facets can still be found above the crust.
There is a widespread weak layer of large sugary facets at the bottom of the snowpack. Recent avalanche activity on this layer has been confined to northern parts of the region in the Chilcotins. Snowpack depths around treeline range between 150 to 250 cm.
Wednesday Night
New snow 10-15 cm. Alpine temperatures -10°C. Ridge wind southwest 35 to 65 km/h. Freezing level valley bottom.
Thursday
Snow 5 cm. Alpine temperatures -8 °C. Southwest wind 30 to 70 km/h. Freezing level valley bottom.
Friday
Cloudy with sunny periods and a trace of snow. Ridgetop wind 25 to 55 km/h from the southwest. Alpine temperatures -9°C. Freezing level valley bottom.
Saturday
A mix of sun and cloud with isolated flurries. Alpine temperatures near -7°C. Ridge wind northeast 15 km/h. Freezing level valley bottom.
More details can be found in the Mountain Weather Forecast.
