New snow is expected to bond poorly to the underlying surface and form fresh reactive wind slabs in lee areas. What won't be as evident underfoot is the buried hard slabs from this week's northerly winds. Both of these problems are most likely to be an issue in wind-exposed alpine and treeline terrain.
Triggering a deep persistent slab remains possible, especially in areas with a thin snowpack. Sheltered terrain will offer the best and safest riding.
Up to 20 cm of new will accumulate in the overnight period. The accompanying southwest winds may create fresh wind slabs in lee areas.
Keep in mind that older, stiff wind slabs from previous northerly winds may still be reactive to human-triggering and are now hidden under the fresh storm snow.
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.
On Thursday, two size 3 deep persistent slab avalanches were observed just north of the Hurley summit. These slabs are suspected of having failed within the last two days. One was on a north-facing alpine face and the other an exposed, east-facing open slope at treeline. A nearby operation was able to trigger two size 2 wind slabs with a snowcat groomer on northwest-facing terrain at treeline. Skiers were able to trigger small (size 1) wind slabs in alpine terrain on south-to-east aspects in the Birkenhead north of Pemberton.
On 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.
Looking forward to Sunday, fresh and reactive wind slabs are expected to form in lee areas. Keep in mind that older, stiff wind slabs may now be hidden under the storm snow.
For a deeper dive into this week's conditions, check out this awesome South Coast Conditions Report posted by Zenith Guides.
Saturday night's storm will accumulate 10-25 cm of new snow down to valley bottom. This new snow is expected to bond poorly to the stiff wind slabs and near-surface facetting 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.
Saturday night
Cloudy with snowfall, 5-15 cm of accumulation. Alpine temperatures drop to a low of -10 °C. Light ridge wind from the southwest gusting to 45 km/h. Freezing level at valley bottom.
Sunday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Light ridge wind from the southwest. Freezing level at valley bottom.
Monday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -8 °C. Light ridge wind from the southwest. Freezing level at valley bottom.
Tuesday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -8 °C. Ridge wind light from the southwest. Freezing level at valley bottom.
More details can be found in the Mountain Weather Forecast.
