A combination of strong to extreme winds and new snow will likely increase the sensitivity of wind slabs and initiate loose dry avalanche in steep terrain.
Last week's snow and winds have created wind slabs in the alpine. As strong to extreme winds and new continue through Sunday, we expect natural activity in the alpine and slab development at treeline.
The Dec. 2 crust/facet layer down 50-70cm has not presented as a widespread problem, but a skier triggered avalanche in Kootenay Thursday shows it has started to wake up. We are concerned with the potential for further slab development this weekend.
A long period of cold has lead to faceting of the upper snowpack. This weak snow will be more sensitive to triggering and will also allow avalanches to run further and faster. We expect the wind to generate a significant amount of loose dry activity.
As the BC low moves into Alberta, strong to extreme winds will dominate through the forecast region. By Saturday night we will begin to see snow fall, forecasted accumulation amount very from 10 to 25cm by Monday. Thankfully temperatures will continue to climb through till Monday with valley bottom highs near -10.
Strong winds are transporting faceted surface snow at upper elevations, forming hard slabs on lee slopes. There is 50-70cm over the Dec 2 crust/facet combo which exists below 2200m and appears to be waking up as a persistent weak layer. Shallow areas (<100cm) have weaker basal facets which also present cause for concern as temperatures rise.
There was a skier triggered size 2 avalanche in Kootenay NP Thursday. This appears to have been on the Dec. 2nd crust/facets. A few other avalanche obs in Kootenay appear to have released on the same interface. Strong winds today have likely increase the natural avalanche activity at upper elevations.
