The windslab problem is likely to develop further with strong to extreme alpine winds in the forecast. With rising temperatures to consider as well, the potential for natural avalanche activity will increase through midday Sunday.
Weather Forecast
A warming trend started today and will continue through Saturday with freezing levels approaching 2000m, NW alpine winds increasing to Strong midday and the potential for light precip. Cooling will start Sunday as alpine winds shift to W and peak in the extreme range early in the day before backing off as the precip ends midday.
Snowpack Summary
10-20cm of snow over the last week over isolated suncrusts and surface hoar. Thin wind slabs can be found in alpine lee areas from strong SW winds on Saturday. Of greatest concern are the weak facets and depth hoar at the base of the snowpack. In thinner snowpack areas with less than 150 cm of snow, triggering a slab on these facets is more likely.
Avalanche Summary
Small windslabs failing off of the crest of the morraines above the iceline trail were seen on a field trip in the Little Yoho region today. The snow safety team at Sunshine Village reported fresh windslabs that had slowly formed over the last few days that were reactive to their ski cuts, one of which propagated 30m .
Confidence
Wind speed and direction is uncertain on Saturday
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.