Recently formed storm slabs are expected to be reactive to human-triggering on Sunday. Conservative terrain selection is critical and it is best to avoid recently wind loaded areas. If the sun comes out, use extra caution on steep south aspects.
Weather Forecast
Unsettled conditions are expected on Sunday as cold Arctic air begins to move south and replace the recent storm system. Lingering flurries are expected in the morning and sunny breaks in the afternoon. Alpine winds are forecast to be light to moderate from the northwest and freezing levels are expected to fall below valley bottom. On Monday, mostly sunny conditions are expected with light alpine winds from the northwest and treeline temperatures below -10C. On Tuesday, a mix of sun and cloud is forecast with light alpine winds from the northwest and treeline temperatures below -15C.
Avalanche Summary
No new avalanches have been reported in this region recently but this is most likely due to a lack of observers. We expect avalanche activity to increase throughout the weekend with the ongoing storm. If you are out in the mountains, please post your observations to the Mountain Information Network (MIN).
Snowpack Summary
Observations are very limited in this region. The new snow and wind on Friday and Saturday are expected to have created new storm slabs in the alpine and open areas at treeline. The mid-November crust is down around 100 cm. This layer may become more reactive if facets form on the crust and the snow load increases. Below the crust the snowpack is generally well settled. Average snowpack depths at treeline are 140-200 cm with generally less snow in the northern parts of the region. Watch out for stumps, rocks, and open creeks below treeline.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.