Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Banff Yoho Kootenay.
We have seen avalanches failing on the deeper persistent weak layers daily. Although these are generally isolated to thin snowpack areas, the snowpack right now deserves some respect.
Weather Forecast
Cool temps, light winds and convective flurries continue on Wednesday and then a big system is forecasted starting Wednesday overnight and Thursday. Models are showing 20 - 30 cms with moderate to strong SW winds and freezing levels rising to ~ 1900m. The danger ratings will rise rapidly if it materializes.
Snowpack Summary
10-20 cm of new snow over the last couple days, becoming moist below 1700m. Buried sun crusts on solar aspects. Recent West winds have formed soft slabs in lee areas of the alpine. A firm upper snow pack sits over a generally weak mid-pack of facets and depth hoar. In shallow areas snowpack tests results are typically collapses near the ground.
Avalanche Summary
Two size 2 - 2.5 natural avalanches overnight Monday in the Sunshine area. These were on N aspects in the alpine and were triggered by small loads (10-15cms of new snow with light winds). Additionally, a couple recent close calls: Monday a skier accidental size 2.5 on the Collie Glacier and on Sunday a skier accidental size 2.5 near Bow Summit.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Thursday
Problems
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.
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.