Avalanche control along the Icefields Parkway produced results up to size 3. The recent storm snow is stressing the snowpack and will require some time to stabilize, choose simple terrain that is well supported.
Weather Forecast
Periods of light snow with accumulations up to 2cm by Monday evening. Winds are forecasted to be light from the Southwest with temps ranging from -10 to -16.
Snowpack Summary
40cm of settling HST in the last 2 days came in under the influence of mostly light, with some moderate southerly winds. Soft slab forming at treeline and above. The mid and lower snowpack is structurally weak, the base of which is large (5mm) depth hoar crystals and a deteriorating rain crust.
Avalanche Summary
Avalanche control work produced results up to sz 3, some of which stepped down to deep persistent layers or to the ground where weak facets and depth hoar exist. Natural activity was most prevalent in the alpine and similar to the control work, was stepping down, resulting in deep releases, sz 2-3.
Confidence
Due to the number and quality of field observations on Sunday
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.
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.
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.