Regions
Banff Yoho Kootenay.
Although the danger is rated MODERATE - this means that natural avalanches are not expected, but human triggered avalanches are possible. Possible! Conditions remain tricky despite seeing less avalanches happening. The ones that do happen are huge!
Weather Forecast
Overcast skies and light now forecast for Wednesday with temperatures remaining in the -5 to -10 range as long as the sun doesn't come out, and light winds. This time of year it only takes a short burst of strong sun to have an influence on the snowpack - but right now it looks like Wednesday will be a pretty benign day in the mountains.
Snowpack Summary
Suncrust on the surface in most locations except shaded terrain above 1800m. Shallow snowpack areas remain weak with our focus on facets in the lower snowpack overlain by a stiff slab. Tests on these facets produce easy, sudden collapses. Buried crusts in the upper meter are also a concern, and have been producing avalanches within the past week
Avalanche Summary
Several cornice failures were noted in the Sunshine area. Really important to note the large avalanche in Kananaskis Country that occurred on Sunday - this is now only 48 hours old now, and was a deep, hard slab overlying fist hard depth hoar - sobering. Similar results can be expected in the our region, which is adjacent.
Confidence
Timing or intensity of solar radiation is uncertain
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.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.