Avalanche Forecast

Archived

Feb 15th, 2015–Feb 16th, 2015

Alpine

Natural avalanches possible, human triggered probable.

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis.

The SPAW issued by Kananaskis and the National parks has now been extended to Tuesday. See www.albertaparks.ca or here for details.

Confidence

Good

Weather Forecast

Temperatures will be cooling over the next few days to more seasonal values. Freezing levels will remain at lower elevation until wednesday when they are again forecast to climb up to 1800m. The sun is gonna be in and out over the next while and it seemd to pack a punch in terms of solar radiation so keep an eye on overhead slopes that may be in the sun.

Avalanche Summary

A skier accidental sz 2.5 avalanche occurred late in the day on Saturday. The slide occurred on an E aspect at 2400m, was 130m wide, up to 100cm deep and ran over 600m. 5 skiers were involved and one fatality resulted. Yesterday several sz 2-3 avalanches were observed when the sun came out. Some of the fracture lines were over 500m wide failing at what appeared to be the jan 31st interface down 50-90cm and some avalanches also stepped down to ground.

Snowpack Summary

A temperature crust from the recent heat can be found on all aspects up to 2200m then only on solar aspects up to 2400m. Easy to moderate sheers persist within the upper snowpack down 30-40cm. Extended column tests also indicate that this layer is prone to wide propagations. The Jan 31st interface is down 70-80cm but the bond at this interface seems to be improving. The basal layers in the snowpack area still weak and any avalanche that is triggerred will likely step down to these basal layers. Temperatures are cooling and freezing the previous isothermal snowpack at lower elevations.

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.

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.