Avalanche Forecast

Archived

Feb 22nd, 2015–Feb 23rd, 2015

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Kananaskis.

There is still good skiing to be had on sheltered polar aspects. Watch out for reverse loaded slopes and keep an eye out for rising temps. PW

Confidence

Good

Weather Forecast

Tomorrow will see a mix of sun and cloud, but will be warming to near zero in the alpine. Freezing levels are expected to climb to 2200m. The winds will be light from the north.

Avalanche Summary

There were numerous skier initiated sluffs in steep(>40) terrain, but the sluffs were not running far and slowed to where the angle eased to 35deg. or less.

Snowpack Summary

The storm snow has settled dramatically on southern aspects due to solar effect, but up to 12cm of low density snow remains on the surface on polar aspects. There has been evidence of reverse loading wind effect at upper exposed treeline and alpine elevations and soft slabs have formed in the immediate lees of features at these elevations. A test pit today at treeline elevations showed the upper snowpack to be healing and gaining strength. The pit was in a sheltered area, but exposed areas at this elevation have seen some wind. The mid-pack is gaining strength but weak facetted grains still dominate the base of the snowpack. At 2400m there is a discernable crust on solar aspects and 2100m and below there is a crust on all aspects under the most recent snow.

Problems

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.

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.