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Avalanche Forecast

Archived

Feb 21st, 2016–Feb 22nd, 2016

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kananaskis.

Complex snowpack means making simple terrain choices until these avalanche problems are given some time to resolve themselves.  Cornices are massive at the moment and can easily trigger deeper instabilities causing large and destructive avalanches.

Confidence

High

Weather Forecast

Avalanche Summary

A small to medium cycle was observed today on the Spray Smith Dorrian Highway. Several large avalanches from size 2.5 to size 3 were observed on east through southeast aspects on and below large alpine faces and in some instances running close to the end (3/4 path) of their historical run-outs due to strong to moderate sustained winds yesterday and the week prior. Forecast temperatures and lighter winds will diminish natural avalanche activity.

Snowpack Summary

The snowpack in the alpine has approximately 5cms of low density fluff sitting over wind-pressed and buried wind slabs. On north aspects the bond between the older wind slab interfaces appears to have tightened up in the upper snowpack. The bond at the February 11th melt-freeze & sun-crusts interfaces on southerly aspects has not gained any strength. Recently built wind slabs will also be found at treeline and alpine ridge features on east through south aspects. The cornices high up on alpine ridge top features are immense. Lower elevations at treeline and below will be facetted and lacking structure as a result of shallow heights of snowpack.

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.

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.

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.