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Avalanche Forecast

Archived

Feb 4th, 2014–Feb 5th, 2014

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

Regions

Purcells.

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Confidence

Fair - Wind effect is extremely variable

Weather Forecast

Synopsis:  A very strong ridge of high pressure continues to dominate the weather pattern.  In the extended period the models are not breaking down the ridge as quickly, so it looks like Saturday will be dry throughout the province.Wednesday: Sky: Clear; Freezing Level: Valley Bottom; Precip: Nil Wind: Light, NE | Mod, NE at ridgetop.Thursday: Sky: Clear; Freezing Level: Valley Bottom; Precip: Nil Wind: Light, NE Friday: Sky: Clear; Freezing Level: Valley Bottom; Precip: Nil Wind: Light, NE

Avalanche Summary

Explosive control work on a steep north facing slope in the alpine produced an anomalous size 2.5 avalanche in the central portion of the region Saturday. On Sunday/Monday activity was limited to skier provoked sluffing.

Snowpack Summary

The January 29th system left 10 - 20 cm of snowfall in it's wake with the greatest accumulations in the southern portion of the region.  North winds redistributed the snow resulting in reverse loading of lee features in the alpine with reactive pockets of wind slab up to 40cm deep.The new snow and wind slabs rest on a significant weakness composed of of large surface hoar (widespread in most sheltered and shaded areas at all elevations), a sun crust on south facing slopes, faceted grains (in colder areas or areas with a thinner snowpack), or a combination of the above. This variable weak layer is expected to become a problem when/if it finally starts snowing again. The rest of the upper and mid-snowpack are generally well consolidated.In isolated areas where the snowpack is thinner or in steep rocky features a facet/crust weakness near the ground remains a concern. In most places the depth of this layer combined with the strength of the overlying slab makes triggering an avalanche unlikely. However, if you were unlucky enough to find a weak spot the consequences could be deadly serious.

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.