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Avalanche Forecast

Archived

Mar 9th, 2016–Mar 10th, 2016

Alpine
Natural and human triggered avalanches likely.
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 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.

Regions

Little Yoho.

If the forecast storm reaches this far north we will likely see a small avalanche cycle. The snowpack should moderate fairly quickly.

Weather Forecast

A big system is forecast for Thursday. Models are showing 20 - 40 cms with moderate to strong SW winds and freezing levels rising to ~ 1900m. The danger ratings will rise rapidly if it materializes.

Snowpack Summary

15 to 30 cm of new snow sits on a well settled mid and lower pack. This new snow overlies a temperature crust below 1800m on polar aspects and a sun crust into the alpine on solar aspects. Isolated wind effect exists near ridge-tops. No significant shears found in the mid and lower pack, however thin snowpack areas are still suspect.

Avalanche Summary

We received a report on Monday of a skier triggered avalanche on the Wapta near Mt. Collie and the Richard and Louise Guy Hut. It was a size 2.5 on a SE aspect at 2600m. This failed on a facet layer near the base of the snowpack and took two skiiers for a ride, partially burying one with minor injuries.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

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.

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.