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Avalanche Forecast

Archived

Dec 10th, 2011–Dec 11th, 2011

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

Regions

Purcells.

Confidence

Fair - Due to limited field observations

Weather Forecast

Sunday: Expect clearing skies, with light winds and temperatures reaching -10. Monday: Mostly clear, with winds turning westerly but remaining light. Freezing levels could reach 1200m. Tuesday: Expect clouds to build and light flurries to begin late in the day under southwesterly winds.

Avalanche Summary

No new avalanches.

Snowpack Summary

Surface hoar continues to grow and the cold weather is penetrating into the upper snowpack giving near surface facetting. Steep south facing slopes may have developed a thin sun-crust. Windslabs continue to lurk in lee areas in the alpine and open treeline. Snow depths are quite variable through the region with 130-150cm in the alpine. There is still concern for triggering the weak basal facets/depth hoar, as these layers have shown sudden collapse results in stability test in shallow areas.

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.