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Avalanche Forecast

Archived

Dec 10th, 2011–Dec 11th, 2011

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

Regions

South Columbia.

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

Isolated reports of small solar triggered sluffs on south facing slopes at treeline and in the alpine.

Snowpack Summary

The Surface Hoar continues to grow due to the clear and cold nights and the cold temperatures are also promoting near surface facetting. Expect to find a sun-crust that has formed in the alpine on south through west aspects. Wind slabs persist in the alpine and in large openings at treeline. Some areas have a rain-crust below treeline from the 28th of November that has been buried by about 20 cms of snow. This rain-crust may be developing facets, and could become a layer of interest after it is buried by more of a load. There is still some concern associated with the November 7 surface hoar layer. This layer is buried 100-150 cms. Tests are showing that this layer is getting harder to trigger, but if an avalanche does release on this layer, it is likely to be large and destructive.

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.