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Avalanche Forecast

Archived

Dec 18th, 2013–Dec 19th, 2013

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

Regions

Little Yoho.

Basal weaknesses are waking up with the added snow load. Avalanche control today produced large, destructive avalanches.  Use caution in avalanche terrain!

Weather Forecast

Cooling temps (-15 to -25) and clearing skies for Thursday.  Possibly some light precipitation on Friday/ Saturday.  Light SW/W winds throughout the period

Snowpack Summary

Another 10-20 cm of new snow today brings the storm snow total to 40-60 cm. Moderate to strong winds have created touchy windslabs in the alpine and at treeline.  Basal facets, depth hoar and the october rain crust are prominent at the base of the snowpack.

Avalanche Summary

Avalanche control work today on the Sunshine road produced large avalanches (size 2.5-3) on 6 of 9 shots. These avalanches appeared to initiate in the storm snow and step down to the October crust.  Similar reports from the Sunshine avalanche control team and a report of a size 2.5 natural near Bow Summit indicate widespread instability.

Confidence

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.