Avalanche Forecast

Archived

Dec 12th, 2013–Dec 13th, 2013

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

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

South Coast.

Confidence

Fair - Due to the number of field observations

Weather Forecast

The latest weather models are predicting less precipitation for the region than previously forecast.Friday: Light precipitation will taper off early in the day. Ridge top winds will be light to moderate from the west. Freezing levels will hover between 1300 1500m.Saturday: The arrival of a weak warm front will bring between 5 and 15cm of snow to the alpine with moderate southwesterly winds. Freezing levels will rise through the day up to 1800m.Sunday: Expect partly cloudy skies and a cooling trend in the wake of the frontal system.

Avalanche Summary

No recent avalanche have been reported

Snowpack Summary

Snowpack depths vary greatly across the region with 160cm at treeline in the Cascades but only 50cm along the Duffy. Terrain below treeline is still mostly below threshold for avalanche activity.The snow forecast for Thursday failed to materialize with only light accumulations across the region barely covering a variety of old surfaces. Closer to the coast where the recent arctic outflow winds were stronger a thin layer of facets covers a crust on wind scoured north and northeast slopes. In sheltered locations, surface hoar could be found both at treeline in the alpine.A few crusts can be found near the ground, especially at higher elevations. The cold temperatures may have weakened the snow around these crusts - especially in alpine areas with a thinner snowpack such as moraine features.

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.