Avalanche Forecast

Archived

Dec 10th, 2013–Dec 11th, 2013

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 possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast.

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

The arctic air mass that has be sitting over much of BC for the last week is starting to retreat as a series of storm fronts drive warmer air into the province. Expect isolated flurries light winds from the southwest on Wednesday. The precipitation will intensify slightly on Thursday with southwest winds at ridgetop strengthening through the day. Friday will see a brief clearing with sunny periods and light winds.

Avalanche Summary

A large avalanche was recently reported as having failed on or close to the ground in the southern Cascades. This may be an isolated incident but could be indicative of a more widespread weakness at the base of the snowpack in the Alpine.

Snowpack Summary

Snowpack depths vary greatly across the region with 160cm at treeline in the Cascades but 50 cm along the Duffy. Terrain below treeline is still mostly below threshold for avalanche activity.Arctic outflow winds have redistributed the snows that fell last week forming wind slabs on S to SW slopes at treeline and in the alpine. Surface hoar has been growing over the last week in protected locations near tree line while the cold temperatures have driven faceting throughout the snowpack.A few crusts can be found near the ground, especially at higher higher elevations. Cold temperatures may have weakened the snow around these crusts - especially in alpine areas with a thinner snowpack.

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.