Avalanche Forecast

Issued: Nov 27th, 2012 9:07AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

ccampbell, Avalanche Canada

Sea To Sky.

Avalanche danger is set to rise with stormy weather.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Wednesday: Snow with 15-20cm of accumulation, freezing levels around 1500m, and moderate to strong southerly winds. Thursday: Snow with 20-40cm of accumulation concentrated in immediate coastal areas, freezing levels around 1400m, and strong southerly winds. Friday: Continued snowfall with another 20-30cm again concentrated to immediate coastal areas, freezing levels remaining at 1400m, and strong southerly winds.

Avalanche Summary

Reports from the Whistler area yesterday include a Size 2.5 deep slab avalanche running on the early November facet/crust combo triggered with small explosives low on the slope. Check out Wayne Flann's Avalanche Blog for more information, including photos. Also of note, there was a report of a size 2.5 skier triggered avalanche on Saturday. This avalanche occurred on a northeast aspect in the alpine. It was triggered from the bottom of the slope, and likely released on the early November layer. Fresh wind slabs have been touchy and wet loose natural point-release sluffs have been observed on sun-exposed slopes.

Snowpack Summary

The snow surface consists of large surface hoar, a thin sun crust, surface facets, moist snow, or preserved storm snow depending on elevation, sun and wind exposure, slope angle, time of day, and aspect; all of which could become weak layers once buried by a sufficiently cohesive slab. A storm snow instability has been noted down 30 cm, giving consistent moderate "pops" results in snowpack tests. Snowpack tests continue to show sudden collapse (or "drops") results on the early November facet/crust deep persistent weakness, but because this weakness is so close to the ground in most areas, associated avalanche activity will likely be limited to slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, glaciers, etc.). For more information check out the telemarktips.com forum , the Mountain Conditions Report, and Wayne Flann's Avalanche Blog.

Problems

Wind Slabs

Expect to find weak wind slabs below ridgecrests, behind terrain features, and in cross-loaded gullies. Natural avalanche activity is possible with heavy loading from snow and wind, and human triggering is likely, especially on steep convex slopes.

Assess start zones carefully and use safe travel techniques.>Avoid freshly wind loaded features.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

Slopes with smooth ground cover and reloaded bed surfaces. Prone to remote triggering and step down avalanches. Typical trigger points include thin rocky areas. May be difficult to trigger, but often very large with serious consequences.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propagate to deeper instabilites.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Nov 28th, 2012 2:00PM