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Avalanche Forecast

Archived

Nov 27th, 2012–Nov 28th, 2012

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

Avalanche danger is set to rise with stormy weather.

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Wednesday: Snow with 5-15cm of accumulation, freezing levels around 1700m, and moderate to strong southerly winds. Thursday: Snow with 20-30cm of accumulation, freezing levels around 1500m, and strong southerly winds. Friday: Continued snowfall with another 15-20cm, freezing levels remaining at 1500m, and extreme southerly winds.

Avalanche Summary

Check out Wayne Flann's Avalanche Blog for a photo of a recent large avalanche off the north face of Mt. Currie. After a brief lull, avalanche activity will likely pick up again with forecast wind and snow.

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. The main snowpack feature is a rain crust buried early November and now down around 60-80cm at treeline. A weak layer of facets sitting on top of this crust shows "sudden" fracture character and the ability to propagate into large avalanches if triggered, 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

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.