Avalanche Forecast

Archived

Dec 27th, 2012–Dec 28th, 2012

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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells.

Confidence

Fair - Wind speed or direction are uncertain on Saturday

Weather Forecast

Friday: Isolated flurries with overcast skies, winds light from the west. Alpine temperatures near -10.Saturday: Light precipitation, winds will be light west and northwest. Alpine temperatures will be near -10.Sunday: A weak ridge of high pressure should bring drier conditions with upper level temperatures remaining cool.

Avalanche Summary

There was recent (Dec 26) report of a size 3 skier triggered avalanche in the Dogtooth range. Triggered from a thin area on a cross-loaded west facing feature at the upper end of the tree-line elevation, it then stepped down to the early November crust. There are no other observations to report at this time.

Snowpack Summary

A wind event from last week formed relatively deep wind slabs in the alpine. New snow combined with wind has formed fresh wind slabs on the surface and/or buried newly formed surface hoar in sheltered, open areas at and below tree line. The mid-pack is reported to be settling well. Recent reports indicate the late November surface hoar (near the middle of the snowpack) and early November crust (near the base of the snowpack) have been mostly inactive as of late. It's important to note that professionals are still cautious about these lingering persistent slab problems, but the likelihood of triggering is low. Be wary of steep complex terrain with a shallow snowpack, where triggering a persistent weakness is more likely.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.