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Avalanche Forecast

Archived

Jan 12th, 2013–Jan 13th, 2013

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

Regions

South Columbia.

Confidence

Fair - Freezing levels are uncertain for the entire period

Weather Forecast

Sunday: Light N wind. Alpine temperature near -12. No snow.Monday: Moderate NW wind. Alpine temperature near -5. Light snow.Tuesday: Moderate NW wind. Alpine temperature near -3. No snow.

Avalanche Summary

A natural and human-triggered cycle of size 1-3 storm slabs occurred last week. Many were failing on buried surface hoar or facets. Natural activity has decreased, but human-triggering remains a concern.

Snowpack Summary

50-90 cm of recent snow is settling over old snow surfaces including surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of buried surface hoar is patchy, but where it exists, it may still be touchy. Many operators are cautiously optimistic that it is showing an improved bond. Recent winds have left wind slabs in the lee of terrain breaks such as ridges and ribs at alpine and treeline elevations. In areas sheltered from the wind, fast-moving sluff could throw you off your feet or carry you into a terrain trap. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

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.

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.