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Avalanche Forecast

Archived

Jan 16th, 2013–Jan 17th, 2013

Alpine
Natural avalanches possible, human triggered probable.
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 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.

Regions

South Rockies.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

A mix of sun and cloud is expected for the forecast period. Extreme northwest winds are expected to ease to strong on Friday, and then become light on Saturday. The possibility of an inversion will exist throughout the period; however, alpine temperatures should stay below freezing.

Avalanche Summary

No new significant avalanche observations have been reported from the region.

Snowpack Summary

Light amounts of loose snow may overlie windslabs which exist in unusual locations due to strong northwesterly winds. Below this around 60cm of settled snow rests on a myriad of old surfaces that were buried on January 4th. These surfaces include a sun crust on steep solar aspects, surface hoar in sheltered locations at treeline and below, and facets everywhere else. The bond at this interface seems to have strengthened somewhat with time. The overlying slab has also settled significantly.The midpack is reportedly well settled and strong with one or two (location specific) crusts deep in the snowpack. These crust/facets combos are largely dormant, with the only concern being triggering from a shallow snowpack area or with a heavy trigger.Cornices in the region are reported to be large and potentially unstable.

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.