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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 Rockies.

Confidence

Fair

Weather Forecast

Sunday: Ridgetop winds light NW. Freezing level at valley bottom. No significant snowfall. 1500m temp: -10Monday:  Mod/Strong W/NW winds at ridgetop. Freezing level at valley bottom.  No significant snowfall.Tuesday: Freezing level rising to 2000m in the morning.

Avalanche Summary

Avalanche activity was limited to loose sluffs in steep terrain Friday.

Snowpack Summary

Around 50 cm of storm snow fell in favored locations earlier this week. This snow rests on a myriad of old surfaces (January 4th interface) that include sun crust on steep south and west facing terrain, surface hoar in sheltered locations at treeline and below and facets everywhere else. The bond at this interface is gaining strength. Our field team spent Friday in the Harvey Pass area hunting for this interface. They were unable to produce any failures on the interface in their test pits Wind slabs created during and just after last weeks storm have grown old and tired. The midpack is 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.

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.