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Avalanche Forecast

Archived

Jan 19th, 2013–Jan 20th, 2013

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

South Rockies.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Sunday: Inversion. Freezing level at valley bottom. Potential for another above freezing layer to develop in the afternoon from 1500m – 2200m. Ridgetop winds Strong NW. Treeline winds moderate NW. Isolated flurries, no significant accumulations.Monday:  Inversion. Freezing level at valley bottom. Above freezing layer from 1500m – 2200m. Ridgetop winds Strong NW. Treeline winds light W. No precipTuesday: Freezing level should stick around valley bottom all day. Ridgetop winds Strong W, switching to extreme SW as ridge flattens in the afternoon. Treeline winds Mod to strong SW. No precip

Avalanche Summary

Loose snow avalanches continued Friday driven by strong SW winds. Activity was greatest on steep solar aspects which produced loose snow avalanches to size 1.5.  We received a couple of different reports of skiers intentionally triggering size 1 avalanches in cross loaded gulley features.

Snowpack Summary

Intense recent winds have redistributed snow and created large cornices. The snow surface is now a mix of sastrugi, hard slab and soft slab in open areas.  With the warm temps, slopes receiving direct sun are moistening in the afternoon.  Surface hoar is continuing to form in protected areas too. Below this around 60cm of settled 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. Reports indicate that this bond has strengthened over time and is now fairly tight. The overlying slab has also settled significantly. The bond at this interface seems to have strengthened somewhat with time. The overlying slab has also settled significantly.  There are some reports of glide cracks on Mt Fernie, these mysterious phenomena should be given a wide berth.

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.