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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

Kootenay Boundary.

Confidence

Fair - Due to variable snowpack conditions

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 around lunch time.

Avalanche Summary

Several reports of both natural and human triggered loose snow avalanches from steep terrain to size 1.5. Isolated skier controlled wind slabs to size 1 at ridge top. 

Snowpack Summary

10 cm of light density snow fell Thursday adding to the 60 cm of settled storm snow that rests on the January 4th interface which consists of small facets, surface hoar (up to 12mm) in sheltered treeline and below treeline areas and sun crust on steep south and west facing slopes. The bonds at this interface are improving.  The layer is still alive and well in test pits but has not been reactive to human triggering in the last day or so.  Wind slabs created by the previously raucous SW winds have grown old & tired. The midpack is well bonded and strong. The November 28 surface hoar is still being found in isolated, sheltered below treeline locations buried 120cm. The deep crust/facet combo from early November still exists but seams to have gone dormant for the time being.

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.