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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.
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

Kootenay Boundary.

Confidence

Good

Weather Forecast

Sunday: Inversion. Freezing level at surface. Above freezing layer from 1500m – 2200m. Ridgetop winds Strong NW. Treeline winds moderate NW. No precipMonday: Inversion. Freezing level at surface. Above freezing layer from 1500m – 2200m. Ridgetop winds Strong NW. Treeline winds light W. No precipTuesday: Inversion. Freezing level at surface. Above freezing layer from 1500m – 2200m. Ridgetop winds Strong NW, switching to strong W as ridge flattens in the afternoon. Treeline winds light W switching SW after lunch. No precip

Avalanche Summary

No new natural activity. On Friday a group of skiers triggered a small (size 1.5) hard slab avalanche the failed when the 3rd skier traversed across an east facing slope at 2000m.

Snowpack Summary

Savage winds out of the NW have wreaked havoc on the region.  N & W facing slopes are wind pressed or wind-stripped.  Slopes lee to these winds were left with wind slabs up to a meter in depth in open areas. Warm temperatures have created moist snow that can be found on almost all aspects up to 2300m.  Protected areas are growing surface hoar to 10mm, while many other slopes are sporting a zipper crust due to the warm temps.  Under the snow surface lies the January 4th interface, down around 75 cm & obviously much deeper in wind loaded areas.  This layer of small/facets/crusts and intermittent surface hoar is producing planar shears in some drainages and no failure at all in others.  At the moment it's tough to find soft snow to recreate in.  The midpack is well good, nicely bonded and strong.

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.