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Avalanche Forecast

Archived

Dec 17th, 2021–Dec 18th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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 unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Avoid "thick to thin" areas and steep roll overs, especially in wind effected terrain. Persistent slabs are challenging to manage. When in doubt choose more conservative terrain.

Confidence

Moderate -

Weather Forecast

Friday night: Low of -14 at 1700m. No new snow expected. Winds will be moderate from the Southwest.

Saturday: A storm arrives bringing 20 to 40cm of new snow with the greatest snowfall at Kootenay Pass. Strong Southwest winds. High of -8 at 1700m.

Sunday: light winds and no new snow expected. High of -6 at 1700m.

Monday: Some flurries in the afternoon with moderate Southwest winds. High of -7 at 1700m.

Avalanche Summary

A size 1.5 skier accidental was observed in a part of the South Columbia region that has similar snowpack conditions to the Kootenay boundary. This avalanche failed on the facets above the early December crust which was down 35cm on a North aspect at 2200m.

Snowpack Summary

The incoming weather will form new wind slab in exposed terrain.

The defining feature of the snowpack is a widespread crust that now sits 30-80cm below the surface. In some places overlying snow is well-bonded to the crust but in others, including Kootenay Pass, weak faceted grains have been observed above it around treeline.  

Snow depths are roughly 140-180 cm at treeline throughout the region.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.