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Avalanche Forecast

Archived

Dec 15th, 2021–Dec 16th, 2021

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

Regions

Kootenay Boundary.

Avoid "thick to thin" areas near ridge tops where triggering avalanches will be more likely.

Confidence

Moderate -

Weather Forecast

Wednesday night: light flurries with light south wind. low of -9 at 1700m.

Thursday: some light flurries with a high of -8 at 1700m. Winds becoming light to moderate from the Northwest in the afternoon. 

Friday: no new snow with moderate Northwest winds and a high of -13 at 1700m.

Saturday: A storm arrives bringing up to 15cm of new snow and strong Southwest winds. High of -6 at 1700m.

Avalanche Summary

No new avalanches were observed in the region but 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

10cm of low density snow overlies old variably wind effected surfaces.

The defining feature of the snowpack is a widespread crust that now sits 30-70 cm below the surface. In many places overlying snow is well-bonded to the crust but in others, including Kootenay Pass, weak faceted grains have been observed growing above it around treeline.  

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

Terrain and Travel

  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Be careful as you transition into wind affected terrain.

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.