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Avalanche Forecast

Archived

Nov 20th, 2020–Nov 21st, 2020

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

Regions

Kananaskis.

Light snow and strong north winds have created pockets of reverse loaded windslabs. Recognizing the variable depth snowpack is critical right now. Both of our avalanche problems will be worse in thin areas. 

Confidence

Moderate -

Weather Forecast

A few scattered flurries tonight won't offer much for new snow. A bit of morning cloud will break up by 11am and hopefully offer some blue skies. Temperatures will be consistent at about -7. Alpine winds will be around 40-50km/hr from the west.

Avalanche Summary

One size 2 on an east facing, high alpine slope near Mt Lawson. It was about a meter deep and ran a couple hundred meters. 

Snowpack Summary

We continue to get small, but continuous new snow fall. At the moment there is about 10cm of new snow from the last few days. The north winds today have redistributed it into a more variable pattern. We are seeing anywhere from 20-50cm on top of the crust. With that, snow depth also varies dramatically. Rolls in the terrain are very thin, while concave areas are 90cm deep. The crust is very apparent, down 50 in today's profile. In some areas there is a slippery facet layer above it and in others it is well bonded with surface layers. Ground cover seems to be the link here. Rocky/gravel areas have a more pronounced facet layer. And it wouldn't be a snow pack structure summary without the mention of our ever-present wind slabs. These are concerning near ridges and immediate lee areas.

Terrain and Travel

  • Avoid areas with a thin or variable snowpack.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.