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Avalanche Forecast

Archived

Nov 27th, 2020–Nov 28th, 2020

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

Regions

Kananaskis.

Its been ridiculously windy the past 24 hours. Our snowpack has dramatically changed and will require us to start from scratch and re-learn its character. Don't casually approach terrain as if it was still last week's snowpack. 

Confidence

High -

Weather Forecast

The upper alpine winds will fade overnight tonight and settle to a relative calm of 50km/hr out of the west. At treeline they should be around 10-20 km/hr and also westerly. A flurry or two will give a centimeter or two of snow. And temperatures will steadily fall to -7 by mid afternoon. 

Avalanche Summary

Several wind induced loose dry avalanches from alpine gullies. We also witnessed a healthy sz2 near Mt Storelk. It likely started with a cornice fall and triggered slope as it travelled. 

Snowpack Summary

The last 24 hours have been extremely windy, even for us. Highwood pass had a few small patches of preserved snow, but for the most part, our snow has blown to Saskatchewan. Widespread wind affect is an understatement. That means our two weak layers will be at different depths than what we've known so far. Take some time to dig and re-familiarize yourself with the layers and their reactivity. The crust may be much deeper than we expect and surface windslabs will be widespread and stiffer than usual. Expect them to become more "triggerable".

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Avoid steep convex slopes.
  • Pay attention to isolated alpine features as well as cross-loaded features at treeline.

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.