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Avalanche Forecast

Archived

Feb 21st, 2021–Feb 22nd, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
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.

Regions

Kananaskis.

20cm of new snow coupled with extreme SW winds on Sunday night and Monday morning will push the hazard levels to HIGH. Avoid avalanche terrain.

Confidence

Moderate -

Weather Forecast

It's windy! Sunday evening will see wind speeds reaching 150km/h at ridgetop out of the SW and there is a wind warning in effect. By Monday morning the winds will slow down to 100km/h, and further decrease to 50km/h by the afternoon. Even for K-country this is extreme winds. Temperatures on Monday should climb to -5 by midday, and as much as 20cm of new snow is expected at Treeline elevations, with possibly rain in the Bow Valley.

Avalanche Summary

No new avalanche activity was observed Sunday, but visibility was limited.

Snowpack Summary

Extreme winds on Sunday are stripping all the remaining snow from windward aspects and depositing that snow into lee and cross-loaded features. Wind slabs are widespread at Treeline and above, and can even be found in open areas at lower elevations. The depths of the wind slabs are highly variable (5 to 80cm), as is the sensitivity to triggering. In exposed Alpine areas expect hard, dense wind slab conditions, but as you loose elevation these slabs are softer and potentially more triggerable. Be mindful of rapidly changing conditions as you travel through the terrain.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Watch for areas of hard wind slab on alpine features.
  • Avoid lee and cross-loaded 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.