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Avalanche Forecast

Archived

Nov 27th, 2020–Nov 28th, 2020

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

Regions

South Columbia.

  

Recent strong southwest winds have created fresh wind slabs on lee features at treeline and above. Use caution when transitioning into wind affected terrain.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

FRIDAY NIGHT: Cloudy w/ flurries; 3-5 cm. / Moderate to strong, southwest wind / alpine low temperature -7 / Freezing level 800 m.

 SATURDAY: Mix of sun and cloud / Light, south wind / alpine high temperature -6 / Freezing level 1000 m.

 SUNDAY: Mix of sun and cloud / Light, south wind / alpine high temperature -6 / Freezing level 800 m.

 MONDAY: Snow, 5-10 cm / Moderate, south wind / alpine high temperature -3 / Freezing level 1200 m.

Avalanche Summary

  

Recent strong southwest winds have created fresh wind slabs on lee features at treeline and above.  

There have been very few reports of avalanches in the region, however observations are limited at this time. 

In the past week there have been a few size 2-3 avalanches reported on the early November crust in both the South Columbia and neighbouring Glacier National Park region.  

If you get out into the mountains, please consider sharing your observations on the Mountain Information Network!

Snowpack Summary

  

Recent strong southwest winds have created fresh wind slabs on lee features at treeline and above. There are a couple of crusts in the mid snowpack, from mid and early November. The most prominent of these is from early November, and it has been reported that there are weak, sugary facets above and below this crust. It is down approximately 70-100 cm, and recent observations indicate that this layer has the potential to be triggered by humans. Several reports indicate that it is likely the most reactive on south facing slopes.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.