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Avalanche Forecast

Archived

Nov 25th, 2020–Nov 26th, 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

Purcells.

Welcome to the winter 2020/2021 forecast season! Watch for reactive wind slabs at upper elevations, and be aware of the potential for larger avalanches due to a crust that was buried in early November 

Confidence

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

Weather Forecast

WEDNESDAY NIGHT- Cloudy with clear periods and isolated flurries / west wind, 20-40 km/h / alpine low temperature near -9

THURSDAY- Cloudy with sunny periods and isolated flurries / west wind, 20-40 km/h / alpine high temperature near -7 / Freezing level 1000 m

FRIDAY- Cloudy with sunny periods and isolated flurries / southwest wind, 30-50 km/h / alpine high temperature near -5 / Freezing level 1000 m

SATURDAY- Mainly cloudy with scattered flurries / southwest wind, 15-20 km/h / alpine high temperature near -5 / Freezing level 1000 m 

Avalanche Summary

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 avalanches reported on the early November crust. These have been triggered by both humans and explosives.

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

Snowpack Summary

The Purcells have seen up to 30 cm of fresh snow this week. There is a crust from early November that is down approximately 50-75 cm. This layer has been observed to have weak, sugary facets above and below it. Recent observations of this layer indicate that it has the potential to be triggered by humans.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • In times of uncertainty conservative terrain choices are our best defense.

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.