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Avalanche Forecast

Archived

Nov 29th, 2020–Nov 30th, 2020

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

Regions

Cariboos.

  

50-80 cm. of recent storm snow and moderate to strong southwest winds have formed widespread storm slabs ripe for human triggers. Additional snow and shifting northwest winds on Monday may form fresh wind slabs on lee features at treeline and above.

Confidence

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

Weather Forecast

SUNDAY NIGHT: Cloudy with flurries; 0-3 cm. / Moderate to strong, southwest wind / alpine low temperature -10 / Freezing level valley bottom.

 MONDAY: Snow, 5-15 cm / Moderate, northwest wind / alpine high temperature -6 / Freezing level 1000 m.

TUESDAY: Sunny / Light, northwest wind / alpine high temperature -8 / Freezing level valley bottom.

WEDNESDAY: Sunny / Light, south wind / alpine high temperature +2 / Strong inversion with an above freezing layer of air above 2000 m.

Avalanche Summary

A naturally triggered size 2.5 avalanche was reported on a southeast aspect in the alpine on Saturday.

Data is very sparse in this region. Please submit your observations to the Mountain Information Network.

Snowpack Summary

50-80 cm. of recent storm snow and moderate to strong southwest winds have formed widespread storm slabs ripe for human triggers. There is a crust from early November now down approximately 75-125 cm. This crust has been observed with sugary facets above and below it. There are limited observations on this layer, but some test results indicate that it has the potential to be reactive to human triggering. Total snowpack depths are an average of 100-200 cm at upper elevations, tapering quickly at lower elevations. 

Terrain and Travel

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid terrain traps where the consequence of any avalanche could be serious.
  • Avoid steep convex slopes.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.