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Avalanche Forecast

Archived

Nov 26th, 2020–Nov 27th, 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 possible, human triggered probable.
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

North Columbia.

Strong winds and new snow will form fresh slabs that will likely become more reactive throughout the day. Avoid overhead hazard in times of high winds. Higher snowfall amounts in the north may mean that riding areas near Valemount are more in line with the Cariboos forecast.

Confidence

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

Weather Forecast

THURSDAY NIGHT - Flurries, 5-15 cm / southwest wind, 40-60 km/h / alpine low temperature near -7 / freezing level 900 m

FRIDAY - Flurries, 5-15 cm / southwest wind, 40-60 km/h, gusting to 80 km / alpine high temperature near -6 / freezing level 1100 m

SATURDAY - A mix of sun and cloud with isolated flurries / west wind, 20-40 km/h, easing in the afternoon / alpine high temperature near -7 / freezing level 900 m

SUNDAY - A mix of sun and cloud / south wind, 20-30 km/h / alpine high temperature near -5   

Avalanche Summary

Storm slabs are expected to become increasingly reactive throughout the day with the arrival of new snow and strong winds.

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 North 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

5-15 cm of new snow on Thursday night with another 5-15 cm expected on Friday will arrive with strong southwest winds. The biggest snowfall amounts are expected to be in the northern half of the region. Storm slabs will likely be widespread in the region. A crust from early November exists down approximately 90-130 cm. This crust has been observed to have weak, sugary facets above and below it. Recent tests on this layer indicate that it may be bonding poorly, and has the potential to be triggered by humans. 

Terrain and Travel

  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.