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Avalanche Forecast

Archived

Nov 25th, 2020–Nov 26th, 2020

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 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.

Welcome to the winter 2020/2021 forecast season! Watch for reactive storm 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- Mainly cloudy with scattered flurries / southwest wind, 30-40 km/h / alpine low temperature near -9

THURSDAY- Increasing cloud, snow beginning in the afternoon / southwest wind, 20-40 km/h / alpine high temperature near -7 / Freezing level 1000 m 

FRIDAY- Snow, 10-15 cm / southwest wind, 30-50 km/h / alpine high temperature near -5 / Freezing level 1000 m

SATURDAY- A mix of sun and cloud / west wind, 15-20 km/h / alpine high temperature near -8 / Freezing level 900 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 2-3 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

Up to 25 cm of recent fresh snow brings recent storm snow totals to anywhere between 20-50 cm. A crust from early November exists down approximately 80-100 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

  • Avoid freshly wind loaded terrain features.
  • In times of uncertainty conservative terrain choices are our best defense.
  • If it's deep enough to ride, it's deep enough to slide (avalanche).

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.