Avalanche Forecast

Issued: Dec 25th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada MBender, Avalanche Canada

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 Deeply buried weak layers continue to be a concern. If triggered, avalanches running on these weak layers will likely be large and destructive. Choose conservative terrain. 

Summary

Confidence

Low - Uncertainty is due to the limited number of field observations. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

FRIDAY NIGHT: Cloudy with isolated flurries, light south wind, alpine temperature near -10 C.

SATURDAY: Scattered flurries, accumulation 5-10 cm, light to moderate southwest wind, alpine temperature near -8 C.

SUNDAY: Mainly cloudy with sunny breaks, light to moderate west wind, alpine temperature near -8 C.

MONDAY: Mix of sun and cloud, light west wind, alpine temperature near -10 C.

Avalanche Summary

Thursday's reporting showed a naturally triggered size 3.5 persistent slab avalanche running in the alpine on a southeast aspect. There was also a report of size 2.5 naturally triggered windslab in the alpine on a south aspect. 

On Wednesday there was a report of several size 3 to 4 explosives controlled persistent slab avalanches in the south of the region along the Highway 1 corridor. These ranged from south and east aspects to northeast running from the alpine to the valley floor. 

Snowpack Summary

Snow falling last week has been redistributed by winds blowing from a veriety of directions at upper elevations. Underneath this storm snow there is a sandwich of weak layers which are widespread throughout the region.

About one meter below the surface is the mid December surface hoar. This layer has recently been sensitive to human triggering.

Below that lies the early December persistent weak layer, it's about 80 to 140 cm below the surface. This weak layer is a mixed bag that often presents as surface hoar and facets sitting on top of a supportive crust. This is a nasty weak layer, when avalanches fail on it, they have been large and destructive. Smaller avalanches in motion can step down to this one too. 

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs

Wind switching directions has created wind slabs on a variety of aspects.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

A slab rests on a persistent weak layer which has the capacity to propagate avalanches across terrain features. Although the likelihood of triggering a persistent slab avalanche is reducing, the potential for triggering a high consequence avalanche should still be top of mind in your decision making process.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Dec 26th, 2020 4:00PM