Avalanche Forecast

Issued: Dec 16th, 2020 4:00PM

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

Avalanche Canada swerner, Avalanche Canada

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Up to 15 cm of new storm snow and strong southwest wind has likely formed fresh new wind slabs on northeast though southeast slopes and behind terrain features. Stiff snow and cracking are indicators of a potential wind slab avalanche problem.

Summary

Confidence

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

Weather Forecast

A brief period of high pressure will bring a mix of sun and cloud to the region on Thursday and Friday. Ridgetop wind will be strong from the southwest with freezing levels as high as 1100 m. The next frontal system is expected this weekend bringing new snow, strong to extreme winds and rising freezing levels near 1500 m.

Avalanche Summary

No new avalanches reported on Wednesday.

A wind slab avalanche likely stepped down to the weak faceted grains described in the snowpack summary, forming a large avalanche near Smithers within the past few days.

Data in this region is very sparse. Please consider sharing your observations to the Mountain Information Network; even just a photo of your day helps. Thank you to those that have already submitted this winter.

Snowpack Summary

Up to 15 cm of new snow and strong wind from the southwest have built the freshest wind slabs on the northeast facing slopes at treeline and in the alpine. Older wind slabs may still be found on other slopes from the East winds early this week. These slabs may overly a melt-freeze crust from early December, which may have weak and sugary faceted grains growing around it.

At the base of the snowpack sits the early-November crust with weak faceted grains below. These faceted grains have formed large avalanches in both the south and north of the region within the past week.

Snowpack depths vary substantially with aspect, elevation, and wind exposure. Below treeline the terrain may still be below the threshold for avalanches

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

Wind Slabs

An icon showing Wind Slabs

10-20 cm of new snow and strong wind from the southwest will build the freshest slabs on northwest to northeast to southeast aspects. Older wind slabs may still linger on southwest slopes due to strong easterly winds earlier this week. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Weak faceted grains near the base of the snowpack have the potential of forming large and destructive avalanches. The most likely place to trigger this layer would be on shallow and rocky slopes. Smaller wind slab avalanches would also have the potential of stepping down to this layer.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 17th, 2020 4:00PM