Avalanche Forecast
Issued: Dec 17th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
swerner,
Avalanche Canada
If forecast snowfall amounts add up on Friday storm slabs may be reactive, especially on northeast to southeast slopes lee of the wind. Fresh avalanches, stiff snow, cracking and whumping are all indicators of a slab avalanche problem.
Summary
Confidence
Weather Forecast
Overnight Thursday: Snow 5-10 cm with strong West winds and freezing levels 500 m.
Friday: Snow 5-10 cm with strong southwest wind. Alpine temperatures near -2 and freezing levels 1100 m.
Saturday: Snow 10 cm. Strong southwest wind and freezing levels near 1000 m.
Sunday: Mix of sun and cloud, windy and freezing levels 900 m.
Avalanche Summary
No new avalanches reported on Thursday.
A wind slab avalanche likely stepped down to the weak faceted grains described in the snowpack summary, forming a large avalanche near Smithers earlier this week. With forecast new snow, strong winds, and rising freezing levels avalanche danger will likely be on the rise.
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. 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
- Watch for fresh storm slabs building throughout the day.
- 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
Storm Slabs
10-20 cm of new snow Thursday night and Friday accompanied by strong wind from the southwest will build fresh storm slabs. They may be more reactive on leeward slopes (NE-SE) where the wind has deposited deeper and stiffer slabs. Loose dry sluffing from steeper slopes and terrain features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
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
Expected Size
Valid until: Dec 18th, 2020 4:00PM
