Avalanche Forecast
Issued: Dec 22nd, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
swerner,
Avalanche Canada
This forecast is based on 15-25 cm of new snow accumulating throughout the day on Wednesday. If you see higher amounts, especially earlier in the day consider bumping the hazard up to HIGH. Fresh storm slabs will likely increase in reactivity in the afternoon.
Summary
Confidence
Weather Forecast
Heavy snow and strong wind will arrive with the strong Pacific frontal system.
Wednesday: Snow heavy at times 15-25 cm accumulating through the day. Alpine temperatures near -3 and freezing levels 600 m. Ridgetop wind strong from the South.
Thursday: Heavy snow with 20-30 cm accumulating. Alpine temperatures -3 and freezing levels 600 m. Ridgetop wind switching to the East.
Friday: Cloudy with isolated flurries. Alpine temperatures near -1 and freezing levels 1000 m.
Avalanche Summary
On Tuesday at the time of publishing only a few size 1 avalanches were reported from steep West aspects.
On Monday a few natural avalanches up to size 2.5 were reported near Terrace. Also, explosives control work triggered a few size 2 avalanches. I suspect natural avalanche activity will taper off tomorrow but human triggered avalanches remain likely.
Please consider sharing your observations with the Mountain Information Network; even just a photo of your day helps. Thank you to those that have already submitted this winter!
Snowpack Summary
The incoming storm will likely build new and reactive storm slabs, especially where the snow has been stiffened by the wind and/ or sit above a recent surface hoar layer buried 40 cm down. I'm uncertain with widespread this buried interface is throughout the region besides the Nass Valley. Check out this awesome Facebook Post showing its sensitivity to human triggers.
A crust that was buried in early December is now down 80-120 cm in the alpine but is closer to the surface at and below treeline elevations. Around this crust are facets and potentially surface hoar in sheltered areas. Storm slabs may step down to this layer.
The early-November crust is buried around 100-200 cm at treeline. This crust may have weak and sugary facets above it in parts of the region. Uncertainty remains about where this layer remains a problem in the region, but it may be localized to the northern half of the region.
Terrain and Travel
- Watch for changing conditions today, storm slabs may become increasingly reactive.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Be especially cautious as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Storm Slabs
Fresh storm slabs building Wednesday and Thursday will likely be reactive, especially to human triggers. Due to the timing of the storm, the avalanche hazard could increase throughout the day.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A crust that was buried in early December is now down 80-120 cm in the alpine but is closer to the surface at and below treeline elevations. Around this crust are facets and potentially surface hoar in sheltered areas. Human triggered avalanches and storm slabs may step down to this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 23rd, 2020 4:00PM
