Avalanche Forecast
Issued: Dec 19th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs.
ghelgeson,
Avalanche Canada
Small wind slabs likely exist in extreme terrain near ridge crest. Avoid areas where the snowpack goes from thick to thin as we have a lingering deep persistent slab avalanche problem that can't be totally ruled out.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT: Overnight low temperature around -22, light north/northwest wind, no snow expected.
MONDAY: A few clouds, daytime high temperature around -15, moderate to strong west/northwest wind, no snow expected during the day, 3 to 6 cm possible Monday night.
TUESDAY: Overcast, daytime high temperature around -10, strong north/northeast wind, 2 to 6 cm of snow possible.
WEDNESDAY: Broken cloud cover, daytime high temperature around -15, strong north wind, no snow expected.
Avalanche Summary
This MIN from Saturday shows a small wind slab in a terrain feature known for producing these kinds of avalanches. Other than that, we haven't had any recent avalanche observations, it was pretty quiet and beautiful in the White Pass this weekend.
On December 1, a size 2.5 avalanche was remotely triggered by a recreational group on Log Cabin. This avalanche likely failed on the weak, sugary snow at the bottom of the snowpack.
Snowpack Summary
There's been a glorious inversion in place, and small surface hoar is forming in the valley fog.
The White Pass is looking heavily wind effected, as evidenced in this MIN. Recently winds have been out of the southwest and northwest. Wind slabs are almost always present in the mountains, watch for small wind slabs immediately lee of ridge crest.
The middle snowpack is supportive to travel but snow depth still varies greatly with aspect and elevation.
A layer of weak, sugary snow at the base of the snowpack has been observed in most areas. This layer has been inactive since early December, but it might still be possible to trigger this deeply buried layer in shallow snowpack areas. A cornice fall or surface avalanche impacting a slope may also have the potential to trigger it.
Terrain and Travel
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Deep Persistent Slabs
This layer is deeply buried and there has been very little activity on it since December 1st.
Most likely trigger points are areas where the snowpack goes from thin to thick, such as rock outcroppings. A large trigger like a cornice fall or avalanche in motion could potentially activate this deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 20th, 2021 4:00PM
