Avalanche Forecast
Issued: Dec 20th, 2021 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.
ghelgeson,
Avalanche Canada
New snow and extreme wind are expected to induce a natural avalanche cycle and make mountain travel downright inhospitable. Avoid all avalanche terrain Tuesday.
Summary
Confidence
Weather Forecast
Prepare for wind my friends.
MONDAY NIGHT: Overnight low temperature around -15, moderate to strong west/southwest wind, 5 to 10 cm of snow.
TUESDAY: Overcast, daytime high temperature around -12, strong to extreme north/northeast wind, 2 to 6 cm of snow possible.
WEDNESDAY: Broken cloud cover, daytime high temperature around -15, strong to extreme north/northwest wind, no snow expected.
THURSDAY: Broken cloud cover, daytime high temperature around -18, 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 last 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 was a glorious inversion in place, and small surface hoar has formed where there was valley fog, like a ring around a bathtub. It all changes Monday night as wind picks back up, and it begins to snow once again. Widespread fresh storm slabs are expected to be forming Tuesday.
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
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
10 to potentially 20 cm of storm snow and extreme wind are expected to form fresh storm slabs Monday night into Tuesday and there is potential for a natural avalanche cycle.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
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 21st, 2021 4:00PM
