Avalanche Forecast
Issued: Dec 21st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
MM,
Avalanche Canada
A persistent weak layer of surface hoar mid-snowpack, is primed for human triggering. The safest way to manage this problem is through conservative terrain use.
Pushing into bold terrain in search of untracked lines, has resulted in several near-misses recently.
Summary
Confidence
Moderate
Avalanche Summary
On Wed/Thurs, several natural avalanches up to size 2.5 were observed running from the steep terrain of Mt. Macdonald.
Five significant human-triggered avalanches have occurred in the past week, all failing on the Dec 1st surface hoar layer. In the Connaught drainage a size 2.5 was triggered on Balu Peak, on Ursus Minor a skier narrowly avoided being carried over some cliffs, and in the Asulkan valley another avalanche was triggered near the 7 steps.
Snowpack Summary
Thurs's warm temps made for moist snow up to 2000m and up to 25cm overlies variable old surfaces: wind affect; a crust on steep, solar slopes; or surface hoar in sheltered areas.
The Dec 1 surface hoar, down 50-100cm, continues to produce 'sudden' results in tests and has been the culprit in several recent close calls from skier-triggered avalanches. Below 2100m, a rain crust is buried 40-50cm deep.
In shallow areas the base of the snowpack is faceted and unsupportive.
Weather Summary
A decent storm will bring new snow, high winds and as it leaves, cold temps.
Tonight: Trace precip, Light SW wind, Freezing level (Fzl) 1500m
Friday: 17cm, High -3°C, Mod-Strong SW wind, Fz lvl 1700m,
Saturday: Mix of sun/cloud. Low -14°C, High -11°C Mod SW Winds. Fz lvl valley bottom
Sunday: Mixed sun/cloud, Low -13°C, High -7°C, Light W wind. Fz lvl 900m
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Problems
Storm Slabs
Deeper wind-loaded features in the alpine and at treeline may still hold reactive slabs from the recent snow and warm temps. Allow time for this snow to settle and bond before stepping out into overly committing terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar down 50-100 cm in the snowpack is at the ideal depth for human triggering and remains reactive. To manage this problem, stick to conservative terrain. Below 2100m this layer may be bridged by a buried rain crust.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 22nd, 2023 4:00PM
