Avalanche Forecast
Issued: Dec 15th, 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
Triggering the Dec 1st surface hoar is still possible in areas that have not avalanched and the safest way to manage this problem, is through conservative terrain choices.
Summary
Confidence
Avalanche Summary
Thurs overnight the wind triggered two sz 2.5 natural avalanches off the north face of Mt. Macdonald.
On Thurs near the park boundary, an experienced group triggered a size 2 avalanche on the Dec 1 surface hoar and 1 skier was partially buried.
On Tuesday, a group triggered a size 2.5 on Ursus Minor. This avalanche was triggered in a wind loaded pocket near ridge top, in a shallow & faceted snowpack. Wide, impressive propagation occurred on the Dec 1 surface hoar, facet layer.
Snowpack Summary
16cm of storm snow buries a new surface hoar layer, which sits on top a thin sun crust in steep terrain.
A rain crust down 40cm is present up to 2100m.
A weak layer (Dec 1 surface hoar) buried 80-110cm deep continues to produce 'sudden' results in snowpack tests and human triggered avalanches. The surface hoar sits on a sun crust on solar aspects at upper elevations.
The base of the snowpack is facetted at upper elevations.
Weather Summary
A weak system brings light precipitation while over the next few days a ridge of high pressure moves into the interior.
Tonight: trace precip, -6°, Strong SW winds
SAT: 5cm, -5°, Moderate SW Winds, Fz lvl 1300m
SUN: trace precip, -5°, Light SW Wind, Fz lvl 1300m
MON: Mostly cloudy, trace precip, High -1°, Fz lvl 1800m
Terrain and Travel Advice
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Problems
Storm Slabs
Watch for reactive slabs on lee features in the alpine and at treeline. This problem may be more likely to trigger in sheltered areas where surface hoar is present beneath the slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar is down 80-110 cm. This is a prime depth for rider triggering. To manage this problem, stick to conservative terrain. Below 2100m this layer may be bridged by a supportive rain crust.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 16th, 2023 4:00PM
