Avalanche Forecast
Issued: Dec 5th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Fresh, reactive wind slabs are expected to form throughout the day. Watch for signs of instability such as whumpfing, cracking, and recent avalanches.
Concern remains for the persistent weak layers near the base of the snowpack. A conservative approach to terrain and is advised.
Summary
Confidence
Avalanche Summary
On Sunday, explosive control produced a large (size 2.5) wind slab avalanche on a southeast aspect in the alpine. This avalanche gouged down to the facetted lower snowpack in its track and as a result, entrained a large amount of mass.
On Saturday, a few, small (size 1) skier-triggered wind slabs occurred at treeline and below treeline.
Looking forward, we expect human-triggered wind slabs will remain possible, especially where new snow and wind are forming fresher, more reactive slabs. Consider the fact that these slabs have the potential to 'step down' to the facetted lower snowpack, resulting in larger avalanches.
We have very few eyes out there. If you do get out please consider reporting in the MIN.
Snowpack Summary
Overnight and throughout the day 5-10 cm of new is expected to be redistributed by westerly winds into fresh, reactive wind slabs in the alpine and treeline.
This snow overlies a heavily wind-affected surface in open areas. In the alpine, many slopes may have been stripped back to early-season layers or rock.
30-60cm of snow sits on top of a weak, sugary, faceted lower snowpack. Cold temperatures have weakened and faceted the snowpack as a whole. A rain crust sits near the ground.
Total snowpack depths at treeline elevations are 50-80 cm.
Weather Summary
Monday night
Cloudy with snowfall, up to 10 cm of accumulation expected. Westerly winds 30-60 km/h at ridgetop. Treeline temperatures drop to a low of -15 C.
Tuesday
Cloudy with snowfall, up to 5 cm of accumulation. Northwesterly winds 40-60 km/h at ridgetop. An alpine temperature inversion is possible, with valley bottom temperatures close to -20 C and alpine temperatures around -10 C.
WednesdayA mix of sun and cloud with some lingering snow flurries. Westerly winds 20-40 km/h at ridgetop. Treeline temperatures reach a high of -10 C.
ThursdayCloudy with snowfall, up to 5 cm of accumulation. Westerly winds 30-60 km/h at ridgetop. Treeline temperatures reach a high of -5 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
New snow and wind may form fresh, reactive slabs in lee areas in the alpine and treeline. Older, hard wind slabs may exist below the snow. These slabs may be more stubborn to trigger, but would result in larger avalanches. Avoid snow that feels drum like or hollow.
Small avalanches may trigger a bigger avalanche by 'stepping down' to the weak and faceted crystals buried deeper within the snowpack.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
The lower snowpack is composed of weak, sugary facets. Avalanches on this layer are possible where a cohesive slab (as opposed to loose, powdery snow) exists above these facets. Keep in mind that smaller wind slab avalanches also have the potential to 'step down' to this layer, resulting in large avalanches.
Observations on this layer are currently limited. In times of uncertainty such as this, our best defense is to keep terrain choices conservative and reduce your exposure to avalanche terrain where possible.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 6th, 2022 4:00PM
