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 is advised.
Summary
Confidence
Avalanche Summary
Explosive control on Sunday produced several small (size 1-1.5) persistent slab avalanches from North and Northwest facing treeline. These avalanches failed on the Mid-November surface hoar layer.
On Saturday, a small (size 1) skier triggered persistent slab avalanche occurred on a northwest aspect at treeline. A larger (size 2) natural slab avalanche was also observed from a distance on an east-facing alpine slope.
Last week, a small (size 1) natural persistent slab avalanche was observed at treeline on a steep, south-facing road bank. It failed on the sugary, faceted layer 25 cm deep.
We have very few eyes out there. If you do get out please consider reporting in the MIN.
Snowpack Summary
New snow and westerly winds may form fresh wind slabs in the alpine and treeline throughout the day. The upper snowpack has been redistributed by variable winds in the past week. In exposed terrain, slopes may have been scoured back significantly. In sheltered areas, 20-60 cm overlies a generally weak, sugary, facetted lower snowpack. A buried layer of surface hoar sits 25-60 cm deep and remains a layer of concern.
The overall height of snow is highly variable throughout the region with around 40-150 cm in the alpine.
Weather Summary
Monday night
Cloudy with light snowfall, less than 5 cm of accumulation expected. Westerly winds 25-40 km/h at ridgetop. Treeline temperatures drop to -16 C.
Tuesday
Cloudy with continued snowfall, up to 5 cm of accumulation expected. Westerly winds 25-40 km/h at ridgetop. An alpine temperature inversion may be present, with alpine temperatures around -10 C and valley bottom temperatures close to -15 C.
WednesdayCloudy with light snowfall, less than 5 cm of accumulation. Westerly winds 20-30 km/h at ridgetop. Treeline temperatures reach a daytime high of -10 C.
ThursdayCloudy with snowfall, up to 5 cm of accumulation is possible. Southwesterly winds 30-60 km/h at ridgetop. Treeline temperatures reach a daytime high of -8 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.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.
Problems
Wind Slabs
Westerly winds may redistribute any loose, powdery surface snow into fresh and reactive wind slabs in the alpine and open areas at treeline.
These slabs likely overlay a weak, sugary lower snowpack. If triggered, small avalanches may trigger a bigger avalanche by 'stepping down' to these weak and faceted crystals.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Buried layers of surface hoar and facets have been reactive to human triggering in recent days. The most reactivity has been observed in shaded areas at treeline, where surface hoar may be preserved, and in wind loaded areas at upper elevations, where a cohesive slab has been formed.
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
