Avalanche Forecast
Issued: Nov 30th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
jpercival,
Avalanche Canada
Very dangerous avalanche conditions. Travel in avalanche terrain is not recommended. Numerous reports of skier-triggered, natural, and remote trigger avalanche observations. More snow is forecast and this will add to the potential for larger avalanches to occur.
Summary
Confidence
Moderate
Avalanche Summary
Many new natural and human-triggered avalanches have been reported in the alpine and at the treeline, between 1700 and 2200 m. The common theme is that they are failing on the November 21st / surface hoar facet crust interface.
Additionally, the terrain where these avalanches occurred was steep and focused on north through to east-facing terrain. The size of these avalanches has been from size 1 (small) to size 3 (very large).
One avalanche, in particular, was remotely triggered by a skier and began as a size one and picked up enough mass to strip the snowpack to the ground resulting in a size 2.5 (large) avalanche. Temperatures are forecast to remain cool and I would surmise that this slab avalanche problem will continue to persist.
On the southern border of this region, another remote trigger avalanche was observed at 2080 m. This avalanche size 1.5 (small) failed on the Nov 21 surface hoar/ facets interface and had noted surprising propagation.
Snowpack Summary
A new snowfall Tuesday night that varies between 5 and 15 cm of new snow has been reported at numerous operations. A series of storms over the past week has delivered 30 to 50 cm of new snow. This snow fell during a period of cooling and is light and easily transported by the wind.
A layer that was buried November 21st can be found down 60 to 90 cm and is primarily a mix of surface hoar and faceted crystals. This layer is the primary concern of persistence and has been the key component of the recent natural avalanche cycle.
The average snowpack depth below the treeline is 40 to 70 cm and above that elevation is 100 to 150 cm, with wind-loaded areas presenting as 200 cm.
Weather Summary
Wednesday Night
Cloudy with snowfall, accumulation 5 to 10 cm, 20 km/h southwest wind, treeline temperature -10 to -18 °C.
Thursday
Clearing sky with some possible isolated afternoon flurries, accumulation 1 to 3 cm, 10 km/h southwest wind, treeline temperature -15 to -20 °C.
FridayClear sky no forecast precipitation, 20 km/h northwest wind, treeline temperature -10 to -15 °C.
SaturdayClear sky no forecast precipitation, 20 km/h northwest wind, treeline temperature -10 to -15 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Travel in alpine terrain is not recommended.
- Make observations and assess conditions continually as you travel.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
Problems
Persistent Slabs
Human trigger avalanches are very likely on this slab problem. Around 40 to 80 cm of snow from the past week is forming a slab that is not bonding well to the underlying snowpack. The interface of concern formed during mid-November and is composed of faceted grains, surface hoar, and a hard crust. To date the layer has been most problematic above 1700 m.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
This avalanche problem will be found on north aspect terrain in the alpine and at treeline. These avalanches will be localized to zones just below ridge tops and adjacent to flat areas that transition into steeps ( Convex slope ) . Reports suggest that this avalanche problem when triggered will likely create enough mass to step down to the Nov 21st layer enhancing the potential for a very large avalanche to occur.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 1st, 2022 4:00PM
