Avalanche Forecast
Issued: Nov 29th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Fresh storm slabs are expected to be most reactive in wind loaded lees at upper elevations, and where new snow falls on a melt freeze crust on south aspects or surface hoar in very wind-sheltered areas around treeline.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations.
Weather Forecast
Sunday night: 5-10 cm new snow. Moderate to strong southwest wind, freezing level 1000 to 1300 m.
Monday: 5-10 cm new snow. Moderate southwest wind, freezing level 1100 m.
Tuesday: Clear, light northwest wind, freezing level 700 m.
Wednesday: Clear, light southerly wind, freezing level 1000 m with an above freezing layer 1500 to 3500 m.
Avalanche Summary
Monday we're expecting storm snow avalanches size 1-1.5 especially in lee features where wind is depositing fatter pockets of snow, or on south aspects where the new snow may be falling on a thin melt-freeze crust.
The most recent report of an avalanche on the early-November layer was from November 21 near Duffey Lake. Check out this MIN for a photo.
Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!
Snowpack Summary
10-20 cm of new snow falls ontop of wind affected surfaces in the alpine, a thin melt-freeze crust on south aspects, and possibly surface hoar in wind sheltered areas around treeline (observed in the Coquihalla area). Moderate to strong southwest winds will likely load the falling snow into pockets of potentially reactive storm slab in lee features at upper elevations.
The lower snowpack is characterized by a few crusts formed during warm periods over the last month.Â
- In the north, treeline snowpack depth sits around 80 to 120 cm. The crust of note here is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. Snowpack tests and recent avalanche activity suggest that this layer could be triggered by humans and produce large avalanches.
- In the south of the region, the snow line has been reported around 700 m near Hope and treeline snowpack depth sits around 100-150 cm. The deeper crusts in this area are generally well bonded to surrounding snow.
Terrain and Travel
- Watch for fresh storm slabs building throughout the day.
- Avoid freshly wind loaded terrain features.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
New snow and wind are forming storm slabs which we are expecting to be especially reactive:
- in lee features where wind is depositing fatter pockets of snow
- on south aspects where the new snow may be falling on a thin melt-freeze crust
- in very wind sheltered areas around treeline where new snow may be falling on surface hoar
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
In the north of the region (e.g., Duffey Lake), there is potential to trigger a weak layer of sugary faceted grains around a hard melt-freeze crust near the base of the snowpack. Although we haven't seen avalanches on this layer since last weekend, the most likely terrain features of concern are where the ground cover is smooth, such as on scree slopes, rock slabs, or glacial ice.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Nov 30th, 2020 4:00PM
