Avalanche Forecast
Issued: Dec 26th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
dsaly,
Avalanche Canada
Watch for more reactive deposits in areas influenced by the wind. Be ready for the cold.
Summary
Confidence
Weather Forecast
Sunday night: Cold with isolated flurries, 5 cm. Moderate decreasing east wind. Overnight temperature dropping below -27.
Monday: Cold and cloudy, with sunny breaks. Light west wind increasing to moderate through the day. Cold temperatures with a high of -21.
Tuesday: Cold, mostly cloudy, and isolated flurries. Light southwest wind and a high temperature of -20.
Wednesday: Cold, with a sun and cloud mix. Light east wind and a high temperature of -24.
Avalanche Summary
Evidence of a natural avalanche cycle was observed Saturday morning, including a large (size 2.5) natural storm slab avalanche which ran 900 m. Explosives also triggered storm slab avalanches size 1.5-2, noting that although low density slabs, fast moving snow was running far and entraining a lot of snow.
On Friday, 3 large (size 2-2.5) natural slab avalanches were reported, all failed on a persistent weak layer 100-200 cm deep, likely triggered by the new load of snow. Explosives also triggered large (size 2.5) storm slabs.
On Thursday, skiers and machines triggered storm slab avalanches to size 2, explosives triggered slab avalanches to size 3. Poor visibility prevented good alpine observations.
Snowpack Summary
Recent storm totals reached over 100 cm! Cold temperatures and calm wind will keep snow light and fluffy, but snow will be redistributed easily with any wind. Reports also indicate the recent snow buried a surface hoar interface and pockets of old wind slab. For now, we don't expect the new snow to bond well to the old interface. Sluffing is to be expected in steep terrain.
A crust from early December is now 90-150 cm below the surface, and is found up to 2400 m. A layer of weak facets (sugary snow) has been reported above and below this crust. This is the layer of concern in our persistent avalanche problem, recent snowpack tests are generally showing hard results on this interface.
The lower snowpack consists of a variety of early-season crusts and mainly moist snow. Snowpack depths range from 100-250 cm at treeline elevations and taper quickly below 1800 m.
Terrain and Travel
- Start with conservative lines and watch for clues of instability.
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Wind Slabs
Recent winds have been north and easterly, be mindful of reverse loaded features. Watch your sluff, loose-dry snow may easily initiate in steep terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 100-150 cm over a crust from early December. Large natural avalanches avalanches failing on this layer have been reported as recently as Friday, Dec 24. Additionally, some operators have reported that re-loaded bed surfaces (areas that have already avalanched this season) have become reactive with new loads, while deeper snowpack areas that did not previously avalanche remain dormant, furthering the complexity of dealing with a persistent weak layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 27th, 2021 4:00PM
