Avalanche Forecast
Issued: Dec 21st, 2021 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
Dnylen,
Avalanche Canada
New snow and wind have formed fresh windslabs. Avoid wind loaded terrain which will appear deep and styrofoam-like. Small avalanches in motion may be able to trigger large avalanches. Limit exposure to overhead avalanche terrain.
Summary
Confidence
Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.
Weather Forecast
Winds increasing overnight and remaining strong from the north accompanied by cold temperatures.
TUESDAY NIGHT: Overnight low temperature around -10, moderate to strong north/ northeast wind. No new snow expected.
WEDNESDAY: Mostly clear, daytime high temperature around -12, strong north/northwest wind, no snow expected.
THURSDAY: Broken cloud cover, daytime high temperature around -21, moderate to strong north/northwest wind, possible 2 cm of snow.
FRIDAY: Broken cloud cover, daytime high temperature around -27, moderate north wind, no snow expected.
Avalanche Summary
We expect a natural avalanche cycle is happening, and we will be on the lookout for evidence of this during the week ahead.
  This MIN from Saturday shows a small wind slab in a terrain feature known for producing these kinds of avalanches. We expect more of them are happening during this recent storm.
On December 1, a size 2.5 avalanche was remotely triggered by a recreational group on Log Cabin. This avalanche likely failed on the weak, sugary snow at the bottom of the snowpack.Â
Snowpack Summary
10cm of new snow is now being blown around by strong north winds. All of it will come to rest on a variety of old snow surfaces. Like wind pressed sastrugi in the alpine, and some low density snow in sheltered treed areas.
On the weekend two MIN reports here & here talked about some surface hoar at and below 1300m and we'll be looking for it over the next few days.
The middle snowpack is supportive to travel but snow depth still varies greatly with aspect and elevation.Â
The lower snowpack is made of weak sugary snow. An avalanche at this interface is most likely to be triggered in shallow areas or with a large impact like a cornice fall or surface avalanche.
Terrain and Travel
- Wind slabs are most reactive during their formation.
- Be aware of highly variable recent wind loading patterns.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
10cm of new snow is being formed into windslabs by ongoing north winds. At and below 1300m these may be sitting on buried surface hoar which could result in larger than expected avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
This layer is deeply buried and there has been very little activity on it since December 1st.
Most likely trigger points are areas where the snowpack goes from thin to thick, such as rock outcroppings. A large trigger like a cornice fall or avalanche in motion could potentially activate this deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 22nd, 2021 3:00PM
