Avalanche Forecast
Regions: Glacier.
The huge avalanches this week have been a reminder that, deep in our snowpack, lives the Dec 1 layer. It will take a large trigger to get it moving, but that can be done with cornices, slabs, etc.
A conservative frame of mind is good this winter.
Weather Forecast
Fairly benign weather the next few days, with another alpine inversion slated to arrive Thurs
Tonight: cloudy, Alp low -8*C, light winds
Tues: cloudy, Alp high -7*C, light winds
Wed: sun and cloud, Alp high -8*C, light W winds
Thurs: sun and cloud, Alp high -2*C with temp inversion in valleys, light SW winds
Snowpack Summary
Up to 35cm of recent snow now buries the Jan 20th (2-4mm) surface hoar. The Jan 11 (2-5mm) surface hoar is down ~70-90cm. The Dec 1 crust/facet combo is down ~1.5 - 2.5m. Widespread wind affect at treeline and above with pockets of wind slab.
Avalanche Summary
Limited avy activity observed Monday. Control work on Sunday produced results up to sz 3, one of which stepped down to the Dec 1st layer. Skiers were triggering small wind slabs up to size 1.5 on steep rolls.
Avy Control on Saturday, just West of the Park produced several sz 4 - 4.5 avalanches, extending historical trim lines through mature timber.
Confidence
Avalanche Problems
Wind Slabs
Moderate to strong winds on Sunday formed wind slab in the Alpine and down into treeline. These slabs may have buried surface hoar or a preserved stellar layer and could be sensitive to human triggering.
- Convex features and steep unsupported slopes will be most prone to triggering.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2.5
Persistent Slabs
Several persistent weak layers (see snowpack summary) in the upper 1m have been recently active, and in some instances, have stepped down to the deeper Dec 1 crust/facet layer. Investigate the snowpack before committing to your line.
- Be wary of slopes that did not previously avalanche
- If triggered the persistent slabs may step down to deeper layers resulting in very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1.5 - 3
Deep Persistent Slabs
The Dec 1 crust/facet combo woke up this past week, spitting out very large avalanches and knocking out mature timber in skiable terrain. This crust lives between 1700-2300m throughout the park, and will need a large trigger (cornice, slab, etc).
- Avoid thin, rocky or unsupported slopes.
- Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Unlikely
Expected Size: 2 - 4