Avalanche Forecast
Issued: Dec 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
Grant Statham,
The danger continues to come down following the last storm, but we expect windslabs remain in high alpine areas (where we have no observations). Cold temperatures, light winds and soft surface snow have created excellent backcountry conditions.
Summary
Weather Forecast
A Pacific weather system moves into the region this evening and will deposit 5-10 cm along with moderate S winds and temperatures remaining in the -5 to -15 range. This storm will clear by late day on Tuesday when a ridge of high pressure clears the skies for mid-week.
Snowpack Summary
20-30 cm of low density snow surface snow is bonding well with only limited windslab development at treeline and the low alpine. Our concern is growing for weaknesses developing above the Dec 2 rain crust, now buried 60-80 cm at treeline elevations (below 2250). Watch carefully as this weakness develops into an avalanche problem in the coming days.
Avalanche Summary
No new natural avalanches have been reported. Both LL and SSV ski areas report windslabs up to size 1 in their alpine areas. SSV noted several avalanches up to size 2 failing on the Dec 2 layer and propagating up to 40 meters wide by 70 cm deep fractures - these are the first avalanches we have seen on the Dec 2 layer.
Confidence
Problems
Wind Slabs
We suspect this problem exists in the high alpine, where we have no observations. Ski hills have been reporting minimal windslab action over the past 24-hours, but we expect they exist above 2500 meters in leeward areas.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
This layer has stabilized over the past few days and we have not seen an avalanche on it for over one week. The weakness remains and the problem is not gone, just sleeping for now. Continue to very wary of large alpine terrain features.
- Avoid steep convexities or areas with a thin or variable snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 14th, 2021 4:00PM
