Avalanche Forecast
Regions:
Give large and/or steep slopes a wide berth. New snow will take time to settle, and wind will continue to keep hazard elevated. Watch for signs of instability like cracking in the new snow and assume that a small avalanche could trigger larger slopes and deeper layers.
Confidence
Moderate
Avalanche Summary
On Friday our field team witnessed a wide spread natural avalanche cycle on all aspects in the alpine and tree line up to size 3 with the most impressive propagation in large connected cross-loaded and lee features . Natural activity could continue into the weekend but the bond will improve over time. Human triggering will remain possible given the amount of new snow and what it is resting on.
Snowpack Summary
Thursday's substantial storm dropped upwards of 50 cm of snow around the Haines Pass with rain falling on top of the snow up to 700m, amounts tapered as you move inland, which has once again become a scoured area with only soft snow in sheltered gullies and side valleys.
Southerly wind accompanied the storm, and continued into Friday meaning deeper deposits may exist in lee terrain features near ridges. All this snow overlies previously wind affected snow (sastrugi) in wind affected areas and faceted snow in sheltered features. The new snow has not bonded well to these previous surfaces.
The storm snow is also loading a buried weak layer of surface hoar found about 80 cm to 200 cm around around Haines pass. This layer is most prominent on northerly slopes sheltered from the wind. On other aspects, this layer is a hard melt-freeze crust with weak facets around it. To date this layer is has been most problematic in alpine terrain.
The remainder of the middle of the snowpack is consolidated and strong. Weak faceted grains are found near the base of the snowpack and a thick melt freeze crust is next to the ground up to 20cm thick.
Weather Summary
Friday Night
Cloudy, with moderate to strong southerly winds. Freezing levels drop to valley bottom. Up to 5 cm of snow overnight.
Saturday
Partly clear skies with moderate to strong southeast winds. Freezing levels reach 800 m, alpine high temperatures of -7 °C.
Sunday
Cloudy with light southeast winds. Up to 5 cm of snow. Freezing levels reach 700 m, alpine high temperatures of -8 °C.
Monday
Cloudy to start with clearing skies in the afternoon. 5 cm possible over Sunday night, easing in the morning. Light southerly winds. Freezing levels around 500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Be aware of the potential for large, deep avalanches to run full path or even longer.
- Don't let the desire for deep powder pull you into high consequence terrain.
Avalanche Problems
Storm Slabs
A substantial storm impacted the region on Thursday, storm and wind slabs rapidly formed and have not bonded well with previous surfaces. Human triggering will remain possible into the weekend.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely - Very Likely
Expected Size: 1 - 2.5
Persistent Slabs
The new snow is loading a weak layer of surface hoar and/or faceted grains around a hard crust, which increases the likelihood of triggering an avalanche on this layer. The layer is buried around 80-200 cm and has previously produced widely propagating avalanches in alpine terrain and it is capable of being remotely triggered from a distance. The most likely area for riders to trigger it is in wind-sheltered, north-facing terrain, and in rocky terrain where the snowpack is thin.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Possible - Likely
Expected Size: 2 - 3