Climbers be mindful of terrain overhead and avoid gullied features. There have been several natural & explosive triggered avalanches over the past few days... with more wind and snow on the way Thursday.
Increased wind Thursday will transport recent snow (10-25 cms) adding to the previous windslabs in alpine and treeline terrain. In some areas, these have been enough to initiate deeper layers in the snowpack once triggered.
This problem represents both the Dec. 2nd crust/ facet layer (treeline and below) and layers of faceted snow that were formed during the late December cold snap (all elevations). If triggered, either layer will result in large avalanches.
Wind on Thursday may trigger loose avalanches that may then entrain facets in the track and gain mass. Avoid climbing in gullied features with overhead hazard.
Winds increase Wednesday night with snow beginning on Thursday. 5-10 cms of snow is expected with strong W alpine winds and warming temperatures through the day. Friday looks to be overcast with moderate NW winds and light snow.
10-15 cms of low density snow with little wind effect sits on top of windslabs in the alpine and in some treeline areas.These overlie facets in many places resulting in wide propagations in recent avalanches. . The Dec. 2 crust/facets are ~130 cm deep in thicker parts, and half that depth in thinner snowpack areas such as Mt. Stephen and Mt.Dennis.
In the past 48 hrs a small avalanche cycle to size 2 occurred. Avalanche control in Yoho today produced slabs with every shot. Most were failing on a windslab or facet layer 40-60cm deep and then entraining facets in the track. One stepped down to the November facets ~ 180 cm deep.
