Wind slabs are sensitive to human triggering and some natural activity has been occurring. We sound like a broken record, but this is a year to stick to low-angle slopes and limit exposure to overhead terrain.
Recent variable strong winds have created and added to previous windslabs that formed in Alpine and Treeline areas. In addition, there are several iterations of buried wind slabs formed in previous wind events down 30 to 50cm in the snowpack.
The alpine is still variable in total amounts of snow but the basal layers haven't changed. The entire lower half is either facets, or depth hoar. Thin weak areas should be treated as suspect and avoided.
One size 2 naturally triggered slab avalanche was observed on Mt Rundle in a steep alpine bowl on a NE aspect. This avalanche appeared to fail in the deep persistent weak layer of basal facets. On Friday a size 2 avalanche was observed in the Buller Mountain area that was triggered by a cornice collapse.
Up to 35cm of recent storm snow has been blown into wind slabs at treeline and above. Sheltered areas may have some soft snow on the surface giving decent skiing. Easy shears persist down 25 to 35cm and have have seen some reactivity to skier traffic. Moderate shears have also been found down 30 to 50cm on various versions of old wind slab interfaces. The midpack is strong in deeper snowpack regions near the divide, but the basal facets/depth hoar persist. An avalanche initiated in the upper snowpack could easily step down to the deep persistent weak layers, causing a very large avalanche. This season it is important to always have full depth avalanches on your mind.
Very light flurries through Saturday will likely only amount to 2cm by Sunday morning. Temperatures will range between -20 and -13 with clearing skies later in the day. Winds will be moderate from the SE.
More details can be found in the Mountain Weather Forecast.
