The persistent slab, hard windslabs and wind-affected snow conditions continue to be the story for the week as evidenced by Sunday's close call on Wolverine Ridge. The odd natural avalanche has occurred, but human triggering is likely on steep slopes.
Hard windslabs exist 15-30cm deep in alpine areas. They may be triggered on their own, but have been prone to stepping down to the persistent layer of facets near the ground.
A 20-60 cm slab sits over a persistent weak layer of basal facets, buried sun crusts, or isolated pockets of surface hoar. This layer is unpredictable and will be around for some time to come.
An explosive triggered a size 2 hard slab at Lake Louise, and a cornice fell and triggered a size 2 at Sunshine, both avalanches occurred in steep, alpine terrain. Yesterday a near-miss occurred in the Lake Louise backcountry with a persistent slab at treeline. Small sluffs of low-density surface snow should be expected in gullies.
The snowpack surface is generally wind-blasted in most places with a few cm of low-density new snow from the past 24 hours. This has produced hard windslabs that can fail with the right trigger in the right place. Any avalanche triggered now will likely step down 20-40 cm into the persistent layers and become larger.
An arctic ridge of high pressure over BC fights with a low-pressure system over Alberta, bringing cold temperatures and light snow for the next 24 hours. On Tuesday, expect 2-5 cm (more to the east), temperatures ranging from -10 to -15 and winds from the NW before a clearing trend for Wednesday.
More details can be found in the Mountain Weather Forecast.
