The recent snow is touchy to human triggers, especially where the snow has formed more of a slab above the weak interface of well-preserved surface hoar crystals and crusts.
Weather Forecast
Thursday: Mostly cloudy with moderate westerly ridgetop winds. Alpine temperatures near -4 and freezing levels rising to 1000 m.Friday: Cloudy with isolated flurries and gusty northwest ridgetop winds. Alpine temperatures high of -2 and freezing levels 1300 m. Saturday: Mix of sun and cloud with strong northwest ridgetop winds. Alpine temperatures high of -1 and freezing levels rising to 2000 m.
Avalanche Summary
On Tuesday, a few storm slabs were reported up to size 1 from NE-W aspects between 1300 m and 1500 m. Reports indicated that the storm slabs were touchier where there was some wind effect creating a more cohesive slab.
Snowpack Summary
15-30 cm of snow sits above a layer of large surface hoar crystals and sun crust. In areas that have had wind effect the recent snow has been settling into a thin but reactive slab above this weak layer, with enhanced reactivity noted at elevations between 1500-1800 metres. In sheltered areas the snow is faceting and lacks cohesion above this layer which is only reactive as dry loose sluffing. Forecast warmer temperatures will likely change this and promote increased slab properties this weekend. Strong winds associated with the new snow formed reactive wind slabs on leeward slopes at upper elevations. The middle and lower portions of the snowpack are generally well-settled and strong.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.