Wind slabs have been reactive this week and they may remain sensitive to human triggering Friday. Be mindful of the potential for wind slab avalanches to step down to deeper weak layers.
Wind slabs may be found on all aspects in exposed terrain due to shifting winds. These slabs have been reactive to riders and may continue to be reactive particularly in steep convex alpine terrain.
A couple problematic layers may be found around 50 to 100 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust.
Thursday night: Increasing cloud, moderate to strong southwest wind, freezing level 600 m.
Friday: 5-10 cm new snow, wind easing moderate to light southwest, alpine temperature -4 C, freezing level 900 m.
Saturday: 5-10 cm new snow, wind increasing to strong southwest, alpine temperature -5 C, freezing level 900 m.
Sunday: Clearing, light to moderate southwest wind, alpine temperature -2 C, freezing level 1500 m.
Numerous wind slab avalanches were reported Tuesday, triggered naturally and by riders at treeline and alpine elevations. Most occurred on wind loaded southerly aspects due to recent northerly wind. Check out these MINs for a few examples: here, here, and here.
A few large avalanches have been observed on the weak layers described in the snowpack summary within the past week and they were triggered triggered by riders, explosives, and naturally. They occurred on northerly aspects between 1900 and 2100 m and were generally 30 to 50 cm deep.
5-10 cm of new snow is forecast to fall through the day Friday. The new snow falls over hard wind slabs and wind scoured surfaces in exposed terrain, and a melt-freeze crust on solar aspects at upper elevations.
Two potential concerning weak layers may be present in the snowpack:
To date we have mostly seen sporadic avalanche activity on these layers, but they remain possible to trigger where they exist in the mountains.
The remainder of the snowpack is well-settled.
