New snow, strong winds and a weak base are creating ideal conditions for wind slabs. Natural activity is slowing but conditions remain touchy for skier triggered avalanches.
Weather Forecast
Light snowfalls with moderate to strong SW winds will continue over the next few days. Temperatures will remain above seasonal in the -5C range.
Avalanche Summary
A few new avalanches up to sz 2.5 were observed in Alpine terrain on Saturday. These slabs were mainly failing at the interface of the recent storm snow on N and E aspects.
Snowpack Summary
An additional 4cm fell overnight on friday and 10cm during the day on Saturday. Over the past 5 days 46cm of snow has fallen at treeline with warm temps and strong SW winds. Widespread windslabs have developed and we have seen lots of cracking, reports of whumpfing, and skier controlled avalanches on the Dec 10th surface hoar and facet interface down 40-60cm. Recent natural avalanche have stepped down to the Oct crust with fracture depths over 1m. The new windslabs and persistent slabs will take a few days to settle out and strenghten.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.