Flights today along the 93N found several instances of small windslabs triggered by skiers that appeared to have stepped down to the deep persistent layer.
Weather Forecast
One more night of cold temperatures reaching -20C in valley bottoms with an inversion allowing temps near -10C at 2000m. A Pacific trough will push the current ridge out of the way Sunday bringing cloud and a warming trend that will break down the inversion. Up to 5cm of snow is possible on Monday and another 10cm is possible overnight Tuesday.
Snowpack Summary
No new snow in several days. Old wind slabs 10-40cm deep linger in immediate lee areas of the alpine. The October 26th crust/facet layer is ~30 cm above ground. In many areas the entire snowpack is faceting and becoming quite weak. Snow depths range from 50-85 cm at 2000 m.
Avalanche Summary
Another skier accidental today on the SE slopes of Cirque Fore-Peak at 2700m above Helen Lake. Two skiers were caught on the flanks of a slab 20-40cm deep, 80m wide, running up to 250m with no burial but some lost equipment. This slab was certainly originated as a windslab in the immediate lee of the ridge but definitely scrubbed down to facets
Confidence
Intensity of incoming weather systems is uncertain on Tuesday
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.