The recent storm snow may take some time to bond and the weak layers will likely need time to strengthen. Conservative route-selection is suggested.
Weather Forecast
SATURDAY NIGHT: Mainly cloudy with isolated flurries, moderate southwest winds, alpine temperature -4 CSUNDAY: Cloudy with isolated flurries, moderate southwest winds, alpine temperature -3 C, freezing level 1200 m.MONDAY: Mix of sun and cloud, light to moderate west winds, alpine temperature -10 CTUESDAY: Cloudy with sunny breaks, light southwest winds, alpine temperature -6 C
Avalanche Summary
Evidence of a widespread natural avalanche cycle was observed on Friday. Storm slabs were reactive to skier traffic and explosives, producing large (size 2 to 3) avalanches with depths around 40 cm. A couple avalanches were observed on the deeper layers described in the snowpack summary.
Snowpack Summary
The recent storm dropped variable snowfall amounts across the region. In the north, upwards of 100 cm of snow fell. In the remainder of the region, around 40 to 60 cm of snow accumulated. The snow fell with strong westerly winds, so the deepest and touchiest deposits will likely be in lee terrain features. The freezing level rose to around 1500 m on Friday, so expect to find wet snow or a frozen crust below this elevation.All this snow is loading a weak layer that formed during the dry spell in early December. It is around 80 to 120 cm deep. The layer is composed of weak and sugary faceted snow, feathery surface hoar crystals, and on south aspects also a sun crust. The base of the snowpack is composed of weak faceted snow at alpine and treeline elevations. These basal weak layers have been producing large avalanches as recently as December 31. Human triggering any of these layers is most likely on slopes that didn't previously avalanche and on slopes that have variable snowpack depth, such as rocky alpine features.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.