We are in a low probability high consequence situation. Natural activity has subsided but any slope that did not slide should be treated with utmost caution. Be vigilant if the sun comes out which could destabilize the snow rapidly.
Weather Forecast
Saturday to Monday will be -3 to -12, clouds and flurries, 5cm of snow, and light to moderate SW winds. Sunday may be more sun than clouds.
Snowpack Summary
Large looming cornices are present. Wind, persistent, and deep basal slabs found at and above treeline. Mid-pack has several weaknesses yet is providing bridging strength above the weak base. Basal layer is facets and depth hoar, with a rain crust from November. On southerly slopes a melt freezing crust is developing as the pack warms.
Avalanche Summary
No patrol on Friday and nothing new reported. Thursday several fresh slab avalanches were recorded at treeline and alpine. Such as a class 3 triggered by a falling chunk of cornice on a NE facing slope, a size 2 from a S facing slope likely triggered by solar radiation, and a skier may have triggered a size 2 on a N slope near Boundary lake.
Confidence
Timing or intensity of solar radiation is uncertain
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.
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.