Strong solar radiation is expected throughout the weekend. When solar radiation is strongest, the avalanche danger may exceed posted levels.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Sunday: Clear skies - very light southwest winds - freezing level at 1700m Monday: Increased cloud with the possibility of very light snowfall - light southwest winds - freezing level at 1500m Tuesday: Trace amounts of snowfall with possible clearing in the afternoon - moderate southwest winds - freezing level at 1500m
Avalanche Summary
A size 2.5 natural slab avalanche was observed on a north aspect at 2300m. Details of the weak layer are uncertain. A size 2 natural avalanche was also observed having reacted on a crust on a southeast facing slope at 2000m. Solar warming is of particular concern this weekend, as it could destabilize surface snow and cornices, potentially initiating deep failures on the mid-February layer. Be particularly wary of sunny aspects during the heat of the day.
Snowpack Summary
Recently formed wind slabs exist in the alpine and at treeline. Solar radiation has led to moist surfaces on sun exposed slopes with good crust recovery developing at night. Cornices have grown large and unstable. A consolidated deep slab overlies weak surfaces that formed in early February. Now 1-2 m below the surface, these weaknesses include surface hoar, facets or crusts. Operators continue to express concern about the potential for deep releases on these interfaces.
Problems
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.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.