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
Saturday: Clear skies with strong solar input - light southwest ridge top winds - freezing level at 1500m Sunday: Clear skies with strong solar input - light to moderate southwest ridge top winds - freezing level at 1700m Monday: Possible increased cloud - light and variable winds - freezing level at 1700m
Avalanche Summary
On Thursday a size 3 natural storm slab released on a southeasterly alpine slope. A melt freeze crust that formed earlier in the week was the suspected bed surface. A size 2 on a similar feature was also reported.The most recent report of avalanche activity on the early-February layer was Monday where natural avalanches up to size 3.5 failed on southerly aspects down about 100-150cm. Avalanches releasing on this layer are becoming less frequent; however, solar warming is of particular concern over the next few days, as it could destabilize storm slabs 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
20-30 cm recent storm snow overlies various surfaces including settled snow, wind slabs and crusts. New wind slabs have formed in the alpine and at treeline. Solar warming last weekend left a melt-freeze crust up to about 2400 m on solar aspects and up to about 1500 m on all aspects. 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
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.
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.