Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
MONDAY: Light precipitation in the afternoon combined with colder temperatures and light west winds. TUESDAY: Cold temperatures with light flurries. Winds light to moderate from the west. WEDNESDAY: Cold and clear.
Avalanche Summary
Recent reports indicate loose snow avalanches triggering very easily in steep unsupported terrain on all aspects. Some these avalanches were stepping triggering some of the weaknesses deeper in the snowpack to size 2. On Friday a rider triggered size 2.5 cornice failure on a northeast aspect stepping down to ground in a thin snowpack area. This cornice pulled back to the ridge line.
Snowpack Summary
20-40 cm of low density new snow combined with wind has encouraged additional slab development and cornice growth. This new snow now sits on a variety of surfaces (facets, surface hoar in sheltered areas, wind crust, soft slabs and hard slabs).Avalanche professionals are gaining confidence in the mid-December persistent weakness, now down 110-190cm, but concern remains for heavy triggers, such as cornice drops on steep unsupported slopes. When this persistent weaknesses is combined with weak wind slabs, thin trigger points, and a variety of other buried weaknesses the result is a highly variable snowpack with the potential for step-down deep slab avalanches.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.