Minimize exposure to slopes with large cornices overhead when it is cool and cloudy and completely avoid them if it is warm and/or sunny.
Weather Forecast
MONDAY: Cloudy with isolated flurries. Light southwesterly ridgetop winds. Freezing level around 2000m.TUESDAY: Cloudy with flurries. Light to moderate southerly ridgetop winds. Freezing level around 1800m.WEDNESDAY: Mix of sun and cloud. Light to moderate southwesterly ridgetop winds. Freezing level rising to around 2100 m.NOTE: The convective flurries which are common during this time of year can result in widely varying snowfall amounts throughout a region. These spring squalls routinely drop 20+ cm of snow in one valley while the adjacent drainage remains dry. For this reason, the distribution of avalanche problems associated with new snow, such as wind slabs, can vary greatly within a region.
Avalanche Summary
On Saturday, several natural and skier triggered wind slabs up to size 2 were reported on steep lee features at Treeline and above. Falling cornices triggering large avalanches is currently our primary concern.
Snowpack Summary
Triggering large avalanches on facets near the bottom of the snowpack is currently our primary concern. On high north facing terrain which is currently where the best skiing can be found, the problem is the possibility that if a large cornice falls on a steep slope, it will trigger this layer. On solar aspects, the problem is small loose wet or wind slab avalanches stepping down to this layer or skier triggering the layer by hitting a shallow spot in a large, steep, and rocky alpine face. Additionally, lingering wind slabs formed by recent snow and wind on lee features at Treeline and above continue to be reactive to human triggers.
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.
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.