The key weather factors to keep your eye on this weekend will be the sunshine accompanied by rising freezing levels. Solar radiation is a common trigger for cornices which is currently our primary concern.
Weather Forecast
SATURDAY: Mix of sun and cloud. Light westerly ridgetop winds. Freezing level around 1500m.SUNDAY: Sunny. Light southwesterly ridgetop winds. Freezing level rising to around 1800m.MONDAY: Mix of sun and cloud. Light southwesterly ridgetop winds. Freezing level hovering around 1700m.
Avalanche Summary
Two size 3.5 deep persistent slab avalanches were reported on Wednesday with crowns up to 4 metres deep. One was triggerd by a cornice and the other by solar radiation. The key weather factor to keep your eye on this weekend will be the sunshine accompanied by rising freezing levels. Solar radiation is a common trigger for cornices which is currently our primary concern.
Snowpack Summary
Recent snow and wind have formed wind slabs in the alpine on a variety of aspects caused by shifting wind directions. Cornices are large, looming, and the primary concern due to their potential to trigger large avalanches failing on facets at the bottom of the snowpack.
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.