Daytime heating and solar radiation will play a large role in the danger rating for the next few days.
Confidence
Good - Timing or intensity of solar radiation is uncertain
Weather Forecast
Overnight: Temperatures cooling down, nil precip., freezing level at valley bottom, light to moderate SW winds.Sunday: Sunny with some cloudy periods, nil precip., variable light winds. Freezing level around 900m.Monday: Sunny with some cloudy periods, nil precip., light winds, freezing level at valley bottom.Tuesday: Sunny with some cloudy periods, nil precip., light winds, freezing levels rise to around 1300m.
Avalanche Summary
1 size 2.5 snowmobile triggered avalanche in steep shallow snowpack, failing to near ground level. Areas of shallow snowpack are of special concern, as well as areas where there is a hazard from above such as cornices or steep south facing cliffs.
Snowpack Summary
Extensive wind transport and wind slab development has occurred in all areas of the region. Recent storm snow varies from 40-70 cm across the region and in some alpine areas storm slabs are more than a metre thick. Persistent weak layers of buried crusts/facets/surface hoar continue to be a concern, and may have been the failure plane for recent large natural avalanches. Forecast very warm temperatures may result in loose wet avalanches or cornice falls that may trigger the persistent weak layer at the base of the snow pack ( depth hoar ). Strong solar radiation combined with above freezing temperatures in the alpine could create very touchy triggering on Southerly aspects.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.