Recent snowfall with strong winds has produced new slabs at higher elevations. Expect avalanche activity to increase on southerly aspects if the sun comes out.
Weather Forecast
SUNDAY: A mix of sun and cloud, light westerly winds, alpine temperature -3 C, freezing level 1600 m.MONDAY: Mostly cloudy, light southwesterly winds, alpine temperature -3 C, freezing level 1600 m rising to 2000 m by late afternoon.TUESDAY: Mostly cloudy with afternoon precipitation, accumulation 10 mm, alpine temperature 0 C, freezing level 2600 m dropping to 2000 m.
Avalanche Summary
On Friday, numerous storm and wind slabs were reported in the region. They were generally small to large (size 1 to 2), triggered by skiers, explosives, cornice falls, and naturally, and 5 to 20 cm thick. Many loose wet avalanches were also observed at all elevation bands.On Wednesday, skiers triggered a large persistent slab in alpine terrain. It was reported as a size 3, 50-200 cm deep.
Snowpack Summary
Around 30 cm of recent snow and strong southerly winds have created new slabs at higher elevations. This snow overlies various old surfaces including previous storm snow, melt freeze crusts on sunny aspects, and old wind slabs. On ridges, cornices are reported to be large and fragile. At lower elevations, precipitation fell as rain and creating wet snow conditions.A weak layer consisting of surface hoar, facets, or a sun crust from late March is now buried about 60 to 90 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on shady aspects between 1900 m and 2250 m.Below this, the snowpack is well-settled and strong.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.