Snow is forecasted for Saturday with associated strong winds. Be cautious of periods of rapid precipitation or wind loading, as avalanche activity may increase.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
SATURDAY: Cloudy with snowfall, accumulation 10 to 20 cm, strong southerly winds, alpine temperature -3 C, freezing level 1600 m.SUNDAY: Mostly cloudy with light snowfall, accumulation 2 to 5 cm, 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.
Avalanche Summary
On Thursday, small loose dry, loose wet, and storm slab avalanches were reactive to skier triggers.On Wednesday, skiers triggered a large persistent slab in alpine terrain. It was reported as a size 3, 50-200 cm deep.
Snowpack Summary
New snow and strong southerly winds are creating 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 is falling 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.