The region will be under the influence of a major warm-up through the weekend. Be aware of snow conditions changing quickly and avalanche danger rising.
Weather Forecast
Spring-like conditions persist through the weekend with clear, sunny and very warm temperatures during the day. Some cooling will exist overnight. Alpine temperatures are expected to reach above zero degrees and little wind is forecast.Friday: Few clouds. Alpine temperatures reaching 4.0 degrees. Freezing levels rising to 2300 m in the afternoon then dropping 1000 m overnight. Ridgetop winds will blow light from the West.Saturday: Few clouds. Alpine temperatures reaching 5.0 degrees. Freezing levels rising to 2500 m in the afternoon then dropping to 1400 m overnight. Ridgetop winds blowing light from the West.Sunday: Mostly sunny. Alpine temperatures -2.0. Freezing levels 2000 m and then falling to valley bottom overnight.
Avalanche Summary
On Wednesday, numerous solar induced cornice releases up to size 2 occurred and triggered slab avalanches on the slopes below. Some loose wet and dry avalanches initiated from steeper solar aspects.Expect this type of avalanche activity to persist through the forecast period.
Snowpack Summary
Surface faceting and surface hoar growth (up to 20 mm) has been prevalent on shady slopes and at upper elevations, while the surface snow on sun-exposed slopes and at lower elevations has been subject to daily melt-freeze cycles.Cornices are reported to be very large and weakly bonded. Wind and storm slabs are reported to be strengthening, but may continue to be sensitive to human-triggers. The weak layer of buried surface hoar sitting on a crust down around 70-120cm, and has been producing variable but sudden results in snowpack tests. This deep persistent weakness remains a concern because of the potential for very large avalanches particularly with heavy triggers such as cornice falls. Old deep persistent weaknesses, including basal depth hoar, are a concern in shallow snowpack areas.
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.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.