Warm, windy and wet weather is expected to result in natural avalanche activity and increased avalanche danger.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Continued heavy rain, or wet snow at alpine elevations, is expected for Wednesday with strong to extreme Southerly alpine winds and freezing levels hovering around 2000 m. Thursday could see around 20 cm of fresh snow with light to moderate southeastery alpine winds and freezing levels as low as 1500 m. Friday is looking mostly dry with a mix of sun and cloud, light winds and freezing levels down around 1000 m.
Avalanche Summary
Reports from Monday include small skier-controlled wind slabs on leeward alpine slopes. Natural avalanche activity is likely with heavy loading from snow, wind, and rain.
Snowpack Summary
Heavy rain, wet snow and wind has formed new storm slabs and is overloading previous weaknesses buried within the snowpack, such as crusts and associated facets. While at treeline and below, the upper snowpack is becoming saturated, loose, and cohesionless. The snow pack depth drops significantly below treeline with essentially no snow below 1600 m.
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.
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.