Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Monday: No snow. Sunny breaks. Light winds. Freezing level around 1200 m.Tuesday: Light snow. Light S winds. Freezing level around 1100 m.Wednesday: Light snow. Light winds. Freezing level around 900 m.
Avalanche Summary
A widespread natural avalanche cycle to size 3.5 occurred on Friday and Saturday. Numerous large slabs failed on a surface hoar/crust weakness. Loose wet avalanches were prevalent below treeline, and a size 2.5 wet slab was reported, gouging to ground in the lower track on Saturday.
Snowpack Summary
The recent storm delivered 60-70 mm of precipitation, which fell with warming temperatures, dropping rain below about 1800 m. A subsequent drop in temperature has left a supportive frozen crust up to treeline. Strong south to south-westerly winds during the storm created touchy wind slabs on lee terrain. A weak layer of buried surface hoar and/or a crust was overloaded during the storm, creating a widespread avalanche cycle. The lower snowpack is well settled.
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.
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.