Highly sensitive storm slabs are everywhere. Conservative terrain selection is essential for safe travel.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Tuesday: Mainly cloudy with another 5-10cm of snow, moderate southerly winds and freezing levels around 1100m. Wednesday: A mix of sun and cloud but generally dry, light winds and freezing around 1000m. Thursday: As much as 20-30cm expected. Strong southerly winds and freezing levels around 1500m.
Avalanche Summary
Reports from Sunday include numerous Size 1-2 storm slab avalanches direct and remotely triggered by skiers on slopes as low-angled as 20 degrees, as well as widespread whumpfing in flatter terrain as low as 1300m.
Snowpack Summary
Approximately 50cm of accumulating storm snow is bonding poorly to a widespread layer of surface hoar, facets, and/or sun crust. 10-20 cm below this is a second buried weak layer of surface hoar and/or a crust. Recent snowpack tests produced clean and sudden fractures on both these weaknesses with only moderate force. The mid and lower snowpack is generally strong, with the exception of shallower snowpack areas that may be more faceted. At lower treeline elevations recent rains have saturated the upper snowpack. At higher elevations moderate to strong southwest winds have recently loaded lee features at treeline and in the alpine.
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.