Fresh storm slabs that formed over the weekend may be reactive to rider triggers especially on slopes that have seen more wind loading.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Monday
Weather Forecast
Unsettled conditions continue overnight into Monday as an upper trough moves from the north bringing flurries tonight. A cool arctic air mass will dominate the region by Tuesday bringing colder, dryer conditions. Monday: Mostly cloudy with flurries. Alpine temperatures near -13 with light winds from the northeast. Tuesday/ Wednesday: Mix of sun and cloud. Alpine temperatures dropping to -20 with light winds from the northeast.
Avalanche Summary
On Saturday, numerous natural storm slab avalanches were reported. These avalanches were up to size 2 and running on north-northeast aspects above 1700 m. Explosive control also triggered several slabs up to size 2. The crowns were 20-40 cm deep and running up to 160 m in length. These slabs were mostly failing on an old storm interface and reports haven't indicated any avalanche actively on the buried November crusts. On Sunday, numerous explosive triggered slab avalanches were reported. These were up to size 2 from all aspects. Rider triggers are likely on Monday.
Snowpack Summary
New storm slabs and wind slabs have formed on open leeward slopes and behind terrain features. The threshold for avalanches has been exceeded at treeline and in the alpine as reports suggest that the snow depth at treeline is typically 110-150 cm but a report from the east side of region shows only 80 cm at treeline. The snowpack is still developing below treeline and has yet to reach threshold. Limited reports suggest the crust from the middle of November is down 50-80 cm and the crust from early November is down 80-110 cm.
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.