Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Lizard-Flathead.
Snowfall amounts will vary across the region, with 30 cm possible in localized areas by Monday morning. Treat the hazard higher if more than 30 cm of new snow is found. Be cautious of overhead exposure, as cornice falls could trigger slab avalanches.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
MONDAY: Cloudy with early-morning snowfall, accumulation 10 to 20 cm and possible localized amounts around 30 cm from convective flurries, light northeasterly winds, alpine temperature -12 C, freezing level below valley bottom.TUESDAY: Partly cloudy with light snowfall, accumulation 1 to 3 cm, light westerly winds, alpine temperature -8 C, freezing level 1000 m.WEDNESDAY: Mostly cloudy, light southwesterly winds, alpine temperature -5 C, freezing level 1300 m.
Avalanche Summary
On Saturday, a large slab avalanche was triggered in the west of the region. See this MIN post for a photo and more details. A report of a small wind slab avalanche at treeline was also provided to us.
Snowpack Summary
Substantial amounts of new snowfall are expected in the region, with accumulations that could reach 30 cm in localized areas. The new snow will fall on a melt-freeze crust on sunny aspects and all aspects below 1700 m. A surface hoar and crust layer buried mid-March is found around treeline at a depth of about 70 cm, with weak surface hoar on northerly aspects and the crust elsewhere. Deeper in the snowpack, the late-November weak layer is composed of sugary facets around a crust, which is buried around 200 to 300 cm and is currently dormant.At ridgetop, cornices are large and were actively failing over the last week.
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.