Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The next Pacific frontal system will cross the South Coast on Tuesday resulting in strong wind and precipitation. Generally unsettled conditions are expected for Wednesday before another weak system affects the region Wednesday night or Thursday morning.Tuesday: Snowfall 20-30cm, afternoon freezing levels around 900m, ridgetop winds 40-60km/h SWWednesday: Cloudy with periods of sun, light intermittent snowfall 2-4cm, afternoon freezing levels around 700m, ridgetop winds 20-30km/h WThursday: Snowfall 5-15cm (might be Wednesday overnight), afternoon freezing levels around 700m, ridgetop winds 30-40km/h W-NW increasing in the afternoon
Avalanche Summary
On Sunday, numerous natural and human triggered slab avalanches up to size 3 were reported throughout the region. These were storm slab avalanches and occurred on all aspects and all elevation bands.
Snowpack Summary
Total storm snowfall amounts exceed over 1.5m during the past week and has settled into a storm slab with a typical thickness of 60-100cm. This storm slab is overlying a variety of old weak surfaces that developed during the past dry spell. They consist of weak facets, surface hoar, a scoured crust, wind press, or any combination of these. A poor bond exists to these old surfaces.Particularly of concern is the combination of buried facets on a crust being unusually reactive at treeline and below. Avalanche activity, whumpfing and snowpack testing at these elevations are showing easy sudden planar results on the facet/crust combo. Strong to extreme winds are shifting the new snow into deeper, and destructive wind slabs on lee slopes.The mid and lower snowpack are generally strong and well-settled. Basal facets and depth hoar are likely to exist in some parts of the region, but triggering has become unlikely.
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.