Regions
Northwest Coastal.
This is a good time to avoid avalanche terrain.
Weather Forecast
Monday night: Clear. Light to moderate south winds with freezing levels remaining near 3000 metres.Tuesday: Sunny. Light to moderate south winds. Alpine high temperatures around +8 with freezing levels remaining near 3000 metres and staying elevated overnight.Wednesday: A mix of sun and cloud. Light east or southeast winds. Alpine high temperatures around +5 with freezing levels around 2700 metres and decreasing a bit overnight.Thursday: A mix of sun and cloud with cloud increasing over the day. Light to moderate south winds. Alpine temperatures declining from +4 to +1 over the day as freezing levels drop from 2500 to 2000 metres, steadying overnight.
Avalanche Summary
Reports from the Shames area on Sunday showed evidence of what was likely a widespread natural avalanche cycle that produced at least several very large (size 3) slab avalanches running the full extent of their respective avalanche paths. More numerous audible large avalanches were also reported. The failure plane in these slides appeared to have been our most recent storm snow interface. Even more numerous, smaller loose wet avalanches were observed. All of this activity was focused on steep, sun-exposed aspects. This type of activity can be expected to continue, potentially expand to all aspects, and intensify as temperatures remain elevated and overnight cooling remains weak.
Snowpack Summary
Between 50 and 100 cm of settled snow forms the upper snowpack, the product of storms since the drought ended on March 10. At lower elevations this precipitation came as rain. With the help of warming temperatures, the recent snow has settled into a slab that covers a variety of old snow surfaces. These include crusts on solar aspects, facets on shaded aspects at higher elevations, and surface hoar in shaded and sheltered locations. Not much further below this storm snow interface is a second weak layer buried on February 19, primarily made up of weak facets and surface hoar crystals. Recent avalanche activity was more or less equally split between these two layers. The lower snowpack is generally strong.The Avalanche Activity section below shows heightened recent avalanche activity. Our recent storm snow has settled into an unstable slab over a range of lingering old weak layers formed during the cold spell. For the near term, expect warm temperatures to keep the snow stability balance near or beyond its tipping point.
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.