Regions
Northwest Coastal.
Recent storm snow will likely take a few days to gain strength.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Another 5-10 cm of snow is expected for Thursday as freezing levels drop to 1200 m and alpine winds ease off to moderate but gusty southerlies. A brief drying ad clearing trend is expected overnight Thursday before another 5-10 cm falls on Friday with freezing levels down to 500 m and moderate southwesterly alpine winds. Unsettled weather is expected for Saturday with some sunny breaks in the afternoon and isolated light flurries. Freezing levels should remain at 500 m with light to moderate alpine winds.
Avalanche Summary
Reports from Tuesday include explosive-triggered 10-35cm thick storm and wind slab avalanche up to Size 2.0 at all elevations and on all aspects. Many natural wet loose avalanches up to Size 2.5 were also observed at lower elevations, some entraining the entire snowpack to the ground.
Snowpack Summary
Heavy rain has saturated the upper snowpack and resulted in wet, loose, and cohesionless surface snow as high as alpine elevations in the southern part of the region. As freezing levels drop, this should soon freeze into a solid surface crust with fresh wet snow stuck on top, depending on elevation. Meanwhile in the high alpine and as low as treeline elevations further north as much as 50 cm of recent snow and wind has formed new storm slabs and overloaded previous weaknesses buried within the snowpack, such as the mid-November crust-facet layer.
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.
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.