Regions
Northwest Coastal.
Although avalanche danger has decreased post-storm, take a cautious approach and gather your own snow pack information before committing to exposed terrain.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Light snowfall should taper off by late Saturday. Winds remain light to moderate from the south. The freezing level is falling towards valley bottom.
Avalanche Summary
A naturally triggered avalanche cycle was observed in response to the recent storm. At low elevations, many of these were wet and dug deep, failing to ground, up to size 2.5. At treeline and above, storm slabs and wind slabs were reported. In the north, large explosives triggered slabs up to size 3 failing on the November crust layer, with wide propagations at alpine elevations.
Snowpack Summary
Heavy rain which recently saturated the upper snowpack 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 may 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, up to 70 cm of recent snow and wind has formed new storm slabs. These have 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.