Regions
Northwest Coastal.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Synopsis: There is a brief break between weather systems on Saturday before the next frontal system arrives late Saturday and into Sunday. Saturday: Cloudy with light snow and possible sunny breaks. The freezing level is around 400 m and winds ease to moderate from the southwest. Sunday: Moderate snowfall – 10-20 cm. The freezing level is around 500 m and winds are moderate to strong from the southwest.Monday: Cloudy but drier. The freezing level remains around 500 m and winds are light from the southwest.
Avalanche Summary
A natural avalanche cycle was likely on Friday in response to heavy snow and strong winds. Observations from Thursday were limited due to poor weather, but there were a few reports of easily triggered slab avalanches up to size 1.5 failing within the storm snow. Most of these slides were from below treeline elevations.
Snowpack Summary
30-60 cm of new snow had fallen by Friday morning, accompanied by strong southwest winds. Deep and dense wind slabs have formed in exposed lee terrain. This new snow fell on a crust, old wind slab, and/or surface hoar depending on aspect and elevation, and may not bond well initially. Cornices that now loom over many features may become weak with continued growth and/or daytime warming. The mid and lower snowpack layers are generally well settled and strong.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.