Regions
Northwest Coastal.
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Confidence
Fair - Due to the number of field observations
Weather Forecast
Mainly clear cool weather is expected until late Monday, when a system is expected to brush up against the coast and bring light snowfall. Freezing levels are near valley bottom. Moderate SE winds.
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. Explosives testing produced smaller results by Friday.
Snowpack Summary
Recent heavy rain affected southern parts of the region up to alpine elevations, while the far north remained drier and sports a weaker snowpack in general. Areas which previously received rain have probably now formed a hard frozen crust. High alpine and far northern areas are likely to have wind slabs and large fragile cornices. Deeper in the snowpack, weaknesses such as the mid-November crust-facet layer are still of concern to some operators.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.