Recent avalanches have failed on a deeply buried weak layer. Although the chances of triggering a deep slab are dropping, the consequences remain high.
Confidence
Fair - Due to the number of field observations
Weather Forecast
A mix of sun and clouds on Monday with forecast alpine temperatures near -2.0 and light SE ridgetop winds. As the ridge starts to break down Tuesday, we'll see a series of weak storm systems mainly confined to the coast and traveling northward. These systems will bring light snow accumulations as the freezing levels hover around 1000 m. Outflow winds, bringing cooler dry air will persist.
Avalanche Summary
No new observations reported for Sunday. A natural cycle up to size 3 was observed throughout last weeks storm. These included wind slabs and storm slabs, primarily at alpine elevations; and loose wet and wet slab avalanches at treeline and below. Notably, some of these events failed on a crust /facet layer buried in late November and were more than 1 metre deep Thursday and Friday. On Saturday, a vehicle remotely triggered yet another slab 1m deep, on a north-facing slope in the alpine.
Snowpack Summary
The recent prolonged storm dropped 100-200 mm of water, with fluctuating freezing levels bringing rain at times to alpine elevations. Snow also accumulated above treeline, leading to deep wind slabs. Storm and winds slabs may remain problematic for a day or two. However, my bigger concern is a buried crust/facet layer which formed in November and is now down 1-2 m. This woke up with the recent storm snow loading and has the potential for deep slabs and wide propagations, and does not inspire huge confidence. The likelihood of triggering this beast is dropping, however the consequences remain high.
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.