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Confidence
Poor - Due to the number of field observations
Weather Forecast
Tuesday: A lingering above freezing layer of warm air may persist between 1700m and 3000m through the day Tuesday. Strong NW winds at ridgetop, light SW at treeline. No precipitation. Tuesday Night: 1cm to 10cm of snow, freezing level decreasing to valley bottom by nights end. Wednesday: Increasing cloud cover, winds decreasing to light NW throughout the day, no precipitation, freezing level at valley bottom. Thursday: Broken skies, light variable winds at all elevations, no significant precipitation, freezing level at valley bottom.
Avalanche Summary
No new avalanches have been reported recently.
Snowpack Summary
Up to 10 cm of new snow may now cover a thick, solid crust that extents up to 2100m and firm wind pressed surface higher than that. The recent winds have been light to moderate from the northeast and I suspect that you may find isolated fresh wind slabs forming in reverse loaded lee features on southern aspects. Below 2100m the crust is effectively capping the snowpack and protecting a couple of buried persistent week layers. Two layers of surface hoar can be found down between 50 and 80cm. Recent snow pack test indicate that these layers are unlikely to fail but could propagate widely if they do. I suspect that at upper elevations where these layers are not protected by the surface crust it may still be possible to trigger an avalanche from a thin or rocky spot. The mid-December crust is becoming harder to find but where it does exist (mainly at treeline elevations) it is over a meter down.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.