As this past week's storm snow continues to settle it will still be important to evaluate the bond between the old snow surface and the new snow. There is still potential for a weak sliding layer in isolated sheltered areas.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Friday
Weather Forecast
Friday: Scattered flurries / Light east wind / Alpine temperature -4Saturday: Flurries, accumulation 5-10cm / Light east wind / Alpine temperature -10Sunday: Mix of sun and cloud / Light west wind / Alpine temperature -13
Avalanche Summary
A few wind slab avalanches (mostly in the size 2 range), were observed failing with explosives on Tuesday and Wednesday in the alpine. There is a bit of uncertainty regarding how the new snow will bond to old surfaces which formed during last week's cold snap. Given this, there is still potential for skier and rider triggering in sheltered areas where buried surface hoar may exist or in wind exposed terrain where wind slabs maybe sitting on facets.
Snowpack Summary
Since Sunday up to 60cm of low-density snow has fallen with the highest amounts accumulating in the Lizard Range. Strong winds and slight warming have added cohesion to the new snow and reactive wind slabs exist in exposed terrain. The new snow buries a variable surface that developed over the last week of cold, dry, and windy conditions. This interface consists of scoured surfaces and wind slabs in wind exposed terrain, widespread faceting of the upper snowpack, and surface hoar up to 20mm in sheltered areas. In sheltered areas, you may find another layer of surface hoar in the mid to upper snowpack which was buried around December 10. The mid pack is generally well settled. The thick crust from mid-November is near the bottom of the snowpack and reports suggest that the crust is currently well bonded to the surrounding snow.
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.