Lookout for stiff wind slabs in the alpine. Likely trigger spots are steep and rocky alpine terrain with a shallow snowpack.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Friday: Cloudy with isolated flurries / Light easterly winds / Weak inversion with a alpine high of -15 C.Saturday: Cloudy with scattered flurries and 3-5 cm new snow / Light to moderate southerly winds / Alpine high -11 C.Sunday: 5-10 cm new snow overnight / Mostly cloudy / Moderate southwesterly winds / Alpine high of -12 C.
Avalanche Summary
Avalanche activity continues to taper since the last storm. On Wednesday, explosive avalanche control triggered only small size 1 slabs. On Tuesday, explosive control triggered numerous slab avalanches up to size 2.5 on northerly aspects above 1750m. These avalanches were reported to be failing on a previous graupel (small hail) interface and not digging deeper to the November crust layer.
Snowpack Summary
Recent storm slabs and wind slabs have formed on open leeward slopes and behind terrain features in exposed areas. The mid pack is reported to be well settled. There is sufficient snow on the ground for avalanches at treeline and alpine elevations, and possibly in some below treeline locations. Reports suggest typical treeline snow depths are around 110-150 cm, but a report from the east side of region indicated a much lower snow depth of around 90 cm. Limited reports suggest the crust from the middle of November is down 50-80 cm and the crust from early November is down 80-110 cm.
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.