Recent warm temperatures have helped settle the wind slab problem but there is still potential for triggering deep slides in wind loaded terrain.
Confidence
Fair - Wind effect is extremely variable
Weather Forecast
Synopsis: The ridge of high pressure finally flattens allowing a weak disturbance to slide down from the northwest bringing more cloud, moderate westerly winds, and a chance of flurries on Friday. Another pulse is expected on Saturday afternoon maybe 3-5 cm. The snow level stays near valley bottom on Friday and Saturday. Sunday is still a little fuzzy but it looks like we will see moderate precipitation. The freezing level should start to climb to 800 m by the end of the day and winds are generally light.
Avalanche Summary
Recent activity has been primarily loose wet sluffs in steep sun-exposed terrain. On Wednesday there was one report of a size 1.5 wind slab avalanche on an east aspect in the alpine. This slide was triggered by a cornice fall. Earlier in the week there were numerous reports of natural and rider triggered wind slabs up to size 2.5 from southerly aspects as a result of outflow winds.
Snowpack Summary
In open alpine terrain you will find heavily wind affected surfaces with hard and soft wind slabs on south and west aspects and scoured surfaces or dense wind-pressed snow on windward slopes. Steep south facing slopes may also be going through a melt-freeze cycle. In sheltered areas at and below treeline you might find dry faceting powder with surface hoar (SH) growing above. A layer of SH buried last weekend is now down 10-20 cm and was reported to be widespread - one to watch when the snow returns. The mid-December SH layer may still be lurking in specific areas (sheltered, shady, near open water sources) down 40-70 cm. Below 2000 m and buried 60-100 cm deep you might find a crust with facets or mixed forms above or below. One recent snowpack test gave a hard pops result on this layer, meaning its probably difficult to trigger but if triggered it could produce large deep slabs.
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.