Continued strong ridgetop winds are driving the Danger Ratings in the alpine.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Saturday
Weather Forecast
Light snow is forecast overnight as the weakening cold front moves east from the coast. By Saturday another pacific frontal system will spread light amounts of precipitation accompanied by strong southwesterly ridgetop winds and gradual warming temperatures.Friday: Cloudy with sunny breaks and flurries. Alpine temperatures near -8. Ridgetop winds light from the SW. Saturday: Cloudy with snow amounts 5-10 cm. Alpine temperatures -6. Ridgetop winds strong from the SW.Sunday: Cloudy with snow amounts near 10 cm. Alpine temperatures -4. Ridgetop winds moderate from the SW.
Avalanche Summary
Explosives control saw a couple size 1.5 slab avalanches from NE-E aspects around 2000 m. I suspect that wind slabs may be easily rider triggered with the recent strong to extreme winds. Use extra caution on cross-loaded slopes, and in the immediate lee of ridgelines. Small loose dry avalanches are likely from steeper slopes, and do not support a significant problem unless you were pushed into a terrain trap like a cliff, or a gully.
Snowpack Summary
Incremental snowfall amounts have buried surface hoar crystals and a faceted upper snowpack. Snowpack depths at treeline seem to vary from 50 - 110 cm and widespread wind effect is noticeable in the alpine and at treeline.Down 30-40 cm sits a surface hoar/ facet/ crust interface. This layer seems to be less reactive to snowpack testing. However, with windy, warmer temperatures and new snow it may become more reactive as the slab above it develops.Near the base of the snowpack, weak sugary facets and depth hoar exist. This layer may be stubborn to trigger, especially in deeper snowpack areas. In shallower locations the likelihood may increase especially on a steep, convex slope. In some areas it is below threshold below treeline, and early season hazards like open creeks, and stumps exist.
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.