Regions
Northwest Coastal.
Touchy conditions are expected. If you have questions about the snowpack, conservative terrain selection is always the answer.
Confidence
Moderate - Wind effect is extremely variable
Weather Forecast
A dry ridge of high pressure is expected to develop for the forecast period. Expect increasingly clear skies and light ridge top winds. Alpine temperatures are expected to remain between -14 and -20.
Avalanche Summary
Due to inclement weather, observations were generally limited on Saturday, but a widespread storm slab cycle to size 2 was observed in the north of the region. Natural avalanche activity will likely taper-off with forecast clearing. However, human-triggered avalanches will remain a concern for the forecast period, especially at elevations or in parts of the region where recent storm accumulations have settled into a cohesive slab.
Snowpack Summary
Between 25cm and 40cm of new snow fell on Friday night and Saturday. Winds associated with the storm were highly variable. In areas (or at elevations) where the wind was strong, there may be a cohesive and reactive storm slab. In areas where the winds were light, you're more likely to find loose powder. The new snow overlies a touchy layer of sugary faceted snow and well-developed surface hoar which is reported to exist on all aspects and elevations. Due to the persistent nature of these underlying crystals, newly formed storm slabs may remain reactive for the foreseeable future. Adding to the mix of weaknesses in the upper snowpack are a few other surface hoar layers that developed throughout December and late November which you may now find buried in the top 100cm. The weight of the new snow (or a surface avalanche in motion) may cause these layers to "wake up" resulting in larger, more destructive avalanches.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.