Regions
Northwest Inland.
Cranking winds accompanied by 5-10 cm will likely build new and reactive wind slabs at upper elevations. Deeper slabs may exist on leeward slopes.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
A change in the weather pattern is upon us as the jet shifts to a westerly flow allowing a series of Pacific frontal systems to track across the Interior Coastal Region.Tuesday: Mix of sun and cloud with a trace of new snow 5-8 cm. Alpine temperatures near -9 and ridgetop winds moderate with strong gusts from the SW. Wednesday: Cloudy with scattered flurries. Alpine temperatures near -10 and ridgetop winds moderate with strong gusts from the SW. Thursday: Mostly cloudy with a trace of new snow. Alpine temperatures high of -4 and ridgetop winds moderate-strong from the West. Freezing levels rising to 1000m.
Avalanche Summary
On Sunday, numerous natural wind slabs were reported up to size 1.5 which were triggered by the recent wind event. Previously, there was a report of a size 2.5 natural avalanche in the northern part of the region. This may have happened in the last 5 days and possibly failed on a persistent weak layer buried early february on a NW aspect in the alpine.
Snowpack Summary
Up to 20 cm of storm snow accumulating in the last week has been transported by the wind, and now sits on a variety of old surface conditions including isolated wind slabs, pockets of soft snow (5 to 10 cm deep), sun crusts, and surface hoar. A supportive rain crust exists below 1000 m. A layer of surface hoar that was buried on February 10th may exist 30 to 60 cm below the surface, but there's a fair bit of uncertainty regarding the reactivity and distribution of this layer. A stiff mid pack sits above weak sugary snow near the ground. Although possibly dormant, this basal weakness has the potential to produce very large destructive avalanches.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.