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 - Wind effect is extremely variable
Weather Forecast
Wednesday: Cloudy with some sunny periods and moderate-strong (60 km/h) SW winds. Alpine temperatures high of -10.Thursday: Snow 5-10 cm with strong SW winds. Alpine high of -6 and freezing levels 900 m. Friday: Mix of sun and cloud and a trace of new snow. Moderate- strong ridgetop winds from the SW.
Avalanche Summary
On Monday, no new avalanche activity was reported. On Sunday, numerous natural wind slabs were reported up to size 1.5 which were triggered by the recent wind event. With forecast snow and strong winds reactive wind slabs are likely over the next several days.
Snowpack Summary
New snow 5- 15 cm is slowly burying a plethora of old snow surfaces including isolated wind slabs and wind press, sun crusts, and surface hoar. The new snow may have a poor bond to these interfaces. 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 especially in shallower snowpack areas. Below 1000 m a strong supportive rain crust exists.
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.