Regions
Northwest Coastal.
A prolonged, very active period of avalanche activity is ongoing. Be extremely cautious if venturing into the backcountry at this time.
Weather Forecast
A series of storm fronts will bring further wet and windy weather to this region. On Friday, a relatively weak system will bring 5-10 cm new snow and strong southwesterly winds. Freezing levels will stay at valley bottom. Over the weekend, a punchy storm will drop 20-30 mm precipitation on Saturday and 30-40 mm precipitation on Sunday. Freezing levels will go up to 1200 m on Saturday and 1600 m on Sunday. Winds will continue to be strong from the southwest.
Avalanche Summary
A natural avalanche cycle up to size 3 occurred on Wednesday affecting all aspects and all elevations. Along Bear Pass, 90% of the avalanche paths were reported to have run.
Snowpack Summary
A significant storm dropped 40 to 80 mm of precipitation on this region over the last 48 hours bring treeline snowpack depths into the 3-4 m range. The storm was accompanied by high winds and touchy fresh wind slabs and storm slabs now exist as a result. A rain crust exists below about 1000 m. With all the new snow, earlier weak layers are getting rapidly buried to the point where they are hard to trigger. A relatively thin layer of surface hoar or facets was reportedly buried New Year's day - this may have been the focus of some of the storm snow releases during the current storm; however, I suspect this layer will settle out quite rapidly. Lower down, it is still possible to find a surface hoar/crust/facet combo from mid-December. I suspect it would take a very heavy trigger such as a cornice fall to trigger this layer now, although if you are traveling in an unusually shallow snowpack area I'd still be cautious of it. The lower snowpack is generally well settled and strong.
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.
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.