Avalanche danger is high due to loading from new snow or rain, and wind.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
The second pulse of warm and mild weather associated with the low pressure system off the coast is expected to spread moderate to heavy precipitation over the region tonight (10-15 mm) and through Friday (10-15 mm). Freezing levels could reach up to 2000m during the night and lower back down to 1800m tomorrow. A third wave of moisture with similar characteristics as the one before will be drifting inland on Friday night bringing another 15 mm of precipitation during the night and through Saturday. Freezing levels are expected to be around 2000m. Sunday is still looking warm but somewhat dryer. Winds are forecast to be moderate to strong from the southwest for the whole period.
Avalanche Summary
Several skier and explosive triggered avalanches up to size 2 out of treeline and alpine start zones were reported. Sluffing and shooting cracks were also observed as a slab was developing in the afternoon.
Snowpack Summary
Around 10 mm of heavy snow, or rain below 1500m, has accumulated over 5 cm which is sitting on a variety of surfaces; on a surface hoar and crust combo (referred to as the “late January surface hoar/crust” further down) in more sheltered areas, on a thin breakable crust in more wind affected areas or over windslabs on northeast aspects in the alpine. Significantly more load is expected to add on to the snowpack through the night and tomorrow (total 20-30 mm as rain up to around 2000m) driving the avalanche danger to rise and making travelling conditions very dangerous in the backcountry. The rain is expected to weaken the late January crust/surface hoar layer, therefore increasing the likelihood of avalanches stepping down to deeper weak layers. The mid-December crust/facet/surface hoar combo found down 50-95 cm and could come out of its dormant stage making for some very large avalanche potential .
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.
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.