Regions
Northwest Coastal.
Watch for wind transport through the day and stay clear of freshly wind loaded features.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
SUNDAY: snow starting in the afternoon with up to 10cm expected overnight, moderate westerly winds, freezing level of 1000m. MONDAY: cloudy with sunny breaks, moderate westerly winds, freezing level 1200m. TUESDAY: mainly sunny, light easterly southerly winds, freeing level 1200m.
Avalanche Summary
The only avalanche activity reported on Friday was skier triggered sluffing in steep terrain. Earlier in the week there were numerous explosive triggered storm slab avalanches up to size 2, although I suspect these slabs are becoming less reactive with time. At lower elevations (1500m and below), widespread loose wet avalanches were stepping down to size 2 wet slabs. In the far north, deeply buried persistent weak layers may still be reactive to large triggers such as a small avalanche stepping down or a cornice failure. On Thursday a skier triggered a size 2.5, deep persistent avalanche that released on basal facets on a SE aspect around 1700 m.
Snowpack Summary
40-90cm of settling storm snow sits above a melt freeze crust buried on February 12th which extends up to around 2000m elevation. The upper snowpack is reported to be bonding well to this crust. Moist snow may be found at lower elevations. Recent wind has redistributed the surface snow at higher elevations forming wind slabs in lee features. The early January surface hoar/facet layer is down around 1m+ and remains a concern for commercial operations. This layer seems the most reactive in the north of the region but may still be a concern in the south as well. Shallow snowpack areas in the east and north of the region may have a weak base layer of facetted snow on or just above the ground.
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.