Regions
Northwest Coastal.
Avoid steep, fat looking slopes and wind loaded features. They could be reactive to human triggering through the storm on Tuesday
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Tuesday
Weather Forecast
TUESDAY: Light snowfall brings up to 15cm overnight and 10 through the day, light to moderate southwesterly winds, 1000m freezing level. WEDNESDAY: Flurries with accumulations of up to 10cm. light westerly winds, 1000m freezing level. THRUSDAY: mainly sunny, light and variable winds, 1000m freezing level.
Avalanche Summary
Wind slab avalanches were triggered by explosive control on Sunday and lingering stubborn wind slabs may still be reactive to human triggering. Several natural and artificially triggered cornice collapses in the last week have caused large avalanches in the alpine. On Thursday of last week, a natural size 3.5 persistent slab avalanche was reported in Bear Pass. This avalanche occurred on a northwest aspect at 1350m elevation and released on the late-February surface hoar layer.
Snowpack Summary
New snow is falling on widely wind effected old surfaces, burying wind pressed snow in exposed terrain and soft or hard slabs in lee features. Moist snow can be found at lower elevations and on solar aspects. A layer of surface hoar or facets down 70-100cm can be found in areas north of Stewart sitting below Marchs accumulated storm snow. Recent avalanche activity suggest that we may be approaching a critical load on this interface. An older crust/facet layer buried in early February can now be found around 80-120 cm below the surface, however, this layer has been dormant recently. Cornices are reported to be large and fragile.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.