Regions
Northwest Coastal.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Saturday night: 10-15cm further snow, with the freezing level near 1300m. Strong winds. Sunday: Flurries or light snow. Strong winds easing. Freezing level gradually lowering.Monday: A moist north-west flow should bring local snow to areas very close to the coast and flurries elsewhere. Gusty westerly winds. Tuesday: Light snow, turning to moderate snow by afternoon as the next system pushes onshore.
Avalanche Summary
Several natural and explosives-triggered avalanches have been reported, with observations coming in every day this week. Many have been in the size 2-3 range, mostly failing on an instability in the storm snow and occasionally failing on facets below the storm snow.
Snowpack Summary
As one operator describes it, "oodles" of storm snow has fallen over the past week (anywhere from 1-3m). Strong winds, which have switched direction several times, have created deep wind slabs on lee- and cross-loaded slopes. Warming, heavy snow and strong winds this weekend will increase avalanche danger once again. At low elevations, rain falling on the snow could weaken surface layers and lead to large moist avalanches. Of concern deeper in the snowpack is a buried facet layer below the storm snow and a crust /facet combo which exists below treeline and recently gave easy, sudden collapse results in compression tests.
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.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.