Regions
Northwest Coastal.
This Will be a Week of Dubyas: Windy, Wet and Warm! Expect increasing hazard and widespread natural avalanche activity by Tuesday.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Monday: Moderate rain or snow 15-25 mm. The freezing level could rise to 1800 m. Ridge winds could be pushing 100 km/h from the S-SE. Tuesday: Heavy rain or snow. The freezing level peaks near 2000 m and winds are still cranking from the S-SE. Wednesday: Cloudy with showers or flurries. The freezing level should start to drop, maybe as low 1500 m, but the strong southerly winds continue.
Avalanche Summary
A couple fresh natural windslab avalanches were reported from an area northeast of Stewart on Friday. These slides were observed on west facing slopes near treeline, and were an average of 20 cm deep. Similar activity is possible throughout the region.
Snowpack Summary
Conditions vary significantly throughout the region. The common theme is that the snowpack is generally shallow, quite facetted (sugary), and very wind affected. 5-15 cm of new snow now covers a mix of surface hoar or faceted snow in sheltered areas, and wind slab or ice crusts in exposed terrain. Strong NE-SE winds have created dense new wind slabs in open north or west-facing terrain. Old hard wind slabs may also be lurking underneath. The mid-November crust-facet layer is now 40-60 cm deep and continues to show easy to moderate shears in snowpack tests. Deeper in the snowpack, at 80 cm down there is another crust that is breaking down and becoming bonded to the surrounding snow.
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.
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.