Regions
Northwest Inland.
Strong winds have been forming new wind slabs up high while the bond beneath our new snow remains weak. Err on the side of caution while danger is still elevated.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Wednesday: Mainly cloudy. Strong to extreme west winds. Freezing level to 1000 metres with alpine high temperatures around -8.Thursday: Increasingly cloudy with flurries bringing 3-5 cm of new snow by end of day, increasing overnight. Light southeast winds. Freezing level near valley bottom with alpine high temperatures around -9.Friday: Cloudy with continuing flurries and another 3-5 cm of new snow. Light variable winds. Freezing level to around 800 metres with alpine high temperatures around -8.
Avalanche Summary
Reports from Sunday again included numerous observations of ski cutting producing size 1.5 storm slab releases on small rolls. These slabs were failing at an upper storm interface before stepping down to the full depth of our recent storm snow (about 40 cm). Conservative terrain selection is likely to have limited the size of these results.On Saturday, ski cutting on convex rolls below treeline produced size 1.5 slabs in the recent storm snow down 30 cm deep. These failed over the widespread melt-freeze crust and gathered substantial mass as they traveled downslope.
Snowpack Summary
Up to 40 cm of storm snow now overlies a range of old snow surfaces, including two layers of surface hoar existing on shaded aspects at high elevations as well as a melt-freeze crust on all aspects at treeline and below. This storm snow has been showing a poor bond to the shallowest of these buried weak layers, down about 40cm. Recent strong winds have redistributed the new snow into thicker and likely more reactive wind slabs on a range of aspects wind-exposed terrain. Southwest winds have been the most recent.Deeper in the mid-pack, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist from mid- and late-February and a surface hoar/ crust layer from January is buried around 150 to 200 cm. Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north.
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.