Regions
Northwest Inland.
Confidence
Fair - Due to the number of field observations
Weather Forecast
The precipitation is expected to ease late Wednesday and a ridge will build on Thursday. Another frontal system is expected for Friday but should only result in light flurries. Tues. Night/Wednesday: Snow or rain 3-6mm, freezing level progressively falling from around 1500m to 900m, ridgetop wind 60-80 km/h SW-W easing during the dayThursday: A mix of sun and cloud, dry conditions, freezing level 500m overnight, 1000m afternoon, ridgetop wind light SWFriday: Snow or rain beginning Thursday night 6-10mm, freezing level 700m overnight, 1200-1500m afternoon, ridgetop wind 20-40 km/h SW
Avalanche Summary
Avalanche activity has tapered off since the weekend but isolated activity is still being reported. Reports from Monday of natural and human-triggered storm slab avalanches up to size 1.5. In thinner snowpack areas, isolated activity up to size 2 has been reported on the early-Feb layer down 60-80cm.
Snowpack Summary
Roughly 20-50 cm of dense storm snow now sits on a weak layer consisting of surface hoar and/or a thick layer of faceted snow on shady slopes at all elevations, a sun crust on steep solar aspects, and various wind affected surfaces in exposed terrain. Strong southwest winds have created dense wind slabs on exposed lee slopes and in cross-loaded features. The early February weak layer of facets, crusts, and/or surface hoar is buried down about 60-100 cm. Test results and isolated avalanche activity suggest this layer is still reactive to human-triggering. Basal facets and depth hoar remain a concern in areas with thin or variable snow cover.
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.