Regions
Northwest Coastal.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The storm 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 precipitation. Tues. Night/Wednesday: Snow or rain 20-25mm, freezing level progressively falling from around 1500m to 700m, ridgetop wind 70-90 km/h SW-W easing during the dayThursday: A mix of sun and cloud, dry conditions, freezing level 500m overnight, 800m afternoon, ridgetop wind light SWFriday: Snow or rain beginning Thursday night 6-10mm, freezing level 700m overnight, 1000m afternoon, ridgetop wind 20-40 km/h SW
Avalanche Summary
Widespread natural activity was reported on the weekend during the first storm but tapered off a bit on Monday during the break between storms. Isolated natural and human-triggered slab avalanches up to size 3 were reported on Monday. More widespread natural activity is expected for late Tuesday and Wednesday during the current storm system.
Snowpack Summary
New storm snow is sitting on the slightly older storm slab that is roughly 50cm thick. These slabs sit on a weak layer which may consist of the following: hard wind slabs or wind-scoured slopes in exposed terrain, a thick layer of faceted snow on sheltered, shady slopes, isolated surface hoar on sheltered, shady slopes, and sun crust on steep solar aspects. Expect moist or wet snow at lower elevations, possibly with one or two new crusts near the surface. The mid February weak layer of surface hoar or a crust/facet combo is buried 1-1.5m deep. This layer continues to react in snowpack tests, primarily on sheltered north aspects at or below treeline. Basal facets and/or depth hoar remain a concern in shallow snowpack areas in the northern part of the region.
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.