Regions
Northwest Coastal.
Variable winds and new snow are expected to form reactive slabs on a variety of aspects. Watch out for reverse loaded features.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Tuesday
Weather Forecast
TUESDAY: light snowfall is expected to bring up to 10cm through the day, mainly concentrated in the south of the region, moderate south easterly winds, 1200m freezing level. WEDNESDAY: mainly cloudy with isolated flurries, light to moderate southerly winds, 1200m freezing level. THURSDAY: light to moderate snowfall, moderate to light southerly winds, 1000m freezing level.
Avalanche Summary
Explosive control North of Stewart produced storm slab avalanches up to size 2 on Sunday.
Snowpack Summary
Between 15 and 25cm of new snow over the weekend combined with moderate winds has created wind slabs at treeline and in the alpine. A total of 50cm of new snow now sits on a crust below treeline and on sunny aspects, or surface hoar in isolated sheltered and shady locations. Below this an old crust buried around February 12th, that extends up to about 2000m can now be found down 60-80cm. A layer of surface hoar buried late in January remains a lingering concern in thin snowpack areas in the far North of the region. The snowpack at lower below treeline elevations may now be too shallow for avalanches in many places.
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.