This weekend's weather forecast includes higher freezing levels and rain to mid-mountain elevations. This will have a destabilizing effect on the snowpack with avalanches increasing in size and frequency.
Confidence
Fair - Freezing levels are uncertain on Friday
Weather Forecast
Friday: Light snowfall / Moderate to strong southwest winds / Freezing level at surface climbing to about 1800m in the eveningSaturday: Up to about 30cm of snow at higher elevations / Moderate to strong southwest winds / Freezing level at about 1800mSunday: Up to about 30cm of snow / at higher elevations / Moderate to strong southwest winds / Freezing level up to about 1800m
Avalanche Summary
In recent days natural wind slab avalanches to size 1.5 were reported in response to new snow and wind.
Snowpack Summary
In general, about 20-40cm of storm snow overlies small surface hoar crystals in sheltered areas, a sun crust on solar aspects and wind slabs in exposed terrain. The recent snowfall exists as pockets of wind slab in exposed terrain. Further snowfall, wind and warming will add to the reactivity and destructive potential of this developing storm slab. There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies up to a metre below the surface, and includes weak surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although natural avalanche activity has tapered-off at this interface, destructive avalanches are still a concern with recent reports of rider-triggering in alpine terrain. For the most part, the mid and lower snowpack are strong and well consolidated. Weak basal facets exist in some areas, but triggering has now become unlikely.
Problems
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.
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.