Significant variation in storm snow totals have occurred within the region with the south receiving the most. The danger rating will be HIGH on Tuesday in the alpine for the south.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
Overnight and Tuesday: The low pressure system stalls over south-eastern British Columbia tonight bringing light to locally moderate precipitation in the southern Kootenays before the arctic front moves further south tomorrow. Mainly dry conditions for Tuesday with a chance of light snow over the southern portion of the region. The winds building light to moderate from the north-east and freezing levels to valley bottom.Wednesday: Outbreak conditions continue; cold and dry. The winds will be light to moderate northerly.Thursday: The arctic air persists over the interior, cold and dry.
Avalanche Summary
Numerous size 1.5 avalanches have been reported as a result of explosive work. With the forecast precipitation and winds to continue in the southern portion of the region tonight, I suspect the chance for avalanche activity to be heightened through Tuesday.
Snowpack Summary
The snow distribution varies greatly across the region but average depth of snow at treeline is approximately 60-80cm.The storm over the weekend deposited 10-20cm of storm snow in the northern portion of the region while the southern reaches of the forecast region received 30-50cm. These storm slabs are sitting on-top of weak surface layers of facetted crystals and melt/freeze crusts. In areas that received more snow, there is likely a cohesive storm slab developing that may overload these weak layers or may make them primed for human triggering. To complicate the scenario, north winds in the forecast will likely deposit wind slabs on south facing slopes.The deeply buried early season crust near the base of the snowpack continues to be a concern. There have been reports of weak sugary crystals at the crust interface that may create an easy sliding surface and allow for wide propagations. The weight of new snow may be enough to 'wake up' these deeper layers. If so, they have the potential to produce large, destructive avalanches.
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.