Regions
Kootenay Boundary.
Storm slabs are settling and gaining strength but the deeply buried persistent weak layer continues to be a concern for human triggering.
Confidence
Moderate - The weather pattern is stable on Tuesday
Weather Forecast
Tuesday: mainly cloudy with sunny breaks, no snow expected, light westerly winds, -5C at 1550m. Wednesday: overcast with snow starting in the afternoon and up to 5cm expected overnight, light southerly winds, -5C at 1500m. Thursday: clearing, isolated flurries possible early in the day, light southwesterly winds, freezing level rising to 1500m.
Avalanche Summary
Although avalanche activity seems to be slowing we continue to receive reports of natural and skier triggered wind and storm slab avalanches up to about size 2 releasing down 20 to 30cm. No new reports of any avalanches releasing down to the deeper persistent weak layers.
Snowpack Summary
A soft storm slab 20-30 cm deep can be found across most of the region. This may be sitting on a layer of surface hoar that was buried on January 27th. Some areas have reported that previous strong winds destroyed this surface hoar, and may have stripped the old surface back to a hard rain crust before the recent storm snow arrived. At lower elevations the storm slab may also be found on top of one or two thin freezing rain crusts up to about 2100 meters. Deeper in the snowpack, the persistent weak layer that was buried January 4th is now down 80-120 cm and continues to give sudden planar fractures in snowpack tests in some areas.
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.