Regions
Kootenay Boundary.
Avalanche danger is high due to loading from new snow or rain, and wind.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
The second pulse of warm and mild weather associated with the low pressure system off the coast is expected to spread heavy precipitation over the region tonight (20-30 mm) and through Friday (20-30 mm). Freezing levels could reach up to 2500m during the night and lower back down to 1800m tomorrow. A third wave of moisture with similar characteristics as the one before will be drifting inland on Friday night bringing another 20-25 mm of precip during the night and through Saturday. Freezing levels are expected to be around 1800m. Sunday is still looking warm but somewhat dryer. Winds are forecast to be moderate to strong from the southwest for the whole period.
Avalanche Summary
Multiple natural and skier triggered avalanches up to size 2.5 were reported within the storm snow some of which had impressive propagation potential.
Snowpack Summary
Around 20-25 mm of heavy snow, or rain below 1500m, has accumulated over 10-20 cm which is sitting on a widespread weak layer made of a hard crust topped by large surface hoar (referred to as the late January crust/surface hoar layer further down). Significantly more load is expected to add on to the snowpack through the night and tomorrow (total 40-60 mm as rain up to around 2200m) driving the avalanche danger to rise and making travelling conditions very dangerous in the backcountry. The rain is expected to weaken the late January crust/surface hoar layer, therefore increasing the likelihood of avalanches stepping down to deeper weak layers. The mid-January weak layer of buried surface hoar is now down 35-75 cm. The mid-December crust/facet/surface hoar combo found down 60 - 110 cm and could come out of its dormant stage making for some very large avalanche potential .
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.