Regions
Kootenay Boundary.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Monday
Weather Forecast
An "almost pineapple" weather pattern is setup across the province, and while the neighboring regions to the north receive the full brunt of the firehouse, the northern track of the jet leaves the South Kootenays with very little precipitation. SUN: FZLVL stays near 1500m, all day. Less than a mm of water is expected. 2km Winds; Mod SW decreasing throughout the day. MON: FRLVL lowers to 1200m. 10 - 15cm of snow is expected above 1200m, light rain below. Winds strong/extreme W, SW during daylight hours. Tue: A ridge of high pressure slides into the region bringing more seasonal cool temperatures, high solar & light winds.
Avalanche Summary
Two significant human triggered avalanches occurred on Thursday, before we had much wind or significant warming. 1. A group of sledders triggered a size 2.5 avalanche below treeline near 1700m in a moderately angled cutblock, resulting in a full burial. That same day, a snowboarder in the Nelson backcounty triggered a size 3.0 avalanche below treeline, SE aspect, 84cm in depth, 400m wide, running full path to the valley bottom. The snowboarder was able to cut out of the slide early and was unharmed. On Friday a group remote triggered a size 2.5 avalanche from 30m away on a SE facing slope near 2000m in the Slocan. The crown depth was 90cm, failing on the early Feb. SH. Sluffing was less of an issue Friday as storm snow settled out a bit.
Snowpack Summary
20-40cm of new snow is sitting on the Feb. 29 interface which consists of surface hoar on shady aspects and a thin sun crust on south aspects. A weak storm snow interface of well-preserved stellars is down approximately 50-60cm and reactive to human triggers on steep shady (cold) slopes at and below treeline. However the main snowpack feature of concern continues to be the surface hoar buried mid-February, which is now down 70-120cm and still giving sudden snowpack test results. This persistent weakness is susceptible to remote triggering and has the ability to propagate in low angled terrain, and the overlying slab structure creates the potential for step-down avalanches. Although generally getting deeper and harder to trigger, avalanche professionals throughout the region continue to treat this weakness with caution.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.