Regions
Kootenay Boundary.
Use increased caution on sun-exposed slopes during the afternoon heat.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Wednesday
Weather Forecast
The ridge of high pressure will be the prominent feature for Monday and Tuesday before a weak storm system arrives on Wednesday. On Monday, mainly sunny conditions are expected with freezing levels as high as 2500m. Alpine winds are expected to be moderate-to-strong from the W-NW. On Tuesday, a mix of sun and cloud is expected with freezing levels reaching around 2500m. Alpine winds are forecast to be moderate from the SW. On Wednesday, precipitation is expected and models are currently showing 5-10mm but freezing levels are forecast to be around 2000m.
Avalanche Summary
On Tuesday and Wednesday there were reports of small wind slabs being triggered by skiers and explosives. On Friday, natural sun-triggered sluffing was reported from steep sun-exposed slopes. As warm conditions persist on Monday, it may still be possible to trigger old pockets of wind slabs. During the afternoon it may be possible to trigger sluffing from steep sun-exposed slopes.
Snowpack Summary
Variable snow surface consists of wind-affected snow or wind-scoured crusts in exposed alpine areas, moist snow or sun crust on sun-exposed slopes, or 5-10cm of dry snow overlying an old crust in shady and sheltered areas. At higher elevations, ongoing winds may be continuing to build thin wind slabs in leeward features. Lower elevations are undergoing daily springtime melt-freeze cycles. The most prominent feature in the snowpack is the thick late-February crust, down 5-20 cm. This crust is supportive all the way to ridge crest and is effectively "capping" the snowpack, keeping riders from stressing any deeper weak layers. There are still weak layers below this crust that we'll continue to monitor, but for now these layers are dormant. We would likely need significant warming and/or heavy loading to re-activate them.
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.