Regions
Kootenay Boundary.
Recently formed wind slabs on high elevation north aspects may remain reactive to triggering. Extra caution is needed around any slopes exposed to large cornices during the heat of the day.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
WEDNESDAY: Cloudy with isolated flurries / Moderate south wind / Alpine temperature 2 / Freezing level 2000mTHURSDAY: Flurries / moderate to strong south wind / Alpine temperature 3 / Freezing level 2100 mFRIDAY: Flurries / Light to moderate southeast wind / Alpine temperature 3 / Freezing level 2300m
Avalanche Summary
On Sunday, natural sluffing was reported from very steep terrain. Ski cutting was triggering size 1 sluffs with the recent storm snow sliding on a crust. On Saturday, isolated natural storm slab avalanches were reported with thickness of 20 cm. On Wednesday, the main concern is lingering wind slabs in high elevation north facing terrain.
Snowpack Summary
The region is expected to have entered a period of widespread melt-freeze conditions on all aspects and elevations except for high north facing terrain where the surface snow is expected to remain dry. In high elevation terrain, recent strong southwest winds and new snowfall has formed wind slabs in leeward features. At lower elevations and on sun exposed slopes, there are likely several well bonded crust layers in the upper snowpack. A rain crust which was buried on March 21 extends into the alpine is now down 60-80 cm. This crust was the bed surface for several avalanches during the solar cycle at the end of last week. At elevations above around 2100m, the February persistent weak layers may still be lingering down around 100-150cm and weak basal facets may still be lingering in shallow snowpack areas. These deep weak layers appear to have gone dormant but an isolated avalanche or cornice fall still has the potential to step down in the right conditions.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.