Avalanche Forecast
Regions: South Columbia.
Recently formed storm slabs are expected to remain reactive to human triggers on Sunday.
These slabs will be most reactive on wind-loaded slopes where the slabs are sitting on either a sun crust or a weak layer of surface hoar.
Confidence
Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather.
Weather Forecast
SATURDAY NIGHT: Cloudy with isolated flurries; 0-5 cm / Light southwest winds / Low of -6 / Freezing level 600 m.
SUNDAY: Mostly cloudy with isolated flurries; 0-3 cm, and another 5-10 cm overnight / Light west wind / High of 2 / Freezing level 1700 m.
MONDAY: Flurries; 5-10 cm / Moderate southwest wind / High of 1 / Freezing level 1600 m.
TUESDAY: Snow; 10-20 cm / Moderate southwest wind / High of 2 / Freezing level 1700 m.
Avalanche Summary
Numerous skier triggered storm slab avalanches up to size 1.5 were reported on Saturday. The storm slabs were most reactive were they were sitting on a sun crust or a weak layer of surface hoar.
Several very large human triggered persistent slab avalanches up to size 3 were reported last weekend. They occurred primarily in the Valhalla, Goat, and Kokanee Ranges typically on north through southeast facing slopes at treeline elevations. They were failing on a layer of surface hoar down 70-120 cm.
Snowpack Summary
15-20 cm of new snow and moderate southwest winds on Friday night formed fresh storm slabs that will be most reactive in wind affected terrain.
The 15-25 cm of recent snow is sitting on a variety of surfaces including hard wind affected snow, sun crusts on southerly slopes, and surface hoar on shady or sheltered slopes. Expect storm slabs to be most reactive where they are sitting on either a sun crust or surface hoar.
The late February persistent weak layer combination of crust, facets and surface hoar is down 40-50 cm. Reports suggest this layer is becoming less reactive in most areas.
Two additional persistent weak layers from late January and mid-February are down 80-120 cm. They both consist of surface hoar and/or melt-freeze crusts. Recent trends indicate these layers have only been reactive in southern Selkirks around the Valhalla, Kokanee, and Goat Ranges. Several natural and human triggered avalanches occurred on these layers last weekend.
Terrain and Travel
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be especially cautious as you transition into wind affected terrain.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Avalanche Problems
Storm Slabs
15-20 cm of new snow and moderate southwest winds on Friday night formed fresh storm slabs that will be most reactive in wind affected terrain, especially where the recent snow is sitting on a weak layer of surface hoar.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1.5 - 2.5
Persistent Slabs
Persistent weak layers of surface hoar and/or crust can be found 40 to 120 cm deep.
The problem is most likely found in the southern part of the Selkirks (e.g. Valhalla, Goat and Kokanee ranges), especially on open convex slopes at treeline elevations.
This problem exists on all aspects, however increased reactivity has been noted on northeast through southeast facing slopes.
Aspects: All aspects.
Elevations: Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3