Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Regions
Kootenay Boundary.
Solar radiation is the primary factor driving the hazard this weekend. Expect conditions to change rapidly if the sun comes out.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
No significant snow in the forecast. Up to 5cm Friday night and another 5-10cm Sunday. Light to moderate ridgetop winds out of the southwest throughout weekend. Freezing levels spike Friday then cool off to around 1800m for the remainder of the period. For more detailed weather information see https://avalanche.ca/weather
Avalanche Summary
On Thursday two size 1 skier triggered slab avalanches were reported on northerly aspects that failed on a surface hoar layer down 20-25cm. The elevations of these avalanches were not reported.
Snowpack Summary
Cornices are large and looming. Old wind slabs are well bonded but could fail with daytime heating on solar aspects. The mid February layer is down 30-50cm and is a crust in most areas. This layer is generally well bonded to the overlying persistent slab. However, in isolated areas on northerly aspects at treeline elevations the February 10th surface hoar down 70-100cm is still producing moderate sudden planar shears in compression tests, though it has not been reactive to human triggers. This suggests a classic low probability, high consequence scenario.
Problems
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.
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.
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.