Watch for variable wind loading patterns as you gain elevation and maintain avoidance of overhead hazards like cornices and large avalanche paths. A heavy trigger in the right location still risks triggering a very large and destructive avalanche.
Weather Forecast
Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1800 metres with alpine temperatures of -3.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1800 metres with alpine temperatures of -3.Monday: Cloudy with sunny periods and isolated flurries with a trace of new snow. Light southeast winds. Freezing level to 1700 metres with alpine temperatures around -3.
Avalanche Summary
Reports from Thursday showed storm slabs releasing from Size 1.5-2 with explosives triggers in the Revelstoke area. Loose wet avalanches were observed running from Size 1.5-2 in steep terrain with ski cutting and explosives. Slab crown fractures ranged from 10-60 cm and north to northeast aspects saw the majority of reported activity.Reports from Wednesday included one observation of a natural Size 2.5 wet slab that was triggered by a smaller loose wet avalanche. Loose wet avalanches were generally observed running to Size 1.5 from steep terrain, both naturally and with skier traffic.Several natural cornice falls up to Size 3.5 were reported on Tuesday in the Monashees and the Selkikrks. Natural cornice and one persistent slab avalanche up to Size 3.5 were reported from the Monashees on Monday. The persistent slab avalanche was triggered by a wind slab in steep terrain on a southwest aspect at 2400 metres. On Sunday natural cornice falls released up to Size 2.5, and one pulled an unsupported slope resulting in a deep slab release.
Snowpack Summary
Roughly 30-40 cm of new snow has formed fresh storm slabs on the surface after Thursday and Friday's snowfall. These new storm slabs developed above a mix of old surfaces that include melt-freeze crusts at treeline and below and on solar aspects in the alpine. In addition to storm slab formation, the new snow has also contributed to fragile new cornice growth. Cornices have been a primary avalanche problem in the past week, with recent reports of cornices falling off naturally with loading from wind, or due to warming from direct sun or daytime heating. The February weak layers are now down about 170-220 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These deep weak layers have recently produced large avalanches with large triggers like cornice falls, and they may be more likely to fail on southerly aspects during periods of strong solar radiation.
Problems
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.
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.