Elevated danger ratings will persist, especially with forecast warm temperatures. If solar radiation is strong the avalanche danger may exceed posted levels.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
The current dry ridge of high pressure will break down somewhat allowing for increased cloud and isolated flurries on Wednesday evening. The ridge is expected to rebuild on Thursday with mainly clear skies before an upper trough bring light snowfall on Friday. Winds should remain light with moderate gusts from the west/northwest. Freezing levels should hover around 1800m on Wednesday, 1700m on Thrusday, and about 1500m on Friday.
Avalanche Summary
On Monday explosives control produced storm and deep persistent slab avalanches to size 3.5 which occurred on all aspects at treeline and above. On the same day a splitboarder triggered a size 2.5 storm slab on a west aspect in the Revelstoke area. No injuries were reported. In the southeast corner of the region a vehicle remotely triggered a size 2.5 slab avalanche from the ridge above. The February 10th interface was responsible for this event.Last Saturday's avalanche fatality occurred in the Keefer Lake area northeast of Cherryville. The avalanche, which occurred in a cut block at about 1700m, involved 3 sledders who were in a party of 6. 2 of the men were able to inflate their airbags and were partially buried. The deceased was reportedly not able to inflate his airbag, and was buried approximately 5m below the surface.
Snowpack Summary
In some areas over 80cm of recent storm snow overlies small surface hoar in sheltered areas and a sun crust on previously sun exposed slopes. In wind exposed terrain these new accumulations have been pushed into much deeper deposits by generally moderate southwest winds. The recent storm snow may be particularly reactive in high elevation lee terrain or on sun-exposed slopes where it likely overlies the buried crust. Low elevation terrain and sun-exposed features are likely seeing a daily melt-freeze cycle. At ridgetop cornices are large, unsupported and waiting for the right trigger.The mix of weak surfaces which were buried on February 10th is still reactive. This persistent interface lies between 100 and 200cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. This deeply buried layer continues to fail with remote triggers in isolated terrain. Likely triggers include a surface avalanche in motion, a cornice fall and solar radiation.For the most part, the mid and lower snowpack are strong and well consolidated.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.