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 1500m on Wednesday, 1400m on Thrusday, and about 1600m on Friday.
Avalanche Summary
On Monday evidence of a natural avalanche cycle to size 3.5 was observed. The activity likely occurred on Sunday with many of the avalanches releasing on the February 10th interface. Large cornice fall was also reported in the region. A report also came in about a close call on Sunday. A ski touring party had 1 partial burial and a full burial by what sounds like a size 3.5 avalanche in the Ozalenka Valley south of McBride. The slab thickness was about 100cm and the avalanche covered about 8 hectares. Everybody walked/skied away from the incident.Looking forward, more natural activity may occur on solar aspects with forecast sunny breaks and warming.
Snowpack Summary
Up to 80cm of snow fell over the past week. This storm slab overlies small surface hoar crystals in sheltered areas and a sun crust on previously sun-exposed slopes. The storm snow may be strengthening somewhat, although it may continue to be reactive in wind exposed terrain or where it overlies the buried crust. Low elevation terrain and sun-exposed slopes are likely seeing a daily melt-freeze cycle. Cornice development has also been significant.There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies about a metre below the surface, and includes weak surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Potential triggers at this point include a surface slab in motion, a large cornice fall, or intense solar warming.For the most part, the mid and lower snowpack are strong and well consolidated. Weak basal facets exist in some areas, but triggering is unlikely.
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.