Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
A series of systems will be crossing the Southern part of the province through the forecast period. Most of the punch will be in the South, but the Cariboo's will see light- moderate precipitation amounts, and a dominating SW flow with above normal temperatures. Tuesday: Snow amounts 2-5 cm. Ridgetop winds light from the South. Treeline temps near 2 degrees. Freezing levels 1700 m. Wednesday: Snow amounts 5-10 cm. Ridgetop winds moderate from the SW. Freezing levels 1200-1400 m overnight, rising to 1600 m during the afternoons. Thursday: Light-moderate snow amounts. Ridgetop winds mod-strong from the SW. Freezing levels 900 m.
Avalanche Summary
On Monday a size 2.5 natural cornice fall triggered the slope below. This was at 2400 m, on a North aspect. On Sunday, a size 3 natural, solar induced slab avalanche was reported from the Miledge Creek area. This ran in steep, unsupported terrain. No other observations reported. On Saturday three, size 3 natural avalanches were observed in steep, rocky, unsupported terrain. They occurred between 2000-2800m on north to east aspects and are suspected to have run on the February persistent weak layer.
Snowpack Summary
Recently formed wind slabs exist in the alpine and at treeline. Solar radiation has led to moist surfaces on sun exposed slopes with good crust recovery developing at night. Cornices have grown large and have become unstable; they may act as a large trigger on slopes below. A consolidated slab overlies a persistent weak layer that was buried in early February. Now 1-2 m below the surface, these weaknesses include surface hoar, facets or crusts. Concern still exists about the potential for deep and destructive releases at this interface. This may be a low probability, high consequence problem.
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.
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.
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.