Confidence
Good - Due to the quality of field observations
Weather Forecast
An upper trough will attempt to penetrate the upper ridge today over the province. Protions of it will ride southward through the province late on Wednesday bringing light to precipitation to south central BC. The ridge will rebuild for Thursday and Friday with temperature inversions and light winds.Wed: Flurries, with a trace of precipitation, light winds, freezing level to 1600M.Thursday: Nil Precip., light ridgetop winds, freezing level to 1600m.Friday: Nil precip., sun and clouds, ridge top winds light , freezing levels rise to 2300m.
Avalanche Summary
No reports of recent avalanche activity. Areas of shallow snowpack are of special concern right now, as well as areas where there is a hazard from above such as cornices or steep south facing cliffs. High temperatures at upper elevations may increase the chance of triggering from surface sloughing or cornice failure.
Snowpack Summary
Extensive wind transport and wind slab development has occurred in all areas of the region. Recent storm snow varies from 40-70 cm across the region and in some alpine areas storm slabs are more than a metre thick. Persistent weak layers of buried crusts/facets/surface hoar continue to be a concern, and are suspected to have been the failure plane for recent large natural avalanches. Surface facetting and surface hoar growth throughout the forecast region on northerly and protected aspects. Strong solar radiation and above-freezing temperatures producing sun crust on solar aspects.
Problems
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.
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.
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.