Regions
South Coast Inland.
New snow and wind will keep the avalanche danger elevated at higher elevations on Thursday, especially in the south of the region where forecast snowfall amounts are the greatest.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Wednesday
Weather Forecast
Wednesday Night: 10-15cm of new snow / Moderate to strong southwest winds / Freezing level at 800mThursday: 3-5cm of new snow / Light southwest winds / Freezing level at 900mFriday: 8-10cm of new snow / Light southwest winds / Freezing level at 1200mSaturday: Light flurries / Light and variable winds / Freezing level at 1200m
Avalanche Summary
On Monday 2 people were buried in a size 2 slab avalanche in Marriott Basin in the Duffey Lake area. The touring party was large and all victims were rescued successfully by their partners, but all gear was lost. Not much is known about the aspect, elevation or the weak layer associated with the avalanche.Looking forward, new snow and wind on Wednesday night is expected to promote a new round of wind slab activity in higher elevation lee terrain.
Snowpack Summary
Monday's continuing storm brought 20-40 cm of new snow to the surface above about 1700 metres with depths that increase with elevation. The greatest accumulations occurred in the south of the region, and the snowpack at lower elevations is now capped by a new rain crust and only light new snow amounts. At higher elevations, strong southerly winds have redistributed the new snow forming deep deposits and cornices in leeward terrain. Storm snow totals since mid-January have reached about 150 cm.Below this depth, you'll likely find a few crusts that were buried during the first few weeks of January. Due to limited observations, not much is known about the current reactivity of these layers.The lower snowpack includes the more well-documented mid-December crust layer. Persistent slab avalanche activity from the Whistler area late last week suggests that heavy triggers like a large storm slab or cornice release may carry the risk of triggering this layer in isolated terrain - particularly in the north of the region where it has shown prolonged reactivity in snowpack tests.
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.
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.