Avalanche danger will increase through the day on solar aspects. Avoid exposure to cornices and slopes that have been receiving direct sun.
Weather Forecast
Lots more sun is forecast for today and Tuesday. Cool temps are helping to reduce solar effects; alpine temps should stay below -10. Light alpine winds are forecast, but down-flow winds off glaciers are creating areas of windeffect. Freezing levels and alpine temps will start to rise over the next 3 days. Increasing cloud is expected on Wed.
Snowpack Summary
On steep, solar aspects the surface becomes moist and loose with warming, freezing into a crust overnight. 25cm of dry snow exists above 1400m elsewhere. Tests on surface hoar/crust layers in the top 1.5m indicate that they may be triggered by large loads (like cornices) in some areas (most likely on solar aspects). The snowpack below is strong.
Avalanche Summary
Yesterday, skiers triggered a size 2 on a W aspect at 2585m at 2pm. The avalanche failed on surface hoar sitting on a sun crust. The slab was 25cm deep, 100m wide and 120m long. Tragically, one person was fatally buried 1.9m deep. Natural avalanches were triggered on solar aspects and large cornice failures were reported throughout the Selkirks.
Confidence
Intensity of incoming weather systems is uncertain
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.
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.
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.