Afternoon cloud reduced the effects of the sun yesterday. Today should be mostly sunny- which will increase danger. Cornices are the biggest concern right now; they are large and weak, and likely to fail with the strong sun.
Weather Forecast
Lots of sun, warming temperatures, and calm to light SW winds are expected today and Monday. High cloud may form this afternoon and reduce solar inputs. Solar aspects, starting with easterly in the mornings, will receive strong solar. By Monday, air temps will be closer to 0'C and the effects of the sun will be greater. Clouds will increase on Tues
Snowpack Summary
Cool temps and clouds have reduced solar effects; a sun crust has formed only on steep, solar aspects. Elsewhere, 25cm of dry snow exists above 1400m. Tests on two 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
Natural avalanches were triggered during sunny breaks yesterday. 7 size 2 to 2.5 avalanches were observed mid day from solar aspects. Many were loose, with moist debris and a few triggered slabs. Very large cornice failures were reported throughout the Selkirks yesterday. One cornice failure was reported to be 120m long and triggered a size 4!
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.