Confidence
Fair - Due to variable weather conditions
Weather Forecast
Wednesday-Friday: Moderate to strong north-westerly winds. Freezing level is at valley bottom, with alpine inversions possible (parcels of warm air which could bring alpine temperatures close to 0). Light snow is possible on Wednesday.
Avalanche Summary
Avalanche activity has begun to slow, but occasional skier-triggered avalanches are still being reported, failing on persistent weak layers from early January. Many of these events were on SE through SW aspects, with the odd persistent slab on other aspects. Some solar-related and loose dry natural activity was observed on Monday.
Snowpack Summary
North to north-westerly winds have left wind slabs in the lee of terrain breaks such as ridges and ribs at alpine and treeline elevations. Recent storm snow is settling over old snow surfaces including surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of these weaknesses is patchy, but where they exist, it is still possible to trigger a large avalanche with the weight of a person or snowmobile. Watch out for rapid warming on alpine slopes over the next couple of days, which could weaken the slab above these interfaces. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.
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.