Be wary of any slopes receiving direct sun. Solar warming could trigger avalanches or weaken existing slabs.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Friday
Weather Forecast
Thursday: Light snow. 5-10cm. Light to moderate south-west winds. Freezing level at valley floor.Friday/Saturday: Clear and sunny. Light winds. Afternoon temperatures rising on sunny slopes, with the freezing level falling to valley floor at night.
Avalanche Summary
On Tuesday, little activity was reported, except a size 1 storm slab which was triggered by a skier. On Monday, natural avalanches up to size 3.5 failed on southerly aspects down about 100-150cm on the mid-February persistent weak layer. Avalanches releasing on this layer are becoming less frequent. Solar warming is of particular concern over the next few days, as it could destabilize storm slabs and cornices, potentially initiating deep failures on the mid-February layer. Be particularly wary of sunny aspects during the heat of the day.
Snowpack Summary
15-30cm of recent storm snow overlies various surfaces including settled snow, wind slabs and crusts. New wind slabs have formed in the alpine and at treeline. Sunny breaks on Sunday caused moist snow up to about 2400m on solar aspects and up to about 1500m on all aspect. Cornices have grown large and unstable. The new snow has added to the well consolidated storm slab that overlies weak surfaces that formed early February. This interface, which lies 1-2m below the surface, includes a widespread surface hoar instability that, depending on aspect and elevation, may exist in combination with facets or crusts.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.