Check out the latest Forecaster's Blog post below.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Monday
Weather Forecast
Monday: Mainly sunny. Cloud increasing and snowfall starting in the evening. Light winds. Tuesday: Moderate to heavy snow. Freezing level near 400m. Strong south-westerly winds.Wednesday: Scattered convective snowfall. Light winds.
Avalanche Summary
Last week was very active with natural avalanche activity, human involvements and close calls. Some were failing on the mid-February persistent weakness. The size and frequency of avalanches seems to have decreased slightly over the weekend as storm slabs and wind slabs slowly gained some strength. On Sunday, avalanches were triggered naturally and by explosives in steep, rocky terrain to size 2. Avalanche activity may increase again with solar warming on Monday, or with snow and wind on Tuesday.
Snowpack Summary
Last week, 100-180 cm storm snow fell, accompanied by strong south-easterly to south-westerly winds. Storm slabs and wind slabs now appear to be slowly gaining strength. Cornices are large and threaten slopes below. A persistent weakness, formed in mid-February, continues to produce hard, sudden planar results in snowpack tests. The likelihood of triggering this layer has gone down, but very large avalanches remain possible, which could be triggered by a shallower avalanche or cornice fall. The average snowpack depth at treeline is 350 cm.
Problems
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.
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.