Weather Forecast
Monday: 10-15cms of new snow. Ridgetop winds 50-75km/hr from the SW. Freezing levels near 800m. Treeline temperatures near -3. Tuesday: A major system is arriving bringing heavy precipitation (40-50mm), and rising freezing levels near 2000m. Ridgetop winds 75km/hr from the SW. Wednesday: Heavy precipitation will continue (25-35mm). Freezing levels 2000m will start to fall back to 800m early Wednesday into Thursday.
Avalanche Summary
A natural size 2 avalanche occurred on a N aspect at 2000m below a cornice feature on shallow, rocky terrain. Natural small (size 1) avalanches occurred on wind loaded features above 1800m, while skier controlled touchy wind slabs were reactive between 1700-1800m. Numerous size 1-2 explosive triggered avalanches were reported with wide propagation. With forecast snow and wind, we can expect to see a continued avalanche cycle.
Snowpack Summary
New snow up to 40cms accompanied by strong SW winds has formed into a cohesive slab on previous, low density cold snow. Reports indicate it may be particularly reactive between 1700 and 1800m, although I would be concerned about this interface on all steep terrain right now. A rain crust lies buried approximately 30-50 cm below the snow surface at lower elevations (up to around 1800m). Reports indicate the bond at this interface is quite good, although the slick nature of the crust may still provide a sliding layer in some steeper locations. This may be a layer of concern with forecast wind, snow and rising freezing levels to come. Previous concerns about deeper persistent weak layers appear to have diminished. Snowpack depths at treeline are in the region of 260 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.