Confidence
Fair - Intensity of incoming weather is uncertain on Wednesday
Weather Forecast
Wednesday: Snow amounts up to 15cms. Ridgetop winds 70-90km/hr from the West. Freezing levels should remain at valley bottom. Thursday/Friday: A ridge will build over the coast bringing mainly dry conditions. Few flurries expected up to 5cms. Freezing levels will remain at valley bottom during the day then start to rise in the evening. Ridgetop winds 50-70km/hr from the NW.
Avalanche Summary
Explosive avalanche control have produced slab avalanches up to size 2, @1900m and above on W-N aspects. With forecast snow and wind, we can expect to see a continued avalanche cycle.
Snowpack Summary
An additional 20cms accompanied by strong Southerly winds is forming new wind slabs and storm slabs on the upper snowpack. The upper 50-70cms of the snowpack is resting on a variety of older snow surfaces. These surfaces include previous cold, dry low density snow which may have had seen some faceting, old wind slabs, and crusts. Reports indicate it may be particularly reactive between 1700 and 1800m where a rain crust lies buried approximately 30-50 cm below the snow surface. 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
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.