Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Synopsis: A strong frontal system is forecast to reach the South Coast late on Sunday bringing heavy snow and strong winds. Conditions should be unsettled in the wake of the system with flurries and occasional sunny breaks. Sunday: Periods of snow, heavier in the evening and overnight. 25-40 cm by Monday morning. Winds increasing to strong from the SW-SE with the arrival of the system. Freezing level around 500 m. Monday: Snow easing to flurries and possible sunny breaks. Around 5 cm. Freezing level remains around 300-500 m. Tuesday: Cloudy with flurries. Freezing level near valley bottom.
Avalanche Summary
Recent activity has been limited to a few small (size 1) soft slab avalanches in immediate lee features and small loose snow avalanches in steep terrain. Observations from early last week included several old size 2-3 avalanches, primarily from northerly aspects in the alpine. These events may have released on a weak layer of surface hoar, now down over a metre deep.
Snowpack Summary
Several potential weaknesses may exist within or under the new storm snow, including one or two surface hoar layers and a sun crust. Recent winds have been stiffening the low density storm snow and forming reactive slabs in exposed lee terrain. Below the recent storm snow weaknesses, the snowpack is well settled and strong. A layer of surface hoar that formed during late November has been found intact or decomposing in some locations down a meter or more. The early November crust/facet combination near the base of the snowpack seems to be dormant, at least in deep snowpack areas where it is buried too deeply by a stiff snowpack to be affected by light triggers on the snow surface.
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.