Watch for deep and touchy pockets of wind slab in wind exposed terrain.
Weather Forecast
The ridge of high pressure rebuilds and should result in clearing skies in most parts of the Province. However, there is a weak cold front sliding in from the east that could bring cloud and light snow to parts of the Southern Interior (particularly the east side of Purcells). By Sunday all regions should be enjoying sunny skies. The freezing level on Saturday is 500-1000 m and it bumps up a couple hundred metres each day. Ridge winds are light gusting to moderate from the NW to NE.
Avalanche Summary
Avalanche activity has gradually tapered off throughout the week. On Thursday explosive control work on steep North and East facing slopes only resulted in loose snow sluffs. Earlier in the week there were reports of natural and explosive triggered cornice falls and slabs, typically size 2-3 and all from alpine terrain.
Snowpack Summary
A light dusting of new snow covers the previous variable snow surface of crusts, surface hoar, dry facetted snow, or wind affected snow depending on aspect and elevation. Thin new wind slabs are likely in exposed lee terrain, and cornices remain large and weak. The 'Valentine's Day' crust is thick and supportive below 2100 m. The late-Jan crust/surface hoar layer is 1-2 m deep in the west, and can be found within the upper metre of the snowpack further east. It is variably reactive in snowpack tests and still the main concern in many areas. The mid-January surface hoar, deeper again, remains problematic in some areas. The mid-December and mid-November weak layers of crusts and facets can still be found near the bottom of the snowpack, particularly in shallower eastern parts of the Purcells.
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.
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.