Regions
Northwest Inland.
Wind slabs linger at higher elevations -- best to stick to sheltered terrain. Watch out on solar aspects where the sun could weaken the snow surface.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
WEDNESDAY: Cloudy early morning with trace snowfall then mostly sunny, moderate to strong northerly winds, alpine temperature near -12 C, freezing level below valley bottom.THURSDAY: Partly cloudy with increasing cloudiness, light to moderate westerly winds, alpine temperature -7 C, freezing level below valley bottom.FRIDAY: Cloudy with early-morning snowfall, accumulation 2-5 cm, light to moderate westerly winds, alpine temperature near -8 C, freezing level near 400 m.
Avalanche Summary
On Monday, a small wind slab was skier triggered that scoured down to the basal sugary faceted snow in a thin snowpack area, around 60 cm in thickness. This occurred on a southerly aspect around 2000 m in elevation.On Saturday and Sunday, many small to large (size 1 to 3.5) wind slabs were reported in lee features and cross-loaded terrain on southerly to easterly slopes. The avalanches were triggered naturally and by skiers.Avalanche activity may increase with warmer air temperatures and if clear skies prevail. Watch for steep sunny slopes due to the suns influence, lee features for reactive wind slabs, and be extra cautious near thin spots and shallow snow pack areas where triggering a deeper weak layer is more likely.
Snowpack Summary
Northeasterly winds have created stiff wind slabs on leeward slopes and scoured wind-exposed slopes. The cold temperatures are helping to break down these wind slabs, but they will likely remain reactive to light and heavy loads where preserved.Deeper in the snowpack, two layers of crust and/or weak surface hoar are 20 to 40 cm deep and 60 to 100 cm deep. The deeper crust exists well into the alpine and the surface hoar can be found in sheltered areas in lower alpine and tree line elevations. Snowpack tests have produced hard, sudden results on weak, sugary snow crystals associated with this deeper crust in the Smithers area, suggesting that it is a layer of concern.
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.