Regions
Northwest Inland.
Strong outflow winds have created touchy wind slabs that are likely easy to trigger. Watch out on solar aspects where the sun could weaken the snow surface.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
TUESDAY: Sunny, light to moderate northerly winds, alpine temperature near -12 C, freezing level below valley bottom.WEDNESDAY: Partly cloudy, moderate to strong northerly winds, alpine temperature near -10 C, freezing level below valley bottom.THURSDAY: Partly cloudy, light to moderate westerly winds, alpine temperature -9 C, freezing level below valley bottom.
Avalanche Summary
Many small to large (size 1 to 3.5) wind slabs were reported on both Saturday and Sunday in lee features and cross-loaded terrain on southerly to easterly slopes. The avalanches were triggered naturally and by skiers.Avalanche activity may slow down with a period of cold, clear weather expected to persist well into the week, unless the sun is powerful enough to warm the snow surface. 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 at all elevations.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.