Regions
Northwest Coastal.
Thursday's storm could be enough trigger a widespread natural avalanche cycle. We could see surprising avalanches in "safer" area like lower angle and forested slopes. Keep your guard up.
Weather Forecast
Tonight and Thursday: 15-25 cm of snow. The freezing level is 600-1000 m. Winds are strong from the South. Friday: Cloudy with flurries. The freezing level is near 600-800 m and winds are moderate from the SW. Saturday: Mainly cloudy. The freezing level is near valley bottom (or 500 m) and winds ease to light.
Avalanche Summary
Numerous avalanches were reported in the region on Monday and Tuesday. Reports included widespread activity up to size 2 north of Stewart and a natural avalanche cycle up to size 3.5 northwest of Terrace. Several skier triggered avalanches and remotely or sympathetically triggered avalanches up to size 2 were also reported. Most recent avalanches released on the Jan 9 surface hoar layer down 30-80cm. The majority of these avalanches were reported on north aspects, but there were avalanches on all aspects and elevation bands.
Snowpack Summary
Recent storm snow amounts have been variable across the region, but generally 40-60cm have accumulated since January 9th when the most recent surface hoar was buried. Below that is another surface hoar layer down 60-80cm. Remote triggering, whumpfing, and sudden "pops" shears are all indications that both these layers could propagate well if triggered. Deeper persistent weaknesses buried in December have the potential to wake-up to heavy loading, rapid warming, or avalanches stepping-down. Recent strong southeast winds have loaded leeward features on west through north aspect slopes, and scoured leeward slopes.
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.