Regions
Northwest Inland.
Avalanche danger is higher in places where the recent storm dropped the most snow.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Saturday is expected to be cloudy with a few flurries. A front on Sunday brings light snow, moderate SW winds and cooling temperatures. Snowfall and winds ease on Monday.
Avalanche Summary
Isolated wind slab avalanches were reported over the last few days. Several large persistent slabs failed naturally in the north of the region last weekend. This weak layer was reported to be reactive to skier triggering from thin spots, as well as heavy triggers such as a smaller avalanches or cornice failures.
Snowpack Summary
Recent snow has been heaviest in the west and north of the region, creating new storm slabs and wind slabs. It also rained up to 1500 m in the south and 1000 m in the north on Thursday, so the low elevation snow surface is likely to turn into a crust once temperatures drop. The recent snow overlies widespread hard old wind slabs, scoured surfaces, a thin sun crust on sunny aspects, and surface hoar in isolated sheltered and shady locations. A melt freeze crust buried around February 12th, down about 50-80 cm, extends up to about 2000 m. A layer of surface hoar buried late in January remains a lingering concern. Shallow snowpack areas may also have a weak base of facets near the ground.
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.