Confidence
Fair - Forecast snowfall amounts are uncertain on Monday
Weather Forecast
Monday: Light to locally moderate snowfall / Moderate to strong southerly winds / Freezing level at 1200mTuesday: Light to locally moderate snowfall / Moderate to strong southwest winds with extreme gusts / Freezing level at 1200mWednesday: Mix of sun and cloud with a possibility of flurries / Light ridgetop winds / Freezing level at 800m
Avalanche Summary
In the Dogtooth Range on Friday, skiers initiated a cornice fall which triggered a size 2.5 slab avalanche on the slope below. In the same area on Saturday a size 2 slab was rider triggered from a ridge crest. A size 2 natural slab avalanche was observed on Saturday further south in the region. The February 10th interface is thought to have been the culprit in all of these events.
Snowpack Summary
Light amounts of new snow are expected to overlie weak surface hoar in sheltered areas, a sun crust on solar aspects and thin wind slabs in exposed terrain. These new accumulations are likely to be reactive as a wind slab in pockets of exposed terrain.The big news remains a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 50 and 120cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. Although natural avalanche activity has tapered-off at this interface, destructive avalanches are still a very real concern with ongoing reports of human triggering, whumpfing and sudden/easy snowpack test results. The mid and lower snowpack are generally strong and well consolidated. Weak basal facets exist in many areas, but triggering has now become unlikely.
Problems
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.
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.