Regions
Northwest Inland.
Confidence
Fair - Intensity of incoming weather is uncertain on Tuesday
Weather Forecast
Synopsis: A frontal system is moving across the area bringing light snowfall Monday night and into Tuesday. By Wednesday, a ridge of high pressure sets up, which should hold until Thursday afternoon.Monday night: 2-5 cm new snow overnight with strong SW winds and freezing level around 700m.Tuesday: Around 5 cm new snow, with strong to extreme SW winds gusting to 80km/h at ridgetop. Freezing level around 1100m.Wednesday: Dry and sunny. Freezing level falling to valley bottom. Moderate NW winds in the morning, diminishing through the day.Thursday: Dry, with cloud increasing through the day. SW winds starting light, increasing to moderate through the day.
Avalanche Summary
Loose snow avalanches were reported during the recent warm weather.
Snowpack Summary
Around 20-40cm recent new snow sits on a variety of old surfaces, which vary from facets to crusts and isolated pockets of surface hoar (sheltered treeline and below treeline). There is very limited information about the nature of the interface, with the only results suggesting reactivity in sheltered, shady treeline and below treeline slopes (preserved surface hoar). I would stress the importance of digging down to find and test weak layers.A strong mid-pack currently overlies a weak base layer of facets/depth hoar. It is worth noting that the snowpack in general is quite shallow compared to averages; triggering the basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.
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.