Regions
Northwest Inland.
A moderate series of storms will raise avalanche danger for Sunday and again for Tuesday.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Sunday: 5-10 cm new snow expected, with the freezing level around 700 m. Winds are expected to be moderate to strong, gusting 40-60 km/r at ridgetop, getting stronger later in the day. Monday: A short-lived break during the day, possibly accompanied by some flurries. Freezing level around 800 m, winds strong in the morning, becoming light southwesterly. Monday night and Tuesday: a weak storm is expected to start late on Monday, bringing around 5 cm Monday night, and another 5 cm or so on Tuesday. Freezing levels around 900 m, winds strong southwesterly.
Avalanche Summary
No new avalanche observations.
Snowpack Summary
Continued snowfall and mostly southwest New wind slabs are developing in the lee of of southwest winds in the alpine and at treeline. Storm snow from last week has settled due to recent warm temperatures. There may be a buried layer of surface hoar in the top 30 cm of the snowpack from early February, this layer was found at Hankin, but has not been widely reported. Crusts may be developing at mid-elevations as the freezing level slowly descends. The early January persistent weak layer of buried surface hoar is down 50-80 cm in most of the region, but may be down a metre or more in the deeper snowpack areas in the southwest of the region. Shallow snowpack areas in the east and north of the region may have a weak base layer of facetted snow on or just above 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.