Regions
Northwest Inland.
New snow may be hiding old wind slabs. Watch out for lee features even if there aren't obvious signs of fresh wind loading.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SUNDAY: flurries overnight becoming light snow through the day with total accumulations of 5 to 10cm expected, light southerly winds, 1000m freezing level. MONDAY: flurries continue, light westerly winds, 1000m freezing level. TUESDAY: flurries continue overnight before clearing through the day, light easterly winds, 1000m.
Avalanche Summary
Numerous small wind slabs were reported in the Alpine from the north west of the region, were recent snow fall amounts were greatest. Below treeline warm temperatures triggered a widespread loose wet avalanche cycle and glide crack releases on Friday.
Snowpack Summary
Recent snow has been heaviest in the west and north of the region, creating new wind slabs in the alpine and at treeline. The new snow sits above old wind effected snow, a crust on sunny aspects or surface hoar in isolated sheltered and shady locations. A rain crust may be found on the surface at lower elevations. In general the upper snow pack is reported to be bonding well to a crust buried on February 12th, now 40 to 80cm down, that extends up to around 2000m. The early January surface hoar can be typically be found between 60 and 140cm down. Although it is getting harder to trigger in most places this layer it remains a concern, especially in the north and east of the region. Shallow snowpack areas also have a weak base layer of facetted snow 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.