Persistent slab avalanches continue to pose a low likelihood, high consequence problem at lower elevations.
Weather Forecast
SUNDAY NIGHT: Clear, light northeast wind, alpine temperatures drop to -20 C.MONDAY: Sunny, light northeast wind, alpine high temperatures near -12 C.TUESDAY: Sunny with cloudy periods, light northeast wind, alpine high temperatures near -8 C.WEDNESDAY: Cloudy with isolated flurries, light southeast wind with moderate gusts, alpine high temperatures near -10 C.
Avalanche Summary
A few small (size 1) wind slab avalanches and loose dry sluffs were reported over the weekend. On Friday, numerous natural, human, and explosive triggered storm slabs (size 1-2) were reported during the storm.
Snowpack Summary
20-40 cm of low density snow is gradually settling and has potentially blown into wind slabs in exposed terrain. The snow sits on older wind slabs at upper elevations, which will be difficult to detect now that they are buried. In sheltered areas and below treeline, the new snow sits on facets (sugary snow) and surface hoar (feathery crystals), and a crust on south-facing slopes.There are potentially three layers of surface hoar in the top 100 cm of the snowpack. One is down 30-50 cm, another is down 40-80 cm, and the last one is down 80-110 cm. These layers have been most prominent and reactive between 1600-1900 m.The lower portion of the snowpack is generally strong.
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.