Wind slabs continue to be reactive at upper elevations. A persistent slab problem still exists at lower elevations and has been responsible for occasional human-triggered avalanches.
Weather Forecast
TUESDAY NIGHT - Clear periods / southeast winds 20-35 km/h / alpine low temperature near -12WEDNESDAY - Cloudy with sunny periods / southeast winds 10-25 km/h / alpine high temperature near -6THURSDAY - Flurries, 5 cm / southwest winds 10-25 km/h / alpine high temperature near -7FRIDAY - Cloudy with scattered flurries / west winds, 15-25 km/h / alpine high temperature near -10
Avalanche Summary
Reports from the past couple of days show a continuation of wind slabs reacting to ski cuts, with a trend toward smaller (size 1) releases. Small (size 1-1.5) loose dry avalanches have also been observed releasing naturally from steeper, sun exposed slopes in recent days.Reports of human triggered persistent slab avalanches on the January weak layers have been on the decline, suggesting these layers have evolved into a lower likelihood avalanche problem, but one that still requires a measure of discipline to manage effectively.
Snowpack Summary
Weeks of mainly dry, windy, and cold weather have transformed the snowpack at upper elevations into a mix of wind-affected surfaces and wind slabs on all aspects. These wind slabs have shown prolonged reactivity because they are sitting on facets (sugary snow).There are a couple of prominent weak layers in the upper snowpack that were buried in mid and late January. These can be found approximately 40-80 cm deep. Both layers consist of surface hoar (feathery crystals) and may be associated with a crust on steep, south facing slopes. These weak layers have been most reactive at lower elevations, and especially below treeline.The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the snowpack.
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.