Rapid loading by snow and wind are forecast later today. Minimize your exposure to avalanche terrain during the storm, including while traveling across paths in the valley bottom. Avalanches have been running fast and far onto avalanche fans.
Weather Forecast
A cold front will pass through the region today. Moderate precipitation rates, with ~8cm accumulation today, mild temps and moderate to strong westerly winds are forecast. These are ideal slab formation conditions. Over the weekend expect mostly cloudy skies, light flurries, and light winds shifting to the NW at ridgetop.
Snowpack Summary
~45cm storm slab sits on a weak layer of large snowflakes which are reactive in tests. The Dec 8 PWL, which is surface hoar at lower elevations and facets and variable wind slabs at higher elevations, is down ~80cm. This layer is becoming less reactive in tests. The Nov 28 surface hoar, down ~1m, is still reactive where it exists.
Avalanche Summary
Recent avalanche activity has been triggered by rapid loading by snowfall and wind-loading, with avalanches to size 2.5 running into avalanche fans.
Confidence
Intensity of incoming weather systems is uncertain
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.