Pay attention to alpine winds today. The stable conditions we have been enjoying may change rapidly due to SW winds loading lee slopes and forming new windslabs at and below ridgecrests.
Weather Forecast
A weak weather system will pass through the region today. Less than 5cm of new snow is expected, but winds will increase to moderate to strong from the SW. On Sunday, cool unsettled weather will continue with flurries and possible glimpses of sun. On Monday, a low pressure system will bring strong SW winds and ~10cm of new snow.
Snowpack Summary
Snowpack tests were conducted yesterday on N and SW aspects in the alpine. ~50cm of loose storm snow overlies a well settled snowpack. Tests found that the interface beneath the storm snow failed in with "easy to moderate" force but was resistant to move (RP). A surface hoar layer down 80cm and a crust down 1.5m would be hard to trigger.
Avalanche Summary
One new natural avalanche was observed along the highway. This size 2 loose avalanche was from a steep north facing alpine start zone affected by wind. Avalanche technicians traveling in the Illecillewaet and Asulkan drainages observed no new avalanches, nor did they experience any sluffing while skiing steep S and W slopes.
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.