Avalanche control work today on Parker Ridge today confirmed that triggering a large slab with a light load is quite possible. With isolated natural activity observed today as well, it is clear that the stakes are starting to rise...
Weather Forecast
Saturday will see continued cool temps with cloud and the potential for light flurries. On Sunday a SW flow will bring 5-10cm of precipitation with winds increasing to moderate SW and temperatures rising into the -10C range.. Significant snow may arrive Monday as temps peak at -5 C in the alpine.
Snowpack Summary
Persistent slabs sit above 3 weak interfaces in the top 30 to 50cm of the snowpack. Depth and distribution of these weak surface hoar/facet layers varies with the terrain and vegetation shelter, but they are consistently found in sheltered features at TL and above. Windslabs have developed in open areas TL.
Avalanche Summary
Natural windslab avalanches up to size 1.5 were observed Tuesday in windswept alpine moraine features. These events appeared to be running on the persistent slab interface down 30 to 50cm.
Confidence
Intensity of incoming weather systems is uncertain on Sunday
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.