Several surface hoar layers in the upper snowpack are sensitive to human triggering. A small avalanche could initiate a deeper instability resulting in a large avalanche.Avalanches from the Alpine have the potential to reach Valley Bottoms.
Weather Forecast
Today will be a lull between storms, with the next notable amount of snow coming in Tuesday evening into Wednesday. Today you can expect cloud and sunny breaks with periods of light snow. Freezing level to remain at valley bottom with and Alpine high of -8. Winds at ridge top will be 20-35km/hr from the southwest.
Snowpack Summary
17cm of snow overnight, ~50cm of storm snow sits atop the January 16 surface hoar layer which is settling quickly and reactive in tests. The December 15 surface hoar is down 100cm and is highly visible in profiles and still producing sudden planar results in tests. Strong south winds have built pockets of wind slab in the Alpine.
Avalanche Summary
Several natural avalanches size 2-3.5 yesterday. The size 3.5 dusted and spread small woody debris on the highway for a 100m section.Avalanches originating in the Alpine have the potential to run into valley bottoms.
Problems
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.