The weak mid pack will take some time to stabilize. Fresh snow loading, either by wind or new snow, will tip the scales towards an avalanche cycle. Avoid large terrain while the snowpack adjusts.
Weather Forecast
Snow beginning Thursday afternoon or evening bringing 10 cm. The winds will continue overnight tonight, but taper slightly as the incoming weather passes. Expect SW winds at 40km/hr in the alpine tomorrow. Temperatures will range from -8 at the road to -10 at ridge top.
Avalanche Summary
One slab was noticed today below a large alpine cliff face. Sz 2(estimated, debris pile was not seen), E asp, 2500m. From a distance it looked about 60cm deep and 100m wide. Likely ran on the Dec 18th facets.
Snowpack Summary
The steady winds that we've been experiencing lately are significantly changing our snowpack. Windslabs are the current problem at the forefront of our minds. We are starting to see them even below treeline, however they are of little concern as there is still very little snow at valley bottom. Open areas at treeline is where the slabs start to become a legitimate concern. At the moment, the slabs as a whole are up 40cm thick. This thick layer is actually made up a series of laminated slabs from various wind events. These slabs are sitting on a delicate layer of facets that were buried on Deb 18th. This facet layer is widespread and will likely last for weeks to come. Snow depth at treeline was 125cm today. The alpine has a similar condition in terms of windslabs and weak layers underneath. We are finding the Dec 18th facets alive and well in most areas. In thinner snowpack areas, these facets are more pronounced and have turned into depth hoar. The snow coverage is variable with dramatic transitions. It will go from gravel to a meter deep snowpack in only a few steps. Wind loaded areas will have a surprising amount of snow in them.
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.