While the early season snowfall was welcomed by all of us who like to play in it, the recent cold snap has wrecked some havoc with it.  Many areas of the Cascades and Olympics have experienced and are experiencing significant faceting...both above a slightly decomposing mid-upper pack crust (near surface facets) and below the crust all the way to the ground.  This is just beginning to create intermediate faceting, not depth hoar yet,  for most Cascade west side areas, but the generally shallower Cascade east slope snowpack is dominated by facets and quite sugary with some true depth hoar (well developed columnar shapes) likely near the ground.

In general faceting occurs most quickly when air temps are close to freezing since the vapor pressure is highest there and thus there is more vapor to be deposited or transferred as new facets.   The change in vapor pressure per degree temperature change is highest at these temperatures, hence facets or depth hoar develop near the ground where it's normally close to freezing. This gradient in the snowpack is by no means static or average, with maximum temperature gradients often above higher density layers like crusts (the crust conducts the heat well, but the lower density snow above the crust does not = high gradient).  Below crusts, the vapor is deposited because it accumulates (it has nowhere to go since the crust provides a cap).  The end result is that the near-surface facets and surface hoar will provide plenty of weak layers that may linger for some time.

With the more normal Cascade loading that we have seen recently, and are likely to see more of, we can expect the development of slabs (and the resulting sympathetic fractures, remote triggering, cracking and whumpfing).   The combination of slabs and weak layers is, as many of you know, what results in dangerous avalanches.  In areas where a shallower and more faceted snowpack exists, there could be climax slides to ground.

The take home message...be careful and aware that weak layers have developed and could linger for some time.