A persistent weak layer (PWL) of faceted snow and surface hoar that formed during the mid-November dry spell has been buried underneath snowfall and wind-drifted snow over the past two weeks. Avalanches have been failing on this PWL, breaking down 2-4' deep (or deeper) and over 100' wide (and wider). Although the PWL is present on all aspects and at all elevations, it is most pronounced on mid and upper elevation aspects facing northwest through north and east. Moderate to strong winds overnight and into today may drift snow onto these aspects, creating an additional load and further stressing this buried PWL.

You may get warning signs of instability such as loud collapses and cracking, but persistent weak layers are also notorious for not providing these obvious clues of instability, and instead wait for the 2nd, 5th, or 15th rider on the slope before avalanching. These avalanches may be triggered remotely (from a distance) and may also allow you to get well onto a slope before fracturing far above you.

The strategy to avoid getting involved in one of these large and dangerous avalanches is to not travel on, below, or adjacent to slopes 30° or steeper on aspects facing northwest through north and east. Fortunately, cold temperatures and regular snowfall are providing great riding conditions on low-angled slopes on all aspects.