At the mid and upper elevations, unstable slabs lie upon faceted snow and hard crusts. These slabs have become slightly less sensitive and are not releasing remotely as they were two days ago. Even so, conditions remain VERY DANGEROUS. The persistent slab problem continues to exist and slabs can still release on any aspect with the weight of a single person. These slabs can be small, involving wind loaded features or very large, involving entire bowls. Analysis of both terrain and snowpack is essential today and making conservative decisions could save your life. The persistent slab problem also extends into the upper portion of low elevations where smaller slabs lie upon surface hoar on northerly terrain.
Large slab avalanches are likely to be human triggered on a variety of aspects above an elevation of 7,000 feet. Generally, these slabs have depths of two to three feet, however in some high elevation terrain, they could have depths to as high as five feet.
The next system is to arrive tonight and continue through Friday. Nearly a foot of new snowfall is expected in the higher elevations by Friday evening. Temperatures are to warm through this period with mountain temperatures reaching the upper twenties in the afternoon. Winds from the southwest to west are to average between thirty and thirty-five miles per hour. This system is to have a greater impact on the northern forecast areas, where the National Weather Service has issued a Winter Storm Warning. Snow is also expected in the valleys although periods of rain could occur during the afternoon as above freezing temperatures are forecast. The predicted heavy snowfall, strong winds, and increasing temperatures will present two avalanche concerns. New wind slabs will start to form on existing snow surfaces, which is loose, settled snow in most areas although wind packed surfaces and thin sun crusts can be found. These slabs will develop though out the day and are expected to be relatively small. A much greater threat lies with existing persistent slab problem. New snow will add load on these weak layers and slabs running on these crusts and faceted grains are expected to increase in both size and sensitivity throughout the day. These DANGEROUS slabs could be triggered by a single person. The rating is expected to be Considerable above 7500 and Moderate below that elevation.
