West Slopes South

Wind Slabs continue to be the most likely avalanche problem you’ll encounter on Saturday. Look for areas that look “fat” with pillow-like piles of snow, particularly on convex slopes or in confined gullies where triggering an avalanche is more likely. Buried weak snow has been identified in some areas of the zone and could lead to some surprising avalanches if activated.

It has been a generally stormy week around the West South zone, with several pulses of winter weather impacting the area, almost daily. While snow accumulations have been somewhat modest by Pacific Northwest standards around the zone, the winds have been constant. On Friday, NWAC forecasters near Crystal Mountain observed double cornice lines (indicating flip-flopping winds) and two fresh natural avalanches that were triggered due to cornices falling on the wind-loaded slope below. A similar story was relayed on Thursday from the Crystal area as well as the White Pass backcountry by avalanche professionals. 

This week, intact buried surface hoar was identified in the White Pass backcountry on a variety of aspects about 7" below the surface at mid-elevations. Additionally, in the neighboring Mt. Hood zone,  the same buried weak layer has been identified by NWAC forecasters in at least some locations. Given this information, it wouldn’t be a stretch to assume that it could be spread further south to the Mt. Adams and Mount St. Helens areas of our zone. On Friday, NWAC forecasters in the Crystal Mountain area were not able to find any buried surface hoar during their tour. That doesn't mean that it doesn't exist, but it is an encouraging thought. Additionally, we have not heard of any avalanches on this layer at this time, so there's no need to wave our arms about it. That said, we know it exists in the snowpack (at least at mid-elevations at White Pass) and as we incrementally load this layer a few inches of snow at a time, we could reach a tipping point resulting in avalanches. Slabs failing on buried surface hoar can break in surprising ways such as spanning far distances, breaking above you, or connecting/wrapping terrain features. If you experience whumpfing collapses, see shooting cracks, or see avalanches breaking in this manner, dial your terrain selection way back to avoid slopes over 35 degrees. 

White Pass was able to squeak out around 7” on 1/4, while other areas such as Crystal and Paradise received considerably less. Since then, an inch here and an inch there have been recorded by NWAC weather stations each day around the zone. Questions remain about storm totals on our southern volcanoes, and that same question will plague us moving into Saturday as another storm pulse rolls through the West South. The southern half of our zone and the volcanoes could once again be the outliers, receiving more snow accumulation and possibly some locally higher avalanche hazard. If you are traveling in one of these areas, be prepared to make your own observations, and then let us know what you find so we can paint a better picture for everyone.

At lower elevations, precipitation may come in liquid form in some areas. If you notice rain falling on dry snow, you could experience some rollerballs or other Wet Loose activity. In this case, if you start to see fan-shaped avalanches, simply head for lower-angled slopes. Any avalanche, whether wet or dry, wind or persistent should be confined to the snow above the easily identifiable Christmas Crust. We do not have any layers of concern below it at this time.