Chad Brackelsberg
Executive Director
Snow that falls in fall and early winter can often become weak and faceted. This faceted weak layer, sometimes called depth hoar, produces large and deadly avalanches that kill more people in Utah than any other avalanche type. To ride in avalanche terrain we need to know where this weak layer of early season snow exists and where it doesn't exist. We want to choose slopes that don't have this weak layer.
To know where this weak layer exists so that we can avoid those slopes, we should take three steps.
- Identify the pattern of where this layer exists. In Utah, the pattern is usually driving by the direction the slopes face, the aspect.
- Once you're on snow, determine the aspect of the slopes where you're traveling. If the pattern follows other things like elevation, then identify that characteristic.
- Finally, verify whether this weak layer exists or not by digging into the snow. Choose a low angle slope (less than 30 degrees in steepness), with a similar aspect and elevation to the slope you hope to ski or ride, and dig into the snow to look for this weak layer. Ideally, if you've chosen terrain where you don't expect this layer to exists, you won't find it and you'll feel good about riding the slope in question.
All of this stuff can be confusing but with education, experience, and time you can learn it. The easiest option is always to choose low angle slopes where avalanches don't happen. Ride slopes less than 30 degrees in steepness with nothing steep above you, and you don't have to worry about avalanches. Of course, learning how to measure slope angles is another skill that takes time and practice to perfect.
Learn more about early season weak layers from Mark Staples' talk at the 2020 Utah Snow and Avalanche Workshop.