We’re excited to release an Avalanche Terrain Exposure Scale (ATES) map of the Crested Butte forecast area to help you with tour planning. ATES is a scale used to categorize the severity of avalanche exposure, strictly based on the landscape, regardless of snowpack conditions. The ATES scale classifies terrain into five categories based on slope angle, forest density, slope shape, terrain traps, avalanche frequency/magnitude, starting zone size and density, runout zone characteristics, interaction with avalanche paths, and route options for managing exposure. See the draft definitions of the five-level scale (V.2) below.
For this year-long project, we partnered with OnX and Beacon Guidebooks to categorize terrain around Crested Butte as Simple (Class 1 = Green), Challenging (Class 2 = Blue), Complex (Class 3 = Black), and Extreme (Class 4 = Red). We used an automated model approach called AutoATES, and calibrated the release areas and runout models using historical data from our avalanche records and local experience to tweak model inputs such as tree density and alpha angles. Although models are never perfect, the map should provide a useful resource for route planning and identifying what terrain is relatively more or less exposed to avalanche hazards. Remember that this map is independent of snowpack conditions; some days it is safe to travel in complex terrain, and other days it is dangerous. And you can still get into trouble in simple terrain under certain conditions. This map is available for free on our website here, or under the “Resources” tab on our website menu. Bookmark it as another tool! You can also use this map offline in the field using the OnX app (subscription required).