The Danger Rating, or Level, is a generalized description of the avalanche hazard. Danger ratings typically cover large, regional areas, where there is often significant variability in the hazard over the terrain. The avalanche danger rating is applied by elevation band, typically using the categories of Below Treeline, Near Treeline, and Alpine, or Upper Elevation, Middle Elevation, and Lower Elevation. The danger scale rating provides rudimentary travel advice and a description of the likelihood, overall distribution, and size of expected avalanches. Although it can be used for general avoidance of the hazard, the danger rating alone is not intended to be used for more advanced slope-scale decision making, but rather as a context, or a beginning point for terrain selection decisions and tour planning. The language used in the North American Public Avalanche Danger Scale in regards to avalanche size, likelihood, and distribution, largely corresponds with the Conceptual Model of Avalanche Hazard (CMAH) language to help the forecaster apply the correct rating, and to improve consistency across and between operations.

The Narrative, or “Bottom Line” is a simple, direct, and succinct synopsis of the day’s avalanche hazard. It should focus on the ‘what, where, when, and why’. It is intended to provide a quick overview of the avalanche danger. Avalanche forecasts are used by a wide variety of people with varying skill levels and knowledge. It is important that the narrative is written with common, easily understood language. Industry jargon and slang should be avoided.

Travel advice brings together all of the elements of the forecast to provide the user with simple advice on how to avoid the problem(s) of the day. It is often included in the narrative.

The avalanche problem type is illustrated by an icon or graphic and corresponds to one of the nine avalanche problems.

-Loose Dry -Storm Slab -Persistent Slab -Wet Slab -Cornice

-Loose Wet -Wind Slab -Deep Persistent Slab -Glide

A graphical depiction of the avalanche problem type's location in the terrain by aspect and elevation. Often referred to as a rose, due to its shape, forecasts include a rose for each avalanche problem type present that day.

Often depicted as sliding scale graphics, the likelihood and size are applied to each avalanche problem type present.

The forecast discussion is a deep dive into the current conditions. This is where the forecaster details the observations, information, and data that are driving the forecast and the danger rating. It is intended to inform decision-making for professionals and advanced users. Discussions will often include recent avalanche activity, including aspect, elevation, and location; stability test results; weak layer description, including depth, and date formed and buried; and other relevant information. Most forecasts in the US include a forecast discussion.

Most bulletins include a mountain-specific weather forecast focusing on factors that will influence the hazard or lead to changing conditions.

Avalanche bulletins are most often issued for an entire mountain range or region, covering hundreds, or even thousands, of square miles of mountains, and many different drainages, aspects, slopes, and terrain types. Backcountry forecasts are generally issued for a 24-hour period which may include important changes in weather and avalanche conditions. This presents a variety of challenges for the forecaster.

Forecasters are often faced with a situation where they must extrapolate the danger from a few observations of varying quality across large swaths of terrain. An added challenge is that most of the observations will be clustered around high-use areas, like highway corridors, ski resorts, and popular trailheads. Automated weather station data plays an out-sized role in range-scale forecasting. Being able to effectively interpret this data to estimate snowpack layering, weak layer formation, and avalanche hazard is a critical skill for a backcountry forecaster.

The forecaster must recognize and acknowledge the uncertainty inherent in the process. We focus a lot on slope-scale variability when we make observations and carry out stability tests. In an area as large as a forecast region, the reality is that the danger will vary across the region. The forecast should always err on the side of caution, and apply the highest danger rating expected for the ascribed area, with the option of mentioning that lower danger may be encountered in certain areas and describing them in the narrative.

Weather factors that influence avalanche conditions don’t always correspond neatly with the temporal scale of the avalanche forecast. When changing conditions are expected during the forecast period, the forecast should default to the highest danger rating expected that day, and describe changing conditions in the narrative. Examples include wind events, snowstorms, and daytime heating. These can be some of the most challenging forecasts as they rely heavily on micro-scale weather forecasting, which adds another layer of uncertainty, and can vary widely across the range.