If you look at avalanche advisories other English-speaking countries like Canada and New Zealand, they will look similar to our advisory. Most elements of this look actually started in Utah and spread to many other parts of the world and evolved in the process. Now, it's our turn to match the look that other countries have gravitated towards. In the summer of 2012, many of the U.S. avalanche centers in our region met to negotiate a common look and although each has a somewhat different style, they all contain the same elements and approach.
First, realize that the avalanche advisory is designed for people who have taken at least an avalanche awareness class or preferably an avalanche Level 1 course. So we don't expect a first time user to understand the contents of an advisory. This is a tutorial to explain the basic concepts of the advisory and how to read it.
The Mountain Graphic
For those who just want a general overview of the avalanche danger, we provide the mountain graphic with just a short paragraph on the "Bottom Line" information. You can find this on our home page by mousing over the region on the map. This section many tell you whether you can safely walk you dog on a mountain trail or snowmobile on a mountain road. By clicking on the region from the map, you see the full advisory, which provides more specific avalanche information you will need for more specific trip planning decisions. For a tutorial on danger ratings click HERE.
There are many different kinds of avalanches and each has its own characteristics--how to recognize, how to manage and how long they will last. Most Level 1 avalanche classes cover these various avalanche problems. For more info, check out our Avalanche Problem Toolbox.
For each problem, we tell you both graphically and in text, where you will find the problem by aspect and elevation, the characteristics of the problem such as how easy it is to trigger, size, distribution the expected future trend and how to manage.
The Danger Rose
The danger rose is a powerful way to understand the general avalanche pattern in a glance by aspect (the direction a slope faces) and elevation.
Imagine looking straight down on a mountain from above where the center of the diagram is the top of the mountain and the outside edges of the diagram are the lowest elevation terrain. We provide a 3-d rose to help visualize this. The shape of the diagram is supposed to remind you that mountains have many ridges, gullies and bowls. For instance, even on the south side of a mountain, the sides of gullies or ridges may face east or west and there may be parts of a bowl that actually face north. Aspect is aspect no matter where you find it.
Likelihood of Triggering means the probability that a single person will trigger that type of avalanche in the terrain in the highest danger rating for that problem. On the danger scale, the spectrum goes from "Unlikely" to "Certain".
Size means the size of the expected avalanche. Small avalanches are generally "Class 1" avalanches, which generally will not bury a person unless you are in high consequence terrain such as a terrain trap. The large avalanches are "Class 5" avalanches, which are extremely large, destructive, and most likely unsurvivable.
Trend means the expected future trend of the avalanche danger, getting safer, staying the same or getting more dangerous.
Finally, remember this information is only for AVALANCHE TERRAIN, which is generally slopes steeper than 30 degrees (or flatter slopes locally connected to steeper terrain). Even on high danger days you can find much safer terrain if you stay on slopes less steep than about 30 degrees that are not underneath steeper terrain. The danger ratings are generally calibrated for terrain between 34 and 45 degrees where 3 out of 4 human triggered avalanches occur.