How to Read an Avalanche Forecast
- Henry
- 3 hours ago
- 10 min read
Skiing Unlocked dives into how to read – and understand – an avalanche forecast.
This addendum is critical here; it simply isn’t good enough to glance at a forecast, grab the headline number, and head out on your way. Guides and avalanche professionals are becoming more and more aware that plenty of people are beginning to carry the right gear, spend the money on an avi airbag, but still only glance at the forecast. Even more so, they glance at the forecast, failing to understand it, but then assume that the warnings provided don’t apply to them – for all the reasons set out in “Human Factors” in my piece here.
Avalanche forecasts are a wealth of information and, what's more, can be fantastically accurate. I've covered here before some scenarios here when I’ve put all this into practice, and a common theme throughout these examples is that the avalanche forecast is exactly right every single time.
In one such instance, I debrief my friends’ avalanche, and note that as much as they are a victim of bad luck in that a series of small decisions coalesce into an avalanche, the avalanche occurs at exactly the elevation and aspect, and because of exactly the problem detailed, as the avalanche forecast said it would; ignore them at your peril!
This is the Skiing Unlocked guide to reading an avalanche forecast.
What's Actually in a Bulletin
At first glance, an avalanche bulletin seems complicated; there is a lot of information being displayed here, and it can be easy to switch off from what it is trying to tell you.
However, all avalanche bulletins the world over tell you the same information, day in and day out. Whilst the danger scale may vary between Europe and North America, it still runs from 1 to 5; whilst both regions use a slightly different nomenclature, all refer to, essentially, the same set of problems that can trigger avalanches.
All reports also follow a “pyramid” system, delivering an avalanche forecast with the most important, “macro” level stuff first, then getting more and more granular as you go down the bulletin.
Let’s begin with the three headline pieces of information available to you: the danger rating, avalanche problem, and aspect and elevation impacted.
The Danger Rating Scale
First up is the part you will be familiar with; the danger rating scale. This is the big headline number that often informs a lot of the decisions you make that day. It is made up of a combination of snowpack stability, problem types, and the potential size of avalanches triggered – on the surface very “macro”, but as we’ll see often without an obvious motivation at first glance.
North America and Europe both use a 1-5 danger rating scale, albeit the nomenclature differs slightly. Here’s a breakdown of both.
Symbol | Rating | European | North American |
 | 1 | Low - The snowpack is well bonded and stable in general. Triggering is generally possible only from high additional loads in isolated areas of very steep, extreme terrain. Only small and medium natural avalanches are possible. | Low - Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human- triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain. |
 | 2 | Moderate - The snowpack is only moderately well bonded on some steep slopes; otherwise well bonded in general. Triggering is possible, primarily from high additional loads, particularly on the indicated steep slopes. Very large natural avalanches are unlikely. | Moderate - Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human- triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas. |
 | 3 | Considerable - The snowpack is moderately to poorly bonded on many steep slopes. Triggering is possible, even from low additional loads, particularly on the indicated steep slopes. In certain situations some large, and in isolated cases very large natural avalanches are possible | Considerable - Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human- triggered avalanches likely. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. |
 | 4 | High - The snowpack is poorly bonded on most steep slopes. Triggering is likely, even from low additional loads, on many steep slopes. In some cases, numerous large and often very large natural avalanches can be expected. | High - Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Natural avalanches likely; human- triggered avalanches very likely. Large avalanches in many areas; or very large avalanches in specific areas. |
| 5 | Very High - The snowpack is poorly bonded and largely unstable in general. Numerous very large and often extremely large natural avalanches can be expected, even in moderately steep terrain | Extreme - Avoid all avalanche terrain. Natural and human- triggered avalanches certain. Large to very large avalanches in many areas. |
Important note – the avalanche danger scale is not linear, i.e. Level 3 does not equate to “medium” or “middle” risk. It is designed to be exponential, meaning each step up between ratings is more and more severe than the last.
A good way remember this is to think about Level 3 – Considerable. If I were to tell you there was a “considerable” chance you’d be hit by a bus crossing the road tomorrow, you’d definitely think twice and look both ways before doing so.
Now put that in an avalanche scenario; if I told you there was a considerable chance of you triggering an avalanche when out in the backcountry tomorrow – yeah, you’d pause and take a second to evaluate your route choices.
The danger rating is set for a large area by a regional or national weather provider, such as MeteoFrance, France’s national meteorological office, or the Utah Avalanche Centre – the regional body in charge of avalanche forecasting, mitigation, recovery and education in the US state of Utah. In some cases, such as in France, it can be varied by those on the ground – critically, never reducing the forecast risk – meaning there may be some discrepancy between the regional bulletin and that showing on indicators in resort.
Along with the number and icon, you will also have a single line of qualifying information, for example for Considerable:
“Human triggered avalanches likely, naturally triggered avalanches probable”
Aspect and Elevation Diagrams
Next is understanding where this risk is going to be the highest.
Different avalanche types are more common at different aspects and elevations than others. A persistent weak layer as a result of depth hoar is most common higher, north facing slopes in mid-winter, as these faces don’t get the sunshine and resultant warmth that helps to evaporate moisture in the snow. On the flip side, a south facing slope in spring will be a hot spot, literally, for wet snow avalanches.
Enter, the avalanche rose. This is a simple, 2D diagram that indicates both the main elevations that the avalanche problem and danger rating will impact, and the aspect (the compass direction a slope faces) that is most at risk.
This diagram from the Utah Avalanche Centre is an example of a 3D rose
The rose indicates the following information:
Grey Shading: Across all compass points, below 8,000ft there is no avalanche risk
Green Shading: On West to East facing slopes between 8,000ft and 9,500ft, there is a danger of Level 1 – Low
Yellow Shading: on west to east facing slopes above 9,500ft, and on northwest to northeast facing slopes between 8,000ft and 9,500ft, there is a danger of Level 2 – Moderate
Orange Shading: on northwest to northeast facing slopes above 9,500ft, there is a danger of Level 3 – Considerable
Not all forecasting bodies use such complex designs. In France, for example, a simple black-and-white rose deals with aspect, and a separate diagram handles elevation.
Avalanche Problem Types
There are five main types of avalanche problem, plus an additional two that you rarely seen on a bulletin. Luckily, both North America and Europe use the same system after North America agreed to broadly adopt the European system in the late 2010s, however some nomenclature differences remain.
I won’t go into the specific differences between the various types, which hopefully were covered on your avalanche course, however I will drop them in below with a brief overview to serve as an aide memoir.
Icon | Problem | Overview |
 | New Snow | The avalanche problem is related to current or most recent snowfall. The amount of additional loading by new snow onto the existing snowpack is the crucial factor of the new snow problem. How critical the loading is depends on various factors such as air temperature or characteristics of the old snow surface. |
 | Wind Slab (EU)/Wind-Drifted Snow (NA) | The avalanche situation is related to wind-drifted snow. Snow can be transported by wind with or without a concurrent snowfall. |
 | Persistent Weak Layer | The avalanche problem is related to the presence of one or more persistent weak layers in the old snowpack. These weak layers typically include faceted crystals, depth hoar or surface hoar |
 | Wet Snow | The avalanche problem is related to weakening of the snowpack due to the presence of liquid water. Water infiltrates the snowpack due to snow melt or rain. |
 | Gliding Snow | The entire snowpack is gliding on the ground, typically on smooth ground such as grassy slopes or smooth rock zones. Glide avalanches are typically related to a thick snowpack with no or only few layers. The release of a glide avalanche is difficult to predict, although glide cracks commonly exist prior to release. |
 | Cornice (Optional) | A wave-like formation of soft or hard wind drifted snow, often overhanging. Cornices often break further back than expected, even onto flat ridgelines, and are the cause of many unexpected falls in the mountains. |
 | Normal Caution (NA)/No Distinct Problem (EU) (Optional) | This is not a specific avalanche problem. It is a very inconclusive scenario, without a clear pattern that a user could follow to lower consequences. Any avalanche type is possible. Do not consider the absence of a typical avalanche problem as safe conditions. |
Other Information
From there the avalanche forecast dives into a more granular-level expose on the expect avalanche problems, as well as providing information on the size and likelihood of avalanches that might occur. This is often very dry but well worth a read, for a few reasons.
Quite simply, it provides more detail than just what the images and icons can provide. Aspect and elevation will be expounded here, as well as the ebb and flow of avalanche issues over the course of the day as the sun moves around the mountain and temperatures rise and fall.
More than that however, there are some practical limitations to avalanche bulletins that this in depth overview can overcome.
Avalanche forecasters will only list up to two avalanche problems on the bulletin. In the very rare scenario where a third (or more) avalanche problem is in play, then it is in here that you will find that information.
In a slightly unfortunate twist, France only publishes official avalanche bulletins in French, something that has rankled English-speaking guides in the country for some time now. Note, however, that even in this granular description, much like with the danger scale and problem icons, they continue to use stock phrases and sayings to help get their message across; “fort vent”, for example, means “high winds” and is featured regularly throughout French forecasts.
There are a couple of resources available that are translating these forecasts using AI; the most prominent so far is Avalanche Clarity (avalancheclarity.com). It is not perfect, like all AI products, so double check it with the real thing, but is an excellent resource nonetheless.
How to Actually Use An Avalanche Forecast
The most important thing to take away from this guide is how to, practically, use the information provided to you in the bulletin.
Avalanche forecasts are made available the day before – for example in France where they are published at 4pm the day before they take effect. Often, you will also have a brief overview of where forecasters expect the danger rating to be going over the next couple of days, too, helping to inform you if there will be better opportunities to conquer the route you have been thinking of doing.
Avalanche bulletins are posted in resort, often in or outside tourist information offices and lift pass counters. They are also available online via two incredibly similar URLs:
Avalanches.org is the main aggregator for all European avalanche warning services, and provides a quick click-through service for all national and regional forecasts
Avalanche.org is the main aggregator for all North America avalanche warning services and provides a quick click-through for all national and regional forecasts
An avalanche forecast should form a key part of your route planning the day before you head out, and not something you scan over at breakfast while grabbing a croissant and coffee and scrambling for first lifts.
It will inform every decision you will go on to make, telling you when and where it will be safe to ski, as well as slopes that require mitigation if you do decide to cross them.
Remember, if snow or weather is the question, then terrain is always the answer; if the avalanche forecast warns of issues on this aspect or this elevation, or because of this particular problem, then choosing sensible terrain is the get out for you to avoid this.
However, don’t be surprised if the avalanche forecast seems a bit clinical or unrelatable when reading it in your chalet in the evening; it is only when paring it with real-life, on the ground feedback when out on snow that you can actually begin to distil the raw facts and figures into something useful.
Understanding the aspect and elevation of the mountain face you are on, feeling the snow change under your skis throughout the day and as you move around the mountain, then thinking about whether this is agrees with what the forecast was telling you – spoiler alert, as we will find out, it more than likely will.
Common Mistakes
The biggest mistake with reading an avalanche forecast is simply glancing at the headline numbers and assuming it applies to you. This is even true if, like me, you pay attention to the snow forecast all season long, and can, more or less, predict an avalanche bulletin before it is released. Read it, read it all, and pay attention to the nuances hiding in some of the finer print; you will be shocked at how useful and truthful this is.
A close second is believing the avalanche forecast doesn’t apply to you. This could be for a variety of factors, including more directly related ones such as familiarity with skiing the terrain your skiing in, and less direct ones, such as the “expert halo” of following, unquestioning, a guide or instructor into terrain you know is dangerous.
Finally, it is treating a forecast as a clearcut “go/no go” decision maker for you. Truthfully, in avalanche science, there is no such thing as a clearcut “go/no go” decision. You can very easily find yourself equivocating a “no go” down into something else, and what can be a “go” first thing in the morning when you set off can quickly become a “no go” when you get delayed at lunch, find yourself on a different aspect to what is planned, or the weather didn’t play out as you expected.
Like all elements of avalanche safety, it forms a key tool in a long series of feedback loops and mechanisms that allow you to constantly assess and re-assess your decisions on a macro and micro level.
Final Thoughts
As noted the intention of this chapter is not to tell you how to read an avalanche forecast. Instead, it is to drive home to you the importance of understanding an avalanche forecast, and the usefulness this tool is in your toolbox of safe decision making.
In the next chapter, we will begin to see what it looks like to put all these things into practice; what feedback from a forecast looks like, what not paying attention to an avalanche forecast looks like, and how to begin drilling down into overcoming the known unknowns.
