The assessment of avalanche risk is of utmost importance in winter for all-mountain sports – be it ski mountaineering, winter hiking, ice climbing. Decision-makers here are based on individual factors (knowledge, experience, ambitions, psyche, group influence, etc.) and topographical conditions (steepness, exposure, altitude) as well as local weather and snow conditions. For the latter, an avalanche situation report (avalanche forecast, avalanche bulletin) is the most important source one can tap into. This article explains what information the avalanche warning services provide, how you can use it for your route planning, and where there are still differences between the various services on offer.
Avalanche reports in the Alps
Along the entire Alpine arc, between the Maritime Alps in the west and the Schneeberg just before Vienna in the east, a total of 17 different national or regional warning services publish information on the local avalanche situation. Under the umbrella of EAWS (European Avalanche Warnings Services), all kinds of common standards have been agreed upon over the past 35 years, ranging from a uniform hazard scale to so-called avalanche problems. On the EAWS website, you can click on an interactive map to access the respective websites and often also directly to the situation reports of the membership organizations.
The information pyramid: First things first
Ideally, an avalanche situation report is structured on the basis of the information pyramid above. The presentation follows the two principles of “first things first” and “from easy to difficult”. This means that at the top and most conspicuously displayed is the danger level at which all available information has been reduced to one number. This is followed by information on altitude and exposure as well as the basic avalanche risk. This is followed by more detailed information on the hazard assessment and additional information on the snowpack structure and weather forecast. Further background information such as accident analyses, station readings, or snow profiles ought to further complement the information collected.
Avalanche forecast and individual slope evaluation
The information in the avalanche bulletins always applies to a larger area (> 100 square kilometres). The danger level provides information on the distribution of the danger zones, the probability of triggering, and the size of the avalanche in the entire focus region. It is therefore a kind of mean value, which can have more or fewer outliers depending on the situation. Thus, even at level 1 (low avalanche danger), there may be dangerous spots, just as at level 5 there may still be a stable slope somewhere. The danger level cannot, therefore, provide any concrete information about the stability of the snowpack on any single slope. It is always only an indication of the probability of the individual slope being considered safe or critical. With the information in the lower levels of the information pyramid, you can further substantiate this statement’s probability. The avalanche situation report is therefore primarily a tool for route planning. A differentiated assessment usually requires further observations when on the go (e.g. whether fresh drift snow is present on the slope).
Danger level
The avalanche danger is divided into five levels from level 1 (low) to level 5 (very high). The latter is extremely rare (on average less than one day per winter, in many years not at all), so only levels 1-4 are actually relevant for ski tourers. While even beginners can go on the usual, regularly used standard tours if the avalanche danger is low, level 4 (high) means that even the professionals have to think carefully about which tours are still justifiable. Level 2 and Level 3 are particularly interesting, as they offer the widest range of options. To do this, you move down the information pyramid and look in more detail at which altitudes and which slope directions are primarily affected and what kind of avalanche problem you are actually dealing with.
Avalanche problems
By means of characteristic symbols or in the text, one or more of the following five avalanche problems are usually mentioned, to which special attention should/must be paid:
- Fresh/New snow
If a lot of snowfalls in a short period of time, even the layman can see that the danger of avalanches increases. What “a lot” means depends on how favourable the surface of the old snow is for bonding with it and how evenly and at what temperatures the snowfalls. In addition, the catchment area must be taken into account, as spontaneous avalanches often occur there. Often of particular note: the first beautiful day after a new snowfall. - Wind-Drift snow
In most cases, this is also of importance when a fresh dump is concerned. Snow carried by the wind always binds itself to a snow slab and is often more than easy to trigger, especially in colder temperatures. Tricky: a slab can suddenly pop many days after the last snowfall, even in bright sunshine, as soon as the wind picks up and carries snow from A to B. Advantage: Dangerous places are usually easy for experienced people to recognise and deal with in good visibility. - Persistent weak layers
The most insidious situation in which a weak layer in the old snow cover (e.g. floating snow) can break on a stress impulse and the break in the snow cover can spread over a very large area. Problem: Difficult to detect or assess even by professionals. Recommendation: Avoid the areas mentioned in the report completely or only walk over them with a large distance between skiers. - Wet snow
Warming or rain drenches the snowpack down to a weak layer and reduces the stability of the snowpack so that it can slide off (usually as a spontaneous avalanche). Advantage: After clear nights super stable snow cover and then with the right timing very safe to handle. Critical: Unexpected cloudy night and especially incipient rain. - Snow Slabs and Gliding snow
The entire snow cover glides off spontaneously from the surface. Such avalanches cannot be triggered by additional loads on skiers, nor can their trigger time be predicted accurately. Suh snow slabs are similar to wet snow avalanches and tend to slide off in very humid conditions (rain, thaw from midday onwards until shortly after sunset). Dry sliding snow avalanches, on the other hand, can also be set off at night and in very cold weather – the avalanche situation report provides information on the risk of this. Please note: Avoid areas under sliding snow cracks (fish mouths) or cross them quickly if needs be.
Risk assessment and additional information
These text sections of the Bulletins normally provide a more detailed breakdown of the information from the preceding, highly summarised, or only graphically displayed levels of the information pyramid. They may contain detailed information on the types of terrain affected, the size of the avalanches possible, the probability of triggering (spontaneous avalanches or those that can be triggered with low or high additional loads), or local specifics. Furthermore, critical weak layers, amounts of new snow, or the condition of the snow surface (broken snow or powder snow) may be mentioned. Relevant information on weather conditions (expected new snow, temperature profile, wind) is also included.
More
Almost every avalanche warning service also offers other useful services which, although are not a must, but can still provide welcome input for those interested. For example, the Bavarian Avalanche Warning Service and the SLF from Switzerland provide weekly reports before every weekend, which provide a review of the past days, new snowfall, the snowpack, the recent avalanche activity, and often also on ski touring conditions (snow line, snow quality). A similar service is provided by the Avalanche Warning Service Tyrol in its blog, where concrete information on upcoming special avalanche situations or analyses of accidents can also be found if required. Tour forums in which users post pictures and tour conditions are very popular with the warning services in eastern Austria (Salzburg, Styria).
Differences between the individual avalanche reports
Despite many standardizations, differences in the presentation and usability of the various avalanche situation reports are noticeable from a first glance. Switzerland, a multilingual country, offers information in four languages (German, English, French, Italian). The joint Euregio project for Tyrol, South Tyrol, and Trentino has three languages on offer (DE, IT, EN). Otherwise, an English version is often available in addition to the national language or there is an automated Google translation available. Some Austrian, Italian, French, and Slovenian situation reports are only available in the national language.
The avalanche forecasts for Bavaria, Switzerland, France, and Slovenia are uniform throughout the country and are structured in a somewhat similar way by all warning services using the information pyramid. However, this system has not yet transgressed to France. Forecasts are prepared the evening before for the next day, with the release dates differing slightly (4 p.m. – 5.30 p.m.). If necessary, an update is made in the morning. The exception is Slovenia, where the report is published in the morning.
In Austria, each federal state has its own avalanche warning service and maintains a specific website. Usually, the bulletins are published the evening before, in Vorarlberg only in the morning. Most of the time, the structure follows the above standard scheme – only in Salzburg no avalanche report is made accessible. A special case is Tyrol. Since last winter a joint situation report has been published for the EUREGIO Tyrol, South Tyrol, and Trentino.
This brings us to Italy, where the most chaotic picture is to be found. This begins with the fact that various institutions are involved in avalanche warnings. Across Italy, the Ministry of Defence or its department Meteomont competes with the actual avalanche warning service AINEVA. It can happen that different warning levels are issued for the same area. AINEVA is more detailed and differentiated, but only in Italian. The autonomous provinces of Aosta, South Tyrol, and Trentino have their own departments for avalanche warnings. However, the latter two publish their avalanche report together with Tyrol in the EUREGIO report. AINEVA also has these regions in its portfolio and publishes its own situation report every few days (which does not necessarily coincide with the other one).
IFALP
In addition to the merger of the avalanche warning services in the EAWS, an initiative on the part of users was founded in winter 2019/20, which is also working towards the standardisation of the various situation reports across the Alps. In addition to the deviations in accessibility and usability listed above, the standards actually set, such as the definitions of the avalanche danger level, are also interpreted differently. One study found that, for example, the French situation report or AINEVA issued hazard levels 4 and 5 significantly more frequently than in Austria or Switzerland. More detailed information can be found on the Ifalp.org website.