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Avalanche bulletin through Friday, 30 September 2022
Striking onset of winter, snowfall down to below 2000 m
Edition: Mo. 26.09., 17:00 Next update: In the event of heavy snowfall Validity
Avalanche bulletin through Friday, 30 September 2022
Striking onset of winter, snowfall down to below 2000 m
Edition Mo. 26.09., 17:00 Next update In the event of heavy snowfall Validity
Avalanche bulletin through Friday, 30 September 2022
Striking onset of winter, snowfall down to below 2000 m
Edition Mo. 26.09., 17:00 Next update In the event of heavy snowfall Validity
Avalanche bulletin through Friday, 30 September 2022
Striking onset of winter, snowfall down to below 2000 m
Edition Mo. 26.09., 17:00 Next update In the event of heavy snowfall Validity
Striking onset of winter, snowfall down to below 2000 m
Edition: 26.9.2022, 17:00 / Next update: In the event of heavy snowfall
Avalanche danger
Lower Valais, northern Alpine Ridge
Avalanche danger will increase over the next few days.
Above approximately 2500 m, considerable danger of dry-snow slab avalanches can be assumed to prevail starting on Wednesday. The avalanche prone locations are found particularly on wind-loaded slopes and especially wherever there was old snow already on the ground. One single person can trigger an avalanche, and to an increasing extent even medium-sized and large-sized avalanches. Starting on Wednesday, naturally triggered avalanches will also be possible. From high-altitude avalanche starting zones, these can in isolated cases grow to large size and in the typical avalanche plummet paths even penetrate as far down as intermediate altitude zones. On mountain tours, experience and caution are indispensable.
Below approximately 2500 m, the major danger stems from wet-snow and glide-snow avalanches. The avalanche prone locations are found particularly on smooth grassy meadows and rock plates in all aspects. Avalanches can expand to medium size, sweep persons along in their path and force them to take a fall. In the case of hikers, bikers and hunters, a high degree of caution is urged especially in exposed terrain. High-altitude, exposed transportation routes can in isolated cases be put at risk by hillside snowslides.
Above approximately 2500 m, considerable danger of dry-snow slab avalanches can be assumed to prevail starting on Wednesday. The avalanche prone locations are found particularly on wind-loaded slopes and especially wherever there was old snow already on the ground. One single person can trigger an avalanche, and to an increasing extent even medium-sized and large-sized avalanches. Starting on Wednesday, naturally triggered avalanches will also be possible. From high-altitude avalanche starting zones, these can in isolated cases grow to large size and in the typical avalanche plummet paths even penetrate as far down as intermediate altitude zones. On mountain tours, experience and caution are indispensable.
Below approximately 2500 m, the major danger stems from wet-snow and glide-snow avalanches. The avalanche prone locations are found particularly on smooth grassy meadows and rock plates in all aspects. Avalanches can expand to medium size, sweep persons along in their path and force them to take a fall. In the case of hikers, bikers and hunters, a high degree of caution is urged especially in exposed terrain. High-altitude, exposed transportation routes can in isolated cases be put at risk by hillside snowslides.
Remaining regions not including southern flank of the Alps
Above approximately 2500 m, the major danger stems from dry-snow slab avalanches. Avalanches can be triggered even by one
single person. These releases tend to be predominantly small sized, but can sweep persons along in their path and force them
to take a fall. Caution is urged on wind-loaded slopes above all else.
Below approximately 2500 m, mostly small-sized glide-snow or wet-snow slides are possible. Caution is urged in exposed terrain in particular.
Below approximately 2500 m, mostly small-sized glide-snow or wet-snow slides are possible. Caution is urged in exposed terrain in particular.
Southern flank of the Alps
Isolated avalanche prone locations are found in high alpine regions in extremely steep terrain.
Snow and weather
Snowpack
At intermediate and high altitudes, the fresh fallen snow over widespread areas was deposited on bare ground. In high alpine
regions and there in particular in glaciated terrain, prior to this bout of snowfall there was already a shallow, cohesive,
area-wide snowpack from the precipitation in August and September. In addition, the prognosticated snowfall fell in a series
of rounds, with a number of interims in the precipitation. For that reason, at high altitudes a snowpack is likely to develop
which to an increasing degree will comprise a variety of layers.
Weather review to Saturday, 24 September
Since Saturday there has been intermittent precipitation registered. The snowfall level descended from 2500 m down to just
below 2000 m. In northern Grisons and in the Lower Engadine, there was 10 to 25 cm of fresh snow registered, in the remaining
regions only a few centimetres of fresh snow.
Weather outlook through Friday, 30 September
From Monday through Friday, batches of moist air will be accumulated and dammed up against the northern flank of the Alps,
arriving in several bouts of precipitation. The precipitation will frequently be intensive, particularly on Wednesday in the
western and in the northern regions. The snowfall level is expected to descend on Tuesday down to 1400 to 1700 m, subsequently
ascend on Wednesday in the western regions to nearly 2400 m temporarily, in the eastern regions to nearly 2000 m temporarily.
On Thursday and on Friday, the snowfall level will lie at approximataely 1600 m in the northern regions and at 2000 m in the
southern regions. By Friday evening, the following amounts of fresh fallen snow are anticipated above approximtely 2500 m:
-
Furthermost western part of Lower Valais, northern Alpine Ridge from Les Diablerets into the Bernese Alps: 60 to 80 cm;
- remaining parts of Lower Valais, northern Alpine Ridge from the Bernese Alps into Liechtenstein: 40 to 60 cm;
- remaining regions of Switzerland: 20 to 40 cm, on the southern flank of the Alps only a few centimetres or it will remain dry.
Outlook
Next weekend, further rounds of precipitation are expected. Depending on the amount of actual precipitation, the avalanche
danger levels can be expected to increase anew. If necessary, a separate Avalanche Bulletin will be published to describe
and explain the situation.
Keep informed about the publication of unannounced Avalanche Bulletins. Activate in the App WhiteRisk the "Push Summer Bulletin".
Striking onset of winter, snowfall down to below 2000 m
Edition: 26.9.2022, 17:00 / Next update: In the event of heavy snowfall
Avalanche danger
Lower Valais, northern Alpine Ridge
Avalanche danger will increase over the next few days.
Above approximately 2500 m, considerable danger of dry-snow slab avalanches can be assumed to prevail starting on Wednesday. The avalanche prone locations are found particularly on wind-loaded slopes and especially wherever there was old snow already on the ground. One single person can trigger an avalanche, and to an increasing extent even medium-sized and large-sized avalanches. Starting on Wednesday, naturally triggered avalanches will also be possible. From high-altitude avalanche starting zones, these can in isolated cases grow to large size and in the typical avalanche plummet paths even penetrate as far down as intermediate altitude zones. On mountain tours, experience and caution are indispensable.
Below approximately 2500 m, the major danger stems from wet-snow and glide-snow avalanches. The avalanche prone locations are found particularly on smooth grassy meadows and rock plates in all aspects. Avalanches can expand to medium size, sweep persons along in their path and force them to take a fall. In the case of hikers, bikers and hunters, a high degree of caution is urged especially in exposed terrain. High-altitude, exposed transportation routes can in isolated cases be put at risk by hillside snowslides.
Above approximately 2500 m, considerable danger of dry-snow slab avalanches can be assumed to prevail starting on Wednesday. The avalanche prone locations are found particularly on wind-loaded slopes and especially wherever there was old snow already on the ground. One single person can trigger an avalanche, and to an increasing extent even medium-sized and large-sized avalanches. Starting on Wednesday, naturally triggered avalanches will also be possible. From high-altitude avalanche starting zones, these can in isolated cases grow to large size and in the typical avalanche plummet paths even penetrate as far down as intermediate altitude zones. On mountain tours, experience and caution are indispensable.
Below approximately 2500 m, the major danger stems from wet-snow and glide-snow avalanches. The avalanche prone locations are found particularly on smooth grassy meadows and rock plates in all aspects. Avalanches can expand to medium size, sweep persons along in their path and force them to take a fall. In the case of hikers, bikers and hunters, a high degree of caution is urged especially in exposed terrain. High-altitude, exposed transportation routes can in isolated cases be put at risk by hillside snowslides.
Remaining regions not including southern flank of the Alps
Above approximately 2500 m, the major danger stems from dry-snow slab avalanches. Avalanches can be triggered even by one
single person. These releases tend to be predominantly small sized, but can sweep persons along in their path and force them
to take a fall. Caution is urged on wind-loaded slopes above all else.
Below approximately 2500 m, mostly small-sized glide-snow or wet-snow slides are possible. Caution is urged in exposed terrain in particular.
Below approximately 2500 m, mostly small-sized glide-snow or wet-snow slides are possible. Caution is urged in exposed terrain in particular.
Southern flank of the Alps
Isolated avalanche prone locations are found in high alpine regions in extremely steep terrain.
Snow and weather
Snowpack
At intermediate and high altitudes, the fresh fallen snow over widespread areas was deposited on bare ground. In high alpine
regions and there in particular in glaciated terrain, prior to this bout of snowfall there was already a shallow, cohesive,
area-wide snowpack from the precipitation in August and September. In addition, the prognosticated snowfall fell in a series
of rounds, with a number of interims in the precipitation. For that reason, at high altitudes a snowpack is likely to develop
which to an increasing degree will comprise a variety of layers.
Weather review to Saturday, 24 September
Since Saturday there has been intermittent precipitation registered. The snowfall level descended from 2500 m down to just
below 2000 m. In northern Grisons and in the Lower Engadine, there was 10 to 25 cm of fresh snow registered, in the remaining
regions only a few centimetres of fresh snow.
Weather outlook through Friday, 30 September
From Monday through Friday, batches of moist air will be accumulated and dammed up against the northern flank of the Alps,
arriving in several bouts of precipitation. The precipitation will frequently be intensive, particularly on Wednesday in the
western and in the northern regions. The snowfall level is expected to descend on Tuesday down to 1400 to 1700 m, subsequently
ascend on Wednesday in the western regions to nearly 2400 m temporarily, in the eastern regions to nearly 2000 m temporarily.
On Thursday and on Friday, the snowfall level will lie at approximataely 1600 m in the northern regions and at 2000 m in the
southern regions. By Friday evening, the following amounts of fresh fallen snow are anticipated above approximtely 2500 m:
-
Furthermost western part of Lower Valais, northern Alpine Ridge from Les Diablerets into the Bernese Alps: 60 to 80 cm;
- remaining parts of Lower Valais, northern Alpine Ridge from the Bernese Alps into Liechtenstein: 40 to 60 cm;
- remaining regions of Switzerland: 20 to 40 cm, on the southern flank of the Alps only a few centimetres or it will remain dry.
Outlook
Next weekend, further rounds of precipitation are expected. Depending on the amount of actual precipitation, the avalanche
danger levels can be expected to increase anew. If necessary, a separate Avalanche Bulletin will be published to describe
and explain the situation.
Keep informed about the publication of unannounced Avalanche Bulletins. Activate in the App WhiteRisk the "Push Summer Bulletin".
Your observations can improve the quality of the avalanche bulletin. We are very grateful for any reports and photos received.
Please report your observations of avalanches or alarm signs, or your estimation of the avalanche danger, or simply send us a picture illustrating the current situation. Your report from the field will be considered along with all the other information when we assess the avalanche danger. It is impossible, however, to reflect the exact content of each individual report in the avalanche bulletin.
The best way to file a report is by completing the interactive form on this page. If your report is to be used in the 5 pm avalanche bulletin, it should be submitted before 2:30 pm if possible. Reports received later will normally be given consideration in the next assessment.
Other reporting options:
- White Risk App
- E-mail to bulletin(at)slf.ch
- Freephone number 0800 800 187
Striking onset of winter, snowfall down to below 2000 m
Edition: 26.9.2022, 17:00 / Next update: In the event of heavy snowfall
Avalanche danger
Lower Valais, northern Alpine Ridge
Avalanche danger will increase over the next few days.
Above approximately 2500 m, considerable danger of dry-snow slab avalanches can be assumed to prevail starting on Wednesday. The avalanche prone locations are found particularly on wind-loaded slopes and especially wherever there was old snow already on the ground. One single person can trigger an avalanche, and to an increasing extent even medium-sized and large-sized avalanches. Starting on Wednesday, naturally triggered avalanches will also be possible. From high-altitude avalanche starting zones, these can in isolated cases grow to large size and in the typical avalanche plummet paths even penetrate as far down as intermediate altitude zones. On mountain tours, experience and caution are indispensable.
Below approximately 2500 m, the major danger stems from wet-snow and glide-snow avalanches. The avalanche prone locations are found particularly on smooth grassy meadows and rock plates in all aspects. Avalanches can expand to medium size, sweep persons along in their path and force them to take a fall. In the case of hikers, bikers and hunters, a high degree of caution is urged especially in exposed terrain. High-altitude, exposed transportation routes can in isolated cases be put at risk by hillside snowslides.
Above approximately 2500 m, considerable danger of dry-snow slab avalanches can be assumed to prevail starting on Wednesday. The avalanche prone locations are found particularly on wind-loaded slopes and especially wherever there was old snow already on the ground. One single person can trigger an avalanche, and to an increasing extent even medium-sized and large-sized avalanches. Starting on Wednesday, naturally triggered avalanches will also be possible. From high-altitude avalanche starting zones, these can in isolated cases grow to large size and in the typical avalanche plummet paths even penetrate as far down as intermediate altitude zones. On mountain tours, experience and caution are indispensable.
Below approximately 2500 m, the major danger stems from wet-snow and glide-snow avalanches. The avalanche prone locations are found particularly on smooth grassy meadows and rock plates in all aspects. Avalanches can expand to medium size, sweep persons along in their path and force them to take a fall. In the case of hikers, bikers and hunters, a high degree of caution is urged especially in exposed terrain. High-altitude, exposed transportation routes can in isolated cases be put at risk by hillside snowslides.
Remaining regions not including southern flank of the Alps
Above approximately 2500 m, the major danger stems from dry-snow slab avalanches. Avalanches can be triggered even by one
single person. These releases tend to be predominantly small sized, but can sweep persons along in their path and force them
to take a fall. Caution is urged on wind-loaded slopes above all else.
Below approximately 2500 m, mostly small-sized glide-snow or wet-snow slides are possible. Caution is urged in exposed terrain in particular.
Below approximately 2500 m, mostly small-sized glide-snow or wet-snow slides are possible. Caution is urged in exposed terrain in particular.
Southern flank of the Alps
Isolated avalanche prone locations are found in high alpine regions in extremely steep terrain.
Snow and weather
Snowpack
At intermediate and high altitudes, the fresh fallen snow over widespread areas was deposited on bare ground. In high alpine
regions and there in particular in glaciated terrain, prior to this bout of snowfall there was already a shallow, cohesive,
area-wide snowpack from the precipitation in August and September. In addition, the prognosticated snowfall fell in a series
of rounds, with a number of interims in the precipitation. For that reason, at high altitudes a snowpack is likely to develop
which to an increasing degree will comprise a variety of layers.
Weather review to Saturday, 24 September
Since Saturday there has been intermittent precipitation registered. The snowfall level descended from 2500 m down to just
below 2000 m. In northern Grisons and in the Lower Engadine, there was 10 to 25 cm of fresh snow registered, in the remaining
regions only a few centimetres of fresh snow.
Weather outlook through Friday, 30 September
From Monday through Friday, batches of moist air will be accumulated and dammed up against the northern flank of the Alps,
arriving in several bouts of precipitation. The precipitation will frequently be intensive, particularly on Wednesday in the
western and in the northern regions. The snowfall level is expected to descend on Tuesday down to 1400 to 1700 m, subsequently
ascend on Wednesday in the western regions to nearly 2400 m temporarily, in the eastern regions to nearly 2000 m temporarily.
On Thursday and on Friday, the snowfall level will lie at approximataely 1600 m in the northern regions and at 2000 m in the
southern regions. By Friday evening, the following amounts of fresh fallen snow are anticipated above approximtely 2500 m:
-
Furthermost western part of Lower Valais, northern Alpine Ridge from Les Diablerets into the Bernese Alps: 60 to 80 cm;
- remaining parts of Lower Valais, northern Alpine Ridge from the Bernese Alps into Liechtenstein: 40 to 60 cm;
- remaining regions of Switzerland: 20 to 40 cm, on the southern flank of the Alps only a few centimetres or it will remain dry.
Outlook
Next weekend, further rounds of precipitation are expected. Depending on the amount of actual precipitation, the avalanche
danger levels can be expected to increase anew. If necessary, a separate Avalanche Bulletin will be published to describe
and explain the situation.
Keep informed about the publication of unannounced Avalanche Bulletins. Activate in the App WhiteRisk the "Push Summer Bulletin".
Have you observed alarm signs or an avalanche?
Your observations can improve the quality of the avalanche bulletin. We are very grateful for any reports and photos received.
More information about observations
Please report your observations of avalanches or alarm signs, or your estimation of the avalanche danger, or simply send us a picture illustrating the current situation. Your report from the field will be considered along with all the other information when we assess the avalanche danger. It is impossible, however, to reflect the exact content of each individual report in the avalanche bulletin.
The best way to file a report is by completing the interactive form on this page. If your report is to be used in the 5 pm avalanche bulletin, it should be submitted before 2:30 pm if possible. Reports received later will normally be given consideration in the next assessment.
Other reporting options:
- White Risk App
- E-mail to bulletin(at)slf.ch
- Freephone number 0800 800 187
No avalanche bulletin is published currently. Nevertheless, you should still stay up to date with the avalanche situation in the mountains, especially if there is fresh snow.
However, the SLF will, by way of exception, also issue avalanche bulletins in the summer in case of heavy snowfall. There are different ways you can be notified when these bulletins based on the snow situation are published:
- by push alert on SLF's free White Risk mobile app: appearing in four languages (English, German, French and Italian), this can be downloaded from iTunes App Store (for iPhones) or Google Play Store (for Android);
- via an RSS feed which informs you whenever an avalanche bulletin is published.
Depending on the snow and avalanche situation, the regular publication of avalanche bulletins recommences in November/December.
Have you observed alarm signs or an avalanche?
Your observations can improve the quality of the avalanche bulletin. We are very grateful for any reports and photos received.
More information about observations
Please report your observations of avalanches or alarm signs, or your estimation of the avalanche danger, or simply send us a picture illustrating the current situation. Your report from the field will be considered along with all the other information when we assess the avalanche danger. It is impossible, however, to reflect the exact content of each individual report in the avalanche bulletin.
The best way to file a report is by completing the interactive form on this page. If your report is to be used in the 5 pm avalanche bulletin, it should be submitted before 2:30 pm if possible. Reports received later will normally be given consideration in the next assessment.
Other reporting options:
- White Risk App
- E-mail to bulletin(at)slf.ch
- Freephone number 0800 800 187
Danger levels
The SLF uses the five-level European avalanche danger scale to denote the avalanche danger. The danger level depends on a range of variables, in particular the snowpack stability, i.e. the probability of an avalanche triggering; the prevalence of avalanche prone locations; and potential avalanche size. The probability of an avalanche triggering increases sharply as the danger level rises.
A danger level always applies to one region and cannot reflect the peculiarities of a specific individual slope. In addition, the danger level stated in the Avalanche Bulletin is always a prediction and should be evaluated on-site.
Avalanche danger scale
Short version
Danger level | Characteristics | Recommendations for backcountry recreationists |
5 very high | Extraordinary avalanche situation Numerous very large and extremely large natural avalanches can be expected. These can reach roads and settlements in the valley. | You are advised not to engage in winter sports beyond open ski runs and trails. Very rarely forecast. Around 1 % of avalanche fatalities. |
4 high | Very critical avalanche situation Natural and often very large avalanches are likely. Avalanches can easily be triggered on many steep slopes. Remote triggering is typical. Whumpf sounds and shooting cracks occur frequently. | Stay on moderately steep terrain. Heed runout zones of large avalanches. Unexperienced persons should remain on open ski runs and trails. Forecast only on a few days throughout the winter. Around 10 % of avalanche fatalities. |
3 considerable | Critical avalanche situation Whumpf sounds and shooting cracks are typical. Avalanches can easily be triggered, particularly on steep slopes with the aspect and elevation indicated in the avalanche bulletin. Natural avalanches and remote triggering can occur. | The most critical situation for backcountry recreationists. Select best possible route and take action to reduce risks. Avoid very steep slopes with the aspect and elevation indicated in the avalanche bulletin. Unexperienced persons are advised to remain on open ski runs and trails. Forecast for around 30 % of the winter season. Around 50 % of avalanche fatalities. |
2 moderate | Mostly favourable avalanche situation Warning signs can occur in isolated cases. Avalanches can be triggered in particular on very steep slopes with the aspect and elevation indicated in the avalanche bulletin. Relatively large natural avalanches are not to be expected. | Routes should be selected carefully, especially on slopes with the aspect and elevation indicated in the avalanche bulletin. Travel very steep slopes one person at a time. Pay attention to unfavourable snowpack structure (persistent weak layers, old snow problem). Forecast for around 50 % of the winter season. Around 30 % of avalanche fatalities. |
1 low | Generally favourable avalanche situation No warning signs present. Avalanches can only be triggered in isolated cases, in particular on extremely steep slopes. | Travel extremely steep slopes one person at a time and be alert to the danger of falling. Forecast for around 20 % of the winter season. Around 5 % of avalanche fatalities. |
Full description of the European avalanche danger scale
This scale, introduced by the European Avalanche Warning Services on winter 1993/94, defines the danger level based on the snowpack stability and the avalanche triggering probability. The full description of the scale also includes other columns that have not been internationally agreed relating to typical characteristics, recommendations and consequences.
European Danger Scale with recommendations and additions (.pdf)
Danger levels – a simplified picture of reality
The avalanche danger does not increase in linear fashion from one level to another, but disproportionately. As the danger level increases,
- snowpack stability, and therefore the additional load required to trigger an avalanche, decreases. In consequence, the probability of an avalanche triggering increases.
- the prevalence of avalanche prone locations increases. In other words, there are more places where avalanches can release naturally or be triggered.
- avalanche size increases as well, in particular when the danger level is at the higher end of the scale.
If the additional load required to trigger an avalanche decreases and there are also more locations where avalanches can be triggered, the avalanche triggering probability increases. This is also shown by the stability distribution in the chart below.
In a typical case, all these influencing variables change as indicated above. This means that in the case of 'low' avalanche danger, usually only small avalanches are triggered in just a few locations and mostly only due to a high additional load, while in the case of 'high' avalanche danger, a lot of avalanches, some of them very large, are triggered or are released naturally (without human influence).
However, there are also atypical situations that do not fit into this picture. These are detailed in the next section.
Various characteristics of avalanche danger
Also in the case of less typical avalanche situations the danger level is a measure of the order of magnitude of the avalanche danger. These situations are detailed below along with information about their assessment by the avalanche warning service. As these are atypical situations, no list can ever be exhaustive. In atypical situations deviations from the danger level definition are inevitable. These are set out as far as possible in the avalanche bulletin's danger description.
Faceted-crystal snowpack
In the case of low avalanche danger (level 1) the snowpack is normally well bonded and stable. However, after long periods of fine weather with shallow snow, another form of snow occurring in mid-winter which makes slab avalanches virtually impossible is the whole snowpack being loose and transformed into faceted crystals. The snowpack is then very weak and there are also weak layers, but the bonded layer on top (the 'slab') is lacking. With no bonded layer a fracture cannot be propagated, meaning that there is no possibility of a slab avalanche forming. This means there is a low avalanche danger (level 1), despite or precisely because of the very loose snowpack. 'Stable snowpack' means 'not liable to trigger slab avalanches' and does not refer to the hardness of the layers.
This situation is not a good omen for the immediate future, given that as soon as it is snowed on, the fresh-fallen snow and fresh snowdrift result in the creation of a 'slab' where one did not exist before. Underneath this is the loose old snowpack in the form of a substantial weak layer. The avalanche danger will increase significantly, generally resulting in a long-lasting old-snow problem.
Small, easily triggered snowdrift accumulations
Fresh snowdrift accumulations can often be triggered by individual winter sports enthusiasts. The size of the snowdrift accumulations depends not only on the wind but also on the supply of fresh and old snow which can be transported. For only little snow which can be transported, the snowdrift accumulations are usually so small that getting buried by them is unlikely. In this case, level 2 (moderate) is often used despite the high probability of an avalanche release. In such situations the snowdrift accumulations can usually be seen in good visibility by the trained eye. They need to be avoided especially on terrain where there is a danger of falling.
Old-snow problem with a significant weak layer deep down in the snowpack
The more thickly a weak layer is covered, the more difficult it becomes for a fracture to form there. This is most likely to occur in locations where the snow is relatively shallow or in transitions from shallow to deep snow. In the case of an old-snow problem with a significant weak layer deep down in the snowpack, avalanche prone locations are usually relatively rare. However, avalanches often reach large size, and are therefore particularly dangerous for winter sports enthusiasts. Therefore, the avalanche danger in the case of an old snow problem can sometimes be considerable (level 3) even if the avalanche prone locations are fairly rare. An aggravating factor is that the avalanche prone locations are barely recognisable in old snow situations, even to the trained eye. In the case of weak old snow, more fatalities can be expected than in the case of the other avalanche problems (at the same danger level).
'Skier high'
If numerous large and, in many cases, very large natural avalanches can be expected, the avalanche danger is classified as 'high’ (level 4). In these circumstances, exposed objects (mostly sections of transportation routes, but also buildings in isolated cases) can be endangered. Parallel to this classic 'road high' situation there is a further variant of this danger level when, even though very large avalanches are unlikely to occur, there are a lot of places where people can very easily trigger medium and large-sized avalanches. In many such cases, avalanches are released naturally as well. In the case of this 'skier high', winter sports enthusiasts are in severe danger away from secured ski runs. Transportation routes, in contrast, are either unaffected or affected only in isolated cases.
Avalanche activity in case of wet and gliding snow
Wet-snow avalanches are seldom triggered by people, and in the case of gliding avalanches this is virtually impossible. Therefore, natural triggering is the main cause of such avalanche types even in the when lower danger levels prevail. The maximum possible naturally triggered avalanche activity, based on the defined danger level, relates mainly to wet-snow and gliding-snow conditions and less to conditions involving dry avalanches. In this context large natural avalanches are possible when there is a moderate danger of wet-snow or gliding avalanches. In the case of a situation with dry-snow avalanches, such naturally triggered avalanche activity normally corresponds to a considerable avalanche danger, as then avalanches are also expected to be triggered by individuals.
Change in the avalanche danger as the day progresses
The avalanche danger changes over time and may not reach or overshoot the boundary between one danger level and another within the period of validity of the avalanche bulletin. Ordinarily the danger increases, for example because snowfall or wind, significantly faster than it recedes again.
If the danger level is likely to change during the day, the level published in the avalanche bulletin and the danger description normally show the situation in the morning. The change (often an increase) is indicated in the danger description. Here are some examples:
- "The avalanche danger will increase and reach level 3 (considerable) in the afternoon." In this case, level 2 (moderate) is marked on the hazard map.
- "Danger level 4 (high) will be reached during the morning." In this case, level 4 (high) is marked on the hazard map.
- "As a consequence of daytime warming and solar radiation, wet-snow avalanches can be expected again from the middle of the day below approximately 2400 m." (With no danger level indicated)
If the avalanche danger is assessed to be level 4 (high) or even level 5 (very high) at night, and then one level lower during the day, the morning rule is deviated from. As when transport routes are endangered, the avalanche danger is also significant at night, the higher avalanche level that applies during the night is given in the evening edition. In the morning edition this is then reduced to the level applying in the morning.
Double map
In typical springtime conditions, the danger of wet-snow avalanches along with daytime warming and solar radiation will increase significantly as the day progresses. During the day the danger of dry-snow avalanches will usually only change slightly in these conditions. Thus, while in the morning dry-snow avalanches are the main danger, in the afternoon the main danger is posed by wet-snow avalanches. In this situation, two maps show both the more favourable morning situation (dry-snow avalanches) and the unfavourable situation in the afternoon (wet-snow avalanches as the day progresses). The transition from one map to another cannot be pinned down to a specific time. It depends on the conditions and the altitude and also in particular the aspect. Whereas on east-facing slopes the danger of wet-snow avalanches will already increase during the morning, this usually occurs only later on west-facing slopes.
In special cases a double map is also used if there is a significant danger of gliding avalanches, and this danger is greater, over a wide area, than the danger of dry slab avalanches. It is worth noting in this case that these two dangers do not vary significantly during the day. Therefore, the two avalanche types are possible throughout the day.
Additional information
Avalanche danger and risk
The avalanche bulletin describes the avalanche danger, i.e. the likelihood of a release and the possible size of avalanches in a specific region, but the exact timing of an avalanche being triggered and the actual length of its starting zone and fracture depth cannot be determined.
An avalanche danger only becomes a risk (i.e. a probability that damage will occur) if endangered individuals, animals, forest, infrastructure etc. are in the area of the potential avalanche. In the avalanche bulletin, the avalanche danger is assessed regardless of the presence of endangered individuals or objects, i.e. on weekends with fine weather and weekdays with poor weather alike, and for populated areas and outlying terrain alike.
If an avalanche is released somewhere on a glacier during a snowstorm, there would obviously be an avalanche danger, but there would be no risk if there were no people in the surrounding area. If the same avalanche is released on a popular touring route on a sunny weekend, the risk would be much greater. The danger given in the avalanche bulletin may be the same in both cases, but the risk will be different.
Avalanches are a very special natural hazard, since unlike flash floods or earthquakes the 'perilous process' of an avalanche can be initiated by human activity. If anyone comes onto a dangerous slope, the artificial additional load can trigger an avalanche. In the case of more than 90% of the snow sports enthusiasts buried by a slab avalanche, they triggered the avalanche themselves or it was triggered by another member of their group.
Frequency of danger levels
The most frequently forecasted danger level in the Alps is level 2 (moderate), accounting for almost half of days (per warning region). It thus captures a day with 'average' avalanche danger. Level 3 (considerable) is forecasted on about one third of days. Danger level 4 (high) is only forecasted on 1% of winter days on average, while level 5 (very high) is forecasted even more rarely. In the Jura, the lower danger levels are more frequent.
The avalanche danger will change gradually whereas the scale has levels.
The danger scale has five levels. However, in reality the avalanche danger changes gradually. This means there is a range within each level.
Further Information
Division into regions
For the purposes of the avalanche bulletin, the Swiss Alps are divided in alignment with the warning regions used by the other federal natural hazard agencies (MeteoSwiss, Federal Office for the Environment (FOEN), Swiss Seismological Service (SED)). Groups consisting of several warning regions are formed, generally by applying climatological or political criteria, yielding overarching region names (see the maps below).
Great care is required when interpreting references in the context of backcountry tours in regional border areas. For example, the Jungfrau region is usually accessed from the north (northern flank of the Alps or Bernese Oberland), but the backcountry touring area mostly lies in Valais.
Marginal areas
There are no clearly defined boundaries between two regions with different danger assessments (e.g. different danger levels or different distributions of avalanche prone locations) but instead transitional areas which in many cases cannot be clearly assigned to either avalanche situation. This means that in a marginal area several kilometres wide, it can be assumed that either the more or the less favourite situation may apply.
Those undertaking backcountry ski or snowshoe hiking tours in such areas should therefore consult the avalanche bulletin for both regions in question.
Warning regions (the 149 smallest units)
Northern and southern flanks of the Alps, and the Jura
Main Alpine Ridge, Northern Alpine Ridge and Inneralpine Regions
The Main Alpine Ridge extends from Val Ferret via the Great St Bernard, Monte Rosa, Simplon, Gotthard, Lukmanier, San Bernardino, Maloja and Bernina passes to beyond Val Müstair.
The Northern Alpine Ridge covers a belt running from the Dent du Midi via the Wildstrubel and Jungfrau regions and Gotthard, Tödi and Vorab to Liechtenstein.
The Inneralpine Regions encompass the regions between the Main Alpine Ridge and the Northern Alpine Ridge, namely those of Central Valais, and parts of Northern and Central Grisons and Engadine.
Major political regions
The Grisons southern valleys consist of Val Mesolcina and Val Calanca (collectively Moesano), Val Bregaglia, Val Poschiavo and Val Müstair.
Political subregions 1
Political subregions 2
The Gotthard region consists of Obergoms, the Grimsel region, Urseren, Tavetsch, the Upper Valle Leventina and Val Bedretto.
Division into regions
For the purposes of the avalanche bulletin, the Swiss Alps are divided in alignment with the warning regions used by the other federal natural hazard agencies (MeteoSwiss, Federal Office for the Environment (FOEN), Swiss Seismological Service (SED)). Groups consisting of several warning regions are formed, generally by applying climatological or political criteria, yielding overarching region names (see the maps below).
Great care is required when interpreting references in the context of backcountry tours in regional border areas. For example, the Jungfrau region is usually accessed from the north (northern flank of the Alps or Bernese Oberland), but the backcountry touring area mostly lies in Valais.
Marginal areas
There are no clearly defined boundaries between two regions with different danger assessments (e.g. different danger levels or different distributions of avalanche prone locations) but instead transitional areas which in many cases cannot be clearly assigned to either avalanche situation. This means that in a marginal area several kilometres wide, it can be assumed that either the more or the less favourite situation may apply.
Those undertaking backcountry ski or snowshoe hiking tours in such areas should therefore consult the avalanche bulletin for both regions in question.
Warning regions (the 149 smallest units)
Northern and southern flanks of the Alps, and the Jura
Main Alpine Ridge, Northern Alpine Ridge and Inneralpine Regions
The Main Alpine Ridge extends from Val Ferret via the Great St Bernard, Monte Rosa, Simplon, Gotthard, Lukmanier, San Bernardino, Maloja and Bernina passes to beyond Val Müstair.
The Northern Alpine Ridge covers a belt running from the Dent du Midi via the Wildstrubel and Jungfrau regions and Gotthard, Tödi and Vorab to Liechtenstein.
The Inneralpine Regions encompass the regions between the Main Alpine Ridge and the Northern Alpine Ridge, namely those of Central Valais, and parts of Northern and Central Grisons and Engadine.
Major political regions
The Grisons southern valleys consist of Val Mesolcina and Val Calanca (collectively Moesano), Val Bregaglia, Val Poschiavo and Val Müstair.
Political subregions 1
Political subregions 2
The Gotthard region consists of Obergoms, the Grimsel region, Urseren, Tavetsch, the Upper Valle Leventina and Val Bedretto.
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