The warning regions used by MeteoSwiss and all the Swiss federal government's other official natural hazard warning authorities form the basis for the division into regions. 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 Eastern Bernese Oberland), but the backcountry touring area mostly lies in Northern Upper Valais.
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 both the more and the less favourite situations may apply.
Those undertaking backcountry ski or snowshoe hiking tours in such areas should therefore consult the avalanche bulletin for both regions in question.
SLF Warning regions on www.map.geo.admin.ch. Regional borders are meant to be seen as transitional zones. For that reason, the actual lines are generalized.
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.