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Issuing office, publication frequency and validity

Issuing office

The editorial office of the Swiss avalanche bulletin is attached to the WSL Institute for Snow and Avalanche Research SLF in Davos. The avalanche warning service is the responsible body.

Publication frequency and validity

The avalanche warning service monitors the weather, snow and avalanche situation throughout the year. The frequency of publication and contents of the avalanche bulletin vary according to the seasonal conditions.

Winter

In the winter, the avalanche bulletin consists of two parts, as described below.

1. Danger map including danger description:
This part of the avalanche bulletin is issued twice daily in four languages (German, French, Italian, English). The 5 pm edition forecasts the avalanche danger for the next 24 hours – until 5 pm the next day.
The danger is reassessed in the mornings at 8 am, also in four languages (German, French, Italian, English). This forecast is valid until 5 pm.
In principle, a further assessment of the avalanche danger can be issued at any time, but this option is used only seldom.

2. Information on the snowpack and weather:
This part of the avalanche bulletin is produced only in the evenings. It is published at 5 pm in German and 6.00 pm in French, Italian and English, and is valid until 5 pm or 6.00 pm the next day.

Early and late winter season

As a general rule, an avalanche bulletin together with a danger map continues to be published for as long as the data resources allow a detailed assessment of the danger, including the danger levels. In the transitional periods between autumn and winter (typically from the end of October until early December) and between spring and summer (typically from the end of April until early June), the avalanche bulletin is published only in the evenings. The format and content are the same as in the winter. The bulletin may cover a period of several days, running until 5 pm on the indicated final day of validity.

The issue of bulletins with a danger map and the frequency of publication depend on the following factors in particular:

  • Information density: The SLF observers work every day from November 1 to April 30. Outside this period, fewer observations take place in the field. One reason for this reduction is the generally low level of snow sport activity. When direct observation is not taking place, information is obtained mostly by telephone as required and available. In some cases, observers cannot return to work until after November 1, once the mountain railway and cableway services are resumed. Likewise, their annual duty can end before April 30. In contrast, access to the network of automatic measuring stations is available during the summer as well.
  • Demand: Favourable snow conditions in large parts of the Swiss Alps and the seasonal reopening of the mountain railways and cableways increase the demand for daily avalanche bulletins.

Summer and autumn

From early summer until late autumn, avalanche bulletins are published in text form and generally without reference to danger levels only in the event of heavy snowfall. In the late autumn, bulletins are issued according to the snow situation and availability of information. These bulletins are published at 5 pm in German and around 6.00 pm in French, Italian and English, and are valid for one or several days, running until 5 pm on the indicated final day of validity.
The criteria for publishing an avalanche bulletin are satisfied if the forecast amount of new snow per precipitation event (normally 1 to 3 days) reaches one of the following values:

  • 20 cm at 2000 m or
  • 40 cm at 2500 m or
  • 60 cm at 3000 mm or
  • 80 cm at 3500 m

The indicated values are not exact, but only guidelines. They can vary, depending on the wind, temperature and the extent and properties of the existing snowpack. The snowfall event must affect at least an entire massif. Local snowfall, such as occur when triggered by individual thunderstorm cells, are disregarded.

Special case of Jura (and Sotto Ceneri)

The situation that prevails in Jura differs from that in the Alps insofar as an elevated avalanche danger occurs only on a few days and in a few places. When such a danger arises, however, it is not to be underestimated. For this reason, the daily avalanche bulletin indicates a danger level for the Jura only if the danger is categorised as considerable (level 3) or higher. A danger of the relevant magnitude occurs on around five days throughout the winter. All five danger levels are published for Sotto Ceneri. When there is no (more) snow lying on the ground, the indication of a danger level is omitted.