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Extraordinary snowfall and very high avalanche danger

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Review of winter 2017/18


During the period of heavy snowfall in January, the SLF issued the highest possible avalanche danger level (5: very high) for widespread areas of the Swiss Alps. Although the numerous large and very large avalanches that occurred in this period caused some property damage, no injuries or deaths were reported. In the course of the winter, avalanches claimed the lives of 26 winter sport participants.


After three years with little snow, large quantities fell during the long winter of 2017/18, but only in the mountains. The snowfall was heavy in November, December and particularly in January, which was also an extremely warm month – the warmest January on record since MeteoSwiss commenced its measuring campaign in 1864. In consequence, most of the precipitation fell as rain at lower altitudes. In some regions in the period from the end of December until 23 January, between two-and-a-half and five metres of snow fell at high altitudes (above 2000 m). The most copious snowfall – in some places, amounts anticipated only once every 75 years – were registered in the Valais, which is generally rather dry. The long-standing measuring stations in Saas-Fee and Zermatt recorded the highest January total new snow values since measurements commenced more than 70 years ago (204 and 210 cm respectively).

From the perspective of the entire season, this was one of the snowiest winters of the last 30 years for altitude zones above 1500 m. The amount of snow lying below 1000 m, in contrast, was marginally half the average. The end of winter finally came in big steps: in an extremely warm April, the snow melted far more rapidly than usual.

Highest avalanche danger level in January

The SLF published for 22 January the highest possible avalanche danger level (5: very high) over a wide area for the first time since 1999. In the Valais and Grisons in particular, numerous large and, in some cases, very large avalanches released. The moist snow at intermediate altitudes slowed down the powder avalanches triggered at higher altitudes and thus prevented them from reaching any settlements. In some cases, however, the snow masses stopped only just short of buildings. Protective structural and organisational measures as well as land use planning proved effective overall. Although a high-tension power line, Alpine huts, roads and forests were among the assets that suffered damage during this period, no injuries or deaths occurred.

Nevertheless, the situation was measurably less extreme than the avalanche-fraught period in February 1999. In the 30 days prior to that particular avalanche event there was one-third more snowfall than in the avalanche period of this winter, moreover the snowfall extended down to low altitudes. The number and the magnitude of avalanches, as well as casualties and material damages, were substantially greater in 1999.

Avalanches claimed the lives of 26 winter sport participants

By the end of April the SLF had received reports of more than 250 destructive avalanches causing property damage or personal injury. A total of 26 people lost their lives in 19 avalanche accidents. The number of fatalities is higher than the long-term average, which stood at 21 on the 30 April cutoff date. The average number of avalanche victims in the course of one hydrological year (1 October until 30 September of the following year) is 22.

All avalanche victims in the winter of 2017/18 were taking part in winter sports. The accidents were caused not only by slab avalanches, but by two gliding avalanches as well. 18 of the victims (around two-thirds of the total) were engaged in backcountry tours; seven) in freeriding descents in outlying terrain; one person was caught in an avalanche while on an open winter hiking trail. Two larger avalanche accidents claimed the lives of three and four people, respectively.

Avalanche bulletins

The avalanche bulletin is still published daily. It is available at and with the SLF app “White Risk”. Subscribe to the push notifications sent by our app or to our text messaging service if you wish to be alerted to the publication of an avalanche bulletin during summer or autumn. (To order the service, text START SLF SOMMER to 9234. To unsubscribe, text STOP SLF SOMMER to 9234. Texts cost CHF 0.20 each.)

Mountain weather information is also available in the Alpine weather report, which is published in German by MeteoSwiss at, by phone on 0900 162 138 (CHF 1.20/min.), or with the MeteoSwiss app.

Further information

More detailed information can be found in our German or French Winterflash

Fatal avalanche accidents in the 2017/18 hydrological year

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Distribution of individual danger levels in winter 2017/18 (front bar) and long-term average (rear bar). The frequency of forecasts indicating danger levels 4 and 5 exceeded the long-term average.
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Avalanche accidents with fatalities in winter 2017/18 as of 30.4.2018 (mapping courtesy of Federal Office of Topography, copyright 2007, all rights reserved).