Considerable avalanche danger will be encountered in some regions
Edition: 12.5.2021, 17:00 / Next update: 13.5.2021, 18:00
Snowpack
On the Main Alpine Ridge from the Great St. Bernard to the Bernina Pass and southwards therefrom, wide-ranging snowdrift accumulations have been generated at elevated altitudes over the course of the last week in the wake of large quantities of fresh snow accompanied by storm-strength southerly winds. These snowdrifts are still prone to triggering in some places. In the northern regions, generally small-sized snowdrift accumulations were generated on Tuesday during the nighttime hours as a result of the fresh snow and northerly winds.
Below 2500 m the snow cover has been weakened due to intensive rainfall this week. On north-facing slopes below 2400 m more than anywhere else, some large-sized and, in isolated cases, very large-sized wet-snow avalanches have been observed. As of the termination of this period of precipitation and the subsequently dropping temperatures, activity of wet-snow avalanches has diminished. During the nocturnal hours on Wednesday night, amid overcast skies, the moist snowpack surface at intermediate and high altitudes will hardly be able to freeze. Isolated wet-snow and gliding avalanches continue to be possible.
In general, the Avalanche Warning Services have little information currently available from outlying regions. For that reason, avalanche danger levels need to be examined especially carefully on-site.
Observed weather on Wednesday, 12.05.2021
In the southern regions and the Valais, the snowfall came to a close during the early part of Tuesday night, in the northern regions during the course of the morning on Wednesday. The snowfall level descended from 2000 down to 1500 m on Tuesday night. During the daytime on Wednesday it was partly sunny in the southern and western regions, in the other regions of Switzerland skies were heavily overcast and there were isolated showers during the course of the afternoon.
Fresh snow
Between Tuesday afternoon and Wednesday afternoon above approximately 2200 m, the following amounts of fresh snow were registered:
  • northern flank of the Alps from the Jungfrau as far as the Säntis, Grisons: 15 to 25 cm;
  • Valais and remaining parts of the western sector of the northern flank of the Alps: 5 to 15 cm;
  • in the other regions of Switzerland, only a few centimetres.
All in all, since the beginning of this period of precipitation on Sunday evening until Wednesday afternoon, the following amounts of fresh snow have been registered above approximately 2800 m:
  • Main Alpine Ridge along the Italian border from the Simplon region as far as Nufenen Pass and Bedretto valley: 90 to 130 cm;
  • remaining parts of northern Ticino, southern Urseren, Zervreila, Rheinwald, Moesano, Val Bregaglia and the Bernina region: 60 to 90 cm;
  • remaining parts of the Main Alpine Ridge from the Great St. Bernard as far as Upper Engadine, northern Alpine Ridge from the Jungfrau to the Titlis: 30 to 60 cm;
  • remaining parts of Valais, remaining parts of the northern flank of the Alps, remaining parts of Grisons: 10 to 30 cm.
Temperature
At midday at 2000 m, 0 °C in the northern regions and +4 °C in the southern regions.
Wind
  • During the nocturnal hours on Tuesday night in the southern and eastern regions, winds were blowing at moderate to strong velocity, in the other regions at light to moderate strength, from northerly directions;
  • during the daytime hours on Wednesday winds slackened off, blowing generally at light strength during the afternoon.
Weather forecast through Thursday, 13.05.2021
On Ascension Day, weather conditions will be variably cloudy to heavily overcast, and from the west some showers are anticipated. The snowfall level will lie at 1500 m. In the southern regions in the early morning hours, and in the western regions in the afternoon, sunny intervals are possible.
Fresh snow
Between Wednesday afternoon and Thursday afternoon, the following amounts of fresh snow are anticipated above approximately 2000 m:
  • northern flank of the Alps, Valais, northern Grisons, Silvretta, Samnaun: 5 to 10 cm; in the Monte Rosa region as much as 15 cm;
  • in the remaining regions of Switzerland, only a few centimetres, or else it will remain dry.
Temperature
At midday at 2000 m, between -2 °C in the northwestern regions and +4 °C in the southeastern regions.
Wind
  • Winds in the northern regions will be light, blowing intermittently at moderate strength, from westerly directions;
  • in the southern regions winds will be light, intermittently blowing at moderate strength, from northerly directions.
Outlook through Saturday, 15.05.2021
On both days, skies will be variably cloudy accompanied by short sunny intervals and, from region to region, showers. On Friday afternoon, isolated thunderstorms are also possible. The snowfall level will lie at 1500 m. In the northern regions a light-to-moderate westerly wind will be blowing; in the southern regions, a light-to-moderate wind from northerly directions. Avalanche danger levels are expected to gradually diminish.