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Avalanche bulletin through Friday, 24 March 2017

In the south a high avalanche danger will be encountered in some regions

Edition: 23.3., 17:00 Next update: 24.3., 18:00 Validity

In the south a high avalanche danger will be encountered in some regions
Edition: 23.3.2017, 17:00 / Next update: 24.3.2017, 18:00
Snowpack
In the major areas of precipitation at high altitudes, wide-ranging snowdrift accumulations have formed. As a result of the fresh fallen snow and strong-velocity southerly winds, the snowdrift accumulations continue to grow in frequency, spread and size. The fresh fallen and freshly drifted snow is prone to triggering; moreover, avalanches can fracture down to more deeply embedded layers inside the snow cover and sweep away the entire snowpack. Large-sized avalanches continue to be possible. Also in the remaining regions of Switzerland, the previously small-sized snowdrift accumulations are continuing to grow in frequency and size as a result of the strong-velocity southerly winds.
More deeply embedded inside the snow cover, particularly on west, north and east-facing slopes above approximately 2200 m, weakened layers consisting of faceted-crystal snow are evident. In the inneralpine regions of the Valais and Grisons, these weak layers are blanketed over by only shallow snow and in some places can be triggered by skiers or freeriders.
On north-facing slopes the snow cover is thoroughly wet up to approximately 2000 m; in the western regions of Switzerland up to approximately 2500 m. On steep, south-facing slopes the snowpack is thoroughly wet up to nearly 3000 m. In steep avalanche pathways which have not yet discharged, wet-snow avalanches continue to be possible which, in some cases, could sweep along the entire snowpack.
Observed weather on Thursday, 23.3.2017
On Wednesday night skies were for the most part heavily overcast and there was snowfall registered over widespread areas. In the Urner Alps, in the Gotthard region and southwards therefrom, the snowfall was very intensive. During the daytime on Thursday, skies on the Main Alpine Ridge and southwards therefrom were heavily overcast, accompanied by snowfall which subsequently slackened off somewhat. The snowfall level was between 1400 and 1800 m. North of the Main Alpine Ridge it was partly sunny, in northeastern regions predominantly sunny.
Fresh snow
Since the beginning of this period of precipitation on Tuesday evening until Thursday evening, the following amounts of fresh fallen snow have been registered in southern regions above approximately 2200 m, and in northern regions above approximately 1900 m:
  • northwestern Ticino, Urseren: 60 to 100 cm;
  • remaining parts of the Main Alpine Ridge from the Simplon region as far as San Bernardino, remaining sectors of the southern flank of the Alps, remaining parts of the Urner Alps: 40 to 60 cm;
  • in the regions directly bordering: 20 to 40 cm; in other regions of Switzerland, 5 to 20 cm over widespread areas.
Temperature
At midday at 2000 m, between +5 °C in western regions; +3 °C in eastern regions; and 0 °C in southern regions.
Wind
  • Winds were southerly during the night, blowing at light to moderate strength, to some extent at strong velocity at high altitudes and in some southern regions;
  • During the daytime, winds were southerly, blowing predominantly at moderate to strong velocity, in high alpine regions to some extent at storm strength.
Weather forecast through Friday, 24.3.2017
On the Main Alpine Ridge and southwards therefrom, skies will be heavily overcast. The precipitation is expected to continue. The snowfall level will be at 1500 to 2000 m. In northern regions, skies during the night will be overcast by and large. During the daytime it will be partly sunny, accompanied by cloudbanks. As a result of foehn wind, it will be very mild.
Fresh snow
Between Thursday evening and Friday evening, the following amounts of new fallen snow are anticipated above approximately 2000 m:
  • Upper Valais part of the Main Alpine Ridge, southern Urseren, western Ticino: 15 to 30 cm;
  • remaining parts of the Main Alpine Ridge from the Great St. Bernard Pass into the Bernina region, remaining sectors of the southern flank of the Alps: 5 to 15 cm.
Temperature
At midday at 2000 m, +6 °C in northern regions and +2 °C in southern regions.
Wind
Winds will be southerly to southeasterly, blowing at moderate to strong velocity.
Outlook through Sunday, 26.3.2017
Saturday
In southern regions skies will be variably cloudy accompanied by bright intervals and intermittent snowfall above approximately 2000 m. In northern regions it will be partly sunny accompanied by cloudbanks. The danger of dry-snow avalanches will diminish. The danger of wet-snow avalanches will increase during the course of the day.
Sunday
Skies will be heavily overcast for the most part, accompanied by precipitation whose distribution is uncertain. The snowfall level is expected to descend from 2000 m down to 1000 m. The danger of dry-snow avalanches could increase from place to place as a result of the fresh fallen snow. The danger of wet-snow avalanches will diminish.