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Avalanche bulletin through Saturday, 28 May 2016

Beware wet-snow avalanches

Edition: 27.5., 17:00 Next update: 28.5., 18:00 Validity

Beware wet-snow avalanches
Edition: 27.5.2016, 17:00 / Next update: 28.5.2016, 18:00
Avalanche danger
Wet-snow avalanches
On Saturday morning, the danger of wet-snow avalanches will swiftly increase. On north-facing slopes below approximately 3000 m, in the other aspects below approximately 3800 m, wet-snow avalanches can be expected. Particularly on north-facing slopes between 2400 and 3000 m, these triggered snow masses can fracture down to more deeply embedded layers inside the snowpack and subsequently grow to medium size. High-altitude, exposed transportation routes can in isolated cases be placed at risk. Backcountry skiing and freeriding tours in outlying terrain should be brought to a close early in the day. Also on exposed hiking routes at high altitude, avalanche hazards need to be taken into consideration.
Dry-snow avalanches
On Saturday, isolated avalanche prone locations for dry-snow avalanches are found on extremely steep north-facing slopes in high alpine regions more than anywhere else. The hazards of being swept along and falling need to be taken into consideration.
Snow and weather
Snowpack
The snow cover is thoroughly wet up to approximately 3000 m, including on north-facing slopes. During nights when skies are overcast and temperatures mild, the snowpack surface is barely able to freeze. The thin surface crust which forms subsequently melts rapidly in the early morning hours. Only on very steep north-facing slopes in high alpine regions is the snow still loosely packed in some places.
At 2500 m in the Valais, on the northern flank of the Alps, in the Gotthard region and in northern Grisons, the snowpack is 100 to 200 cm deep over widespread areas. In the remaining regions of Switzerland, the snowpack is approximately 100 cm deep.
Weather review to Thursday, 26 May:
On Thursday and Friday, skies were variably cloudy. The zero-degree level ascended to approximately 3400 m on Thursday, on Friday to approximately 3700 m. Winds were blowing from southerly directions, for the most part at light to moderate strength.
Weather forecast through Saturday, 28 May:
Skies on Friday night will be overcast for the most part. During the daytime on Saturday, it will turn quite sunny for a brief interim. During the afternoon, skies will again become increasingly overcast accompanied by showers in western and southern regions more than anywhere else. The snowfall level will be 3000 m. Winds will be southwesterly, blowing at moderate strength, but at strong velocity at altitudes around 4000 m.
Outlook
On Sunday morning as a result of foehn winds, there will be some final few bright intervals in eastern regions. In other regions, skies will be heavily overcast. In southern regions, intensive snowfall is anticipated. The snowfall level will descend incrementally down towards 2500 m. On Monday, skies will be overcast and a small amount of snowfall is expected over widespread areas above approximately 2200 m.
On Sunday, the hazards of dry-snow avalanches are expected to increase significantly in high alpine regions of the Main Alpine Ridge and southwards therefrom. On Monday, the hazards of dry-snow avalanches will increase somewhat in the other regions of Switzerland as well. Wet-snow avalanches can be expected on Sunday as a consequence of rainfall, on north-facing slopes at high altitudes more than anywhere else. On Monday, the danger of wet-snow avalanches will diminish somewhat as a result of lower temperatures.

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