südliches Urseren

Considerable danger of dry and wet avalanches will be encountered in some regions.

The wind slabs of the last few days are in some cases still prone to triggering. They are to be evaluated with care and prudence in very steep terrain. The number and size of avalanche prone locations will increase with altitude. Additionally in isolated cases avalanches can penetrate near-ground layers of the snowpack and reach large size. Caution is to be exercised in particular on very steep north facing slopes.

Snowpack Fresh snowdrift accumulations have been generated in high alpine regions as a consequence of fresh fallen snow and northwesterly winds. Above approximately 2800 m more than anywhere else, these snowdrift accumulations as well as near-surface layers are prone to triggering in some places. East-facing, south-facing and west-facing slopes are already thoroughly wet up to over 3000 m. As a result of the rainfall from Friday and Saturday, also north-facing slopes were made thoroughly wet up to approximately 2500 m, and thereby weakened. Increasingly frequent wet-snow and gliding avalanches were triggered, particularly in the major areas of precipitation of the west and the north. During the nocturnal hours on Saturday, a melt-freeze crust which is capable of bearing loads is expected to form in some places. Attention needs to be drawn to the fact that on high-altitude north-facing slopes, wet slab avalanches can be triggered by persons in some places, in the inneralpine regions of the Valais and Grisons more than anywhere else. Observed weather review Saturday, 29.04.2023 During the nighttime hours on Friday in the northern and the western regions, there was precipitation registered over widespread areas. During the daytime hours on Saturday, conditions turned increasingly sunny, accompanied by heavy convective cloud build-up and showers in the Prealps more than anywhere else. The snowfall level ascended to 2800 m on Friday evening, subsequently descended to 2400 to 2600 m during the night. Fresh snow Between Thursday evening and Saturday midday, the following amounts of fresh snow were registered above approximately 2800 m:

• northern Alpine Ridge from Les Diablerets as far as Sustenhorn, Lower Valais: 15 to 30 cm, as much as 40 cm from place to place;
• northern Alpine Ridge east of Sustenhorn, southern Lower Valais, northern Grisons, Lower Engadine: 10 to 20 cm;
• in the remaining regions of Switzerland, only a few centimetres; or else it remained dry.

Below approximately 2400 m, this entire round of precipitation fell as rain: in the Prealps 20 to 30 mm, in the eastern Prealps as much as 60 mm from place to place. Temperature At midday at 2000 m, +5 °C in the northern regions and +8 °C in the southern regions. Wind Winds were blowing from westerly to northwesterly directions,

• at moderate to strong velocity at heightened altitudes during Friday night;
• blowing at light to moderate strength during the daytime hours on Saturday.

Weather forecast through Sunday, 30.04.2023 During the nocturnal hours on Saturday, skies are expected to be predominantly clear, clouds will move in from the southwest as morning approaches. During the morning hours in the eastern regions it will be sunny to start with, subsequently skies will become increasingly overcast during the course of the day. In the western and the southern regions it will be predominantly overcast accompanied by isolated bright intervals and also showers. The snowfall level will lie at 2200 to 2500 m. Fresh snow Between Saturday evening and Sunday afternoon, the following amounts of fresh snow are anticipated above approximately 2600 m:

• northern flank of the Alps, Valais, Ticino: 5 to 10 cm;
• in the remaining regions of Switzerland, only a few centimetres; or else it will remain dry.

Temperature At midday at 2000 m, +6 °C in the northern reigons and +4 °C in the southern regions. Wind

• Winds during the nighttime hours on Saturday will be westerly to northerly to begin with, blowing at light to moderate strength, subsequently shifting to southerly;
• during the daytime hours blowing at light strength from southerly directions.

Outlook through Tuesday, 02.05.2023 Monday During the nocturnal hours on Sunday and during the daytime on Monday, skies will be heavily overcast for the most part, accompanied by precipitation in the western and the southern regions more than anywhere else. The snowfall level is expected to descend to approximately 1900 m. At heightened altitudes, a moderate to strong-velocity southerly wind will be blowing intermittently. In the western and the southern regions, 20 to 40 cm of fresh snow is expected to fall at elevated altitudes, possibly up to 50 to 60 cm of fresh snowfall in the Upper Valais sector of the Main Alpine Ridge on the Italian border and in the northwestern part of Ticino. The danger of dry-snow avalanches is expected to increase over widespread areas, significantly so in the western and the southern regions from place to place. The danger of wet-snow avalanches will decrease during the course of the day on Monday. Tuesday During the nighttime hours on Monday, precipitation is expected over far-reaching areas. During the daytime hours on Tuesday in the northern and the eastern regions, there will still be additional precipitation. The snowfall level will lie at 2000 m. At heightened altitudes in the northern regions, 15 to 30 cm of fresh fallen snow is possible. In the southern and the western regions, it will presumably become increasingly sunny during the course of the day on Tuesday. Avalanche danger levels are expected to increase at high altitudes in the northern regions. In the southern and the western regions, danger of dry-snow avalanches is expected to diminish somewhat. During the course of the day, moist slides can be expected to trigger from the fresh fallen snow.