südliches Urseren

As a consequence of rain a considerable danger of wet avalanches will be encountered over a wide area.

As a consequence of the rain wet avalanches are to be expected. They can release deeper layers of the snowpack and reach large size, especially on steep north facing slopes. The conditions are unfavourable for backcountry touring.

The fresh and older wind slabs are in some cases prone to triggering. Dry avalanches can additionally be released in deeper layers in isolated cases. Caution is to be exercised in particular in areas where the snow cover is rather shallow, as well as on very steep north and east facing slopes above approximately 2800 m.

Snowpack On north-facing high-altitude slopes more than anywhere else, there are snowdrift accumulations from place to place and near-surface weak layers which are frequently prone to triggering. As a consequence of the cooler temperatures at the beginning of this week, the process of the snow cover becoming thoroughly wet was initially brought to a temporary halt. East-facing, south-facing and west-facing slopes were already thoroughly wet up to over 3000 m. On north-facing slopes the process was halted when the snowpack was thoroughly wet up to between 2000 and 2500 m. Since Wednesday as a result of higher temperatures, the near-surface layers of the snow cover have become increasingly moist. As a result of the rainfall, water now seeps further down into the snow cover. This weakens more deeply embedded layers in the snowpack which are becoming wet for the first time this spring. At heightened altitudes on the northern flank of the Alps and in northern Grisons, the snow depths correspond to long-term medium values, in the Valais snow depths lie slightly above average. Further to the south, snow depths continue to be significantly below average. Observed weather review Friday, 28.04.2023 Skies were heavily overcast for the most part, and in the northern and the eastern regions there was a small amount of precipitation from place to place. The snowfall level during the nocturnal hours lay at 2000 to 2300 m, during the daytime hours the snowfall level ascended in western regions to 2700 m and in eastern regions to 2500 m. In the southern Valais and on the southern flank of the Alps it turned partly sunny during the course of the day. Fresh snow Between Thursday evening and Friday afternoon, the following amounts of fresh snow were registered above approximately 2800 m:

• in the eastern sector of the northern flank of the Alps, Prättigau, Silvretta, Samnaun: 5 to 15 cm;
• in the remaining regions of Switzerland, less; or else it remained dry.

In the eastern Prealps there was 10 to 30 mm of rainfall registered. Temperature At midday at 2000 m, +8 °C in the Valais, in other parts of Switzerland between +5 °C in the northern regions and +3 °C in the southern regions. Wind Winds were blowing at light to moderate strength, blowing at moderate to strong velocity in some places at elevated altitudes, from westerly directions. Weather forecast through Saturday, 29.04.2023 During the nighttime hours on Friday, precipitation is anticipated over widespread areas, only in the furthermost southern regions is it expected to remain dry. During the daytime hours on Saturday in the western and the southern regions, skies will be heavily overcast for the most part and intermittent precipitation is anticipated, even thunderstorms are possible. In the northeastern regions it will still be partly sunny during the morning, subsequently skies will become overcast, accompanied by showers. The snowfall level on Friday evening will lie at 2600 to 2800 m and subsequently descend down to approximately 2500 m on Saturday. Fresh snow The forecast of precipitation is still uncertain, presumably between Friday evening and Saturday afternoon the following amounts of fresh snow can be expected above approximately 3000 m:

• furthermost western part of the Lower Valais, northern Alpine Ridge from Les Diablerets as far as Sustenhorn: 15 to 30 cm;
• northern flank of the Alps east of the Sustenhorn, remaining parts of Valais, northern Prättigau: 10 to 20 cm;
• in the other regions of Switzerland, only a few centimetres.

Below approximately 2500 m this entire round of precipitation will fall as rain. Temperature At midday at 2000 m, +6 °C. Wind Winds will be blowing from westerly to northwesterly directions,

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

Outlook through Monday, 01.05.2023 Uncertain development of approaching weather conditions on both days: On Sunday, following a night of partly overcast skies, it will still be partly sunny in the eastern regions during the morning; in the other regions of Switzerland skies will be predominantly overcast, accompanied by showers and, in some places, by thunderstorms. The snowfall level will lie at 2200 to 2400 m. Winds are expected to shift to southerly and be blowing at light to moderate strength. On Sunday night and during the daytime on Monday, skies will be heavily overcast accompanied by some precipitation. The snowfall level is expected to descend down to approximately 1900 m. Particularly in the southern and the eastern regions, a moderate to strong velocity southerly wind will be blowing intermittently at heightened altitudes. In the western regions and on the Main Alpine Ridge, 15 to 30 cm of fresh snowfall is anticipated at elevated altitudes, possibly greater amounts of fresh snow in the Upper Valais sector of the Main Alpine Ridge. Avalanche danger levels are not expected to change significantly on Sunday. On Monday, the danger of dry-snow avalanches will increase over widespread areas, perhaps significantly so in the western and the southern regions. The danger of wet-snow avalanches is expected to remain at heightened levels on Sunday, subsequently diminish during the course of the day on Monday.