Waadtländer Voralpen

In the west and in the north a considerable avalanche danger will be encountered over a wide area.

As a consequence of new snow and a strong to storm force westerly wind, avalanche prone wind slabs formed. Avalanches can in some places be released by a single winter sport participant and reach medium size. Backcountry touring calls for experience in the assessment of avalanche danger.

As a consequence of warming during the day and solar radiation moist snow slides are to be expected.

Avalanche bulletin survey: intermediate levels - helpful or confusing? Link to the survey in AvaBlog (on SLF-App WhiteRisk or at slf.ch)

Snowpack Fresh fallen snow and freshly generated snowdrift accumulations lie deposited on shady slopes atop an unfavourable old snowpack surface over widespread areas. Prior to this round of precipitation the snowpack at elevated altitudes was loosely-packed and faceted and evidenced large stretches of surface hoar in some places. On sunny slopes the old snowpack surface was significantly more favourably structured. For that reason, avalanches can trigger naturally with far greater ease on shady slopes or else in the major areas of precipitation. On the northern flank of the Alps and on north-facing slopes, in addition, expansively metamorphosed (faceted) layers lie deeply embedded inside the snowpack in some places. In the southern Valais and in Grisons, the entire old snowpack is expansively metamorphosed (faceted) and loosely-packed on north-facing slopes in some places. In the southern Valais more than anywhere else, avalanches can fracture down to deeply embedded layers inside the snowpack and subsequently grow to large size. Observed weather review Wednesday, 08.03.2023 On Wednesday evening in the western part of the Lower Valais more than anywhere else, there was a small amount of snowfall registered. Following a night of predominantly clear skies it was partly bright and clear in the southern regions and in Grisons during the daytime. In the remaining regions of Switzerland skies were heavily overcast and there was a small amount of precipitation. The snowfall level ascended swiftly from approximately 1200 m to nearly 1700 m. Fresh snow Between Tuesday afternoon and Wednesday afternoon the following amounts of fresh snow were registered above 2200 m:

• furthermost western part of Lower Valais: 15 to 25 cm;
• northern Alpine Ridge west of the Aare: 5 to 10 cm;
• in the remaining regions of Switzerland, only a few centimetres; in Grisons and in the Ticino it remained generally dry.

Temperature At midday at 2000 m, approximately 0 °C. Wind Winds were blowing at strong velocity, at storm-strength in some places, from southwesterly directions. Weather forecast through Thursday, 09.03.2023 During the nocturnal hours precipitation is anticipated over widespread areas, intensive precipitation in the western regions more than anywhere else. The snowfall level will lie between 1500 and 1800 m. During the daytime hours it will be dry and, in some places, sunny. In southern regions and the Valais, it will be quite sunny. Fresh snow Between Wednesday afternoon and Thursday morning, the following amounts of fresh snow are anticipated above 2200 m:

• furthermost western part of the Lower Valais, along the French border: 30 to 50 cm; as much as 60 cm from place to place;
• remaining parts of the Lower Valais, northern Alpine Ridge west of the Reuss: 15 to 30 cm;
• remaining parts of northern flank of the Alps, remaining parts of Valais: 10 to 20 cm;
• in the other regions of Switzerland, less; or else it will remain dry.

Temperature At midday at 2000 m, approximately 0 °C. Wind Winds will be blowing from westerly directions,

• at storm strength over far-reaching areas during the nighttime hours;
• slackening off slightly during the daytime hours; blowing at moderate to strong velocity.

Outlook through Saturday, 11.03.2023 Following the intermission in precipitation on Thursday, intensive precipitation will again set in from the west during the nocturnal hours on Thursday. Until Saturday evening, repeated bouts of precipitation are expected. The snowfall level will lie generally between 1000 and 1600 m. Most of the anticipated snowfall will be deposited in the furthermost region of Lower Valais: by Saturday evening approximately 100 cm. On the northern Alpine Ridge west of the Reuss and in the remaining parts of the Valais, 50 to 80 cm of fresh snowfall is expected, in the other regions of Switzerland, less. Amounts of precipitation and snowfall level values are still uncertain. The precipitation will be accompanied by strong to storm-velocity westerly winds. The avalanche danger levels are expected to increase further in the major areas of precipitation. Avalanche Danger Level 4 (high) could be reached on the northern Alpine Ridge west of the Reuss and in the remaining parts of the Valais. Particularly there, large-sized naturally triggered avalanches can be expected, even very-large sized avalanches in the Lower Valais. Exposed transportation routes can be placed at risk. In the southern and the inneralpine regions of Grisons, avalanche danger levels are not expected to change significantly.