Génépi

In Valais a high avalanche danger will be encountered over a wide area.

As a consequence of new snow and stormy weather the already large wind slabs will increase in size additionally. The new snow and wind slabs are lying on the unfavourable surface of an old snowpack in particular on shady slopes. Numerous medium-sized to large natural avalanches are to be expected. To some extent avalanches can also be triggered in deep layers. In the typical avalanche paths avalanches can in isolated cases reach intermediate altitudes and endanger transportation routes that are exposed. The conditions are dangerous for backcountry touring and other off-piste activities outside marked and open pistes.

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

Snowpack As a consequence of heavy snowfall over widespread areas accompanied by storm-strength westerly winds, the snowdrift accumulations are continuing to grow in number and in size in the western and the northern regions. Fresh fallen snow and freshly generated snowdrift accumulations lie deposited on shady slopes atop an unfavourable old snowpack surface over widespread areas. Avalanches can be very easily triggered in those locations or even, in the major areas of precipitation, trigger naturally. On sunny slopes the old snowpack surface was more favourably structured prior to the precipitation. On the northern flank of the Alps on north-facing slopes, furthermore, there are expansively metamorphosed (faceted) layers deeply embedded inside the snow cover in some places. In the southern Valais and in Grisons on north-facing slopes over widespread areas, the entire old snowpack is expansively metamorphosed (faceted) and loosely-packed. In the southern Valais more than anywhere else, avalanches can fracture down to deeply embedded layers in the snowpack. Observed weather review Friday, 10.03.2023 There was precipitation registered over far-reaching areas, most of it fell in the western regions. The snowfall level lay between 1300 and 1700 m. In the southern regions it was partly sunny. Fresh snow Between Thursday evening and Friday afternoon the following amounts of fresh snow were registered above 2000 m:

• northern and furthermost western parts of the Lower Valais: 25 to 45 cm;
• Vaud Alps, remaining parts of the northern flank of the Alps, northern Upper Valais as well as remaining parts of the Lower Valais: 15 to 25 cm;
• Jura region, remaining parts of the northern flank of the Alps, remaining parts of the Valais, Main Alpine Ridge from San Bernadino as far as Bernina Pass: 5 to 15 cm;
• in the remaining regions of Switzerland, only a few centimetres.

Thus, since the beginning of the most recent period of precipitation on Tuesday evening, the following overall amounts of fresh snow have been registered above approximately 2200 m:

• furthermost western part of the Lower Valais: 60 to 80 cm;
• remaining parts of Lower Valais, northern Valais, Binntal, Goms: 40 to 60 cm;
• Upper Valais, remaining parts of the northern Alpine Ridge west of the Aare: 20 to 40 cm;
• in the other regions of Switzerland, less.

Temperature At midday at 2000 m, -2 °C in the western and the northern regions, +1 °C in the southern and the eastern regions. Wind Winds were blowing from westerly directions,

• at strong velocity in the northern regions and in general at heightened altitudes;
• in the other regions of Switzerland, blowing predominantly at moderate strength.

Weather forecast through Saturday, 11.03.2023 Precipitation is anticipated over widespread areas, expected to be intensive in the western and the northern regions. The snowfall level during the nocturnal hours will be at low lying areas, subsequently will ascend during the course of the day in western regions to nearly 1500 m. In the southern regions it is expected to be predominantly sunny during the daytime hours. Fresh snow Between Friday afternoon and Saturday afternoon, the following amounts of fresh snow are anticipated above 1800 m:

• Valais not including Goms, northern Alpine Ridge west of the Reuss: 30 to 50 cm; as much as 70 cm in the furthermost western regions;
• remaining parts of the northern flank of the Alps, Goms: 15 to 30 cm;
• in the other regions of Switzerland, 5 to 15 cm over widespread areas; in the southern regions it is expected to remain dry.

Temperature At midday at 2000 m, between 0 °C in the southwestern regions and -5 °C in the northeastern regions. Wind Winds in the northern regions

• will be blowing at strong velocity at heightened altitudes, intermittently blowing at storm strength, from westerly directions;
• in the other regions of Switzerland blowing predominantly at moderate strength.

Winds in the southern regions

• will be blowing at strong velocity, at storm-strength at elevated altitudes, from northwesterly directions.

Outlook through Monday, 13.03.2023 Sunday On Sunday, skies will be heavily overcast for the most part and further precipitation is anticipated until midday. The snowfall level will lie at approximately 1500 m. In the Valais and well as on the northern flank of the Alps and in northern Grisons, approximately 15 to 30 cm of fresh snow is expected to fall, in the other regions, less. In the northern regions the storm-strength westerly winds will slacken off during the course of the day. In the southern regions it will be predominantly sunny as a result of the often strong-velocity northerly winds. As the precipitation rounds to a close and the stormy winds slacken off during the course of the day, naturally triggered avalanche activity will decrease. For winter sports enthusiasts who are active in backcountry apart from secured ski runs, the avalanche situation in the western and the northern regions remains critical over widespread areas. As a consequence of solar radiation and higher daytime temperatures, moist avalanches can be expected to trigger from the fresh fallen snow on sunny slopes. In the southern regions and in the Grisons, the avalanche situation is more favourable. Monday During the daytime hours it is expected to be quite sunny. Temperatures will rise significantly, the zero-degree level will ascend to nearly 3000 m. Winds in the northern regions will be blowing at strong velocity, in the southern regions at moderate strength, from westerly directions. The danger of dry-snow avalanches is expected to decrease in the western and the northern regions, however will remain treacherous for winter sports enthusiasts in backcountry terrain away from secured ski runs. As a result of solar radiation and rising daytime temperatures, most avalanches can be expected to release from the fresh fallen snow on sunny slopes in the major areas of precipitation.