Wildhorn

High avalanche danger will be encountered over a wide area

High avalanche danger will be encountered over a wide area

The new snow and wind slabs are lying on the unfavourable surface of an old snowpack on west to north to east facing aspects. Avalanches can in many places be released, even by a single winter sport participant or triggered naturally. Avalanches can reach large size. The danger exists in particular in alpine snow sports terrain. Transportation routes situated at higher altitudes can be endangered occasionally. Backcountry touring and other off-piste activities call for extensive experience in the assessment of avalanche danger and great restraint. An increasing number of gliding avalanches are to be expected below approximately 1600 m.

Fresh snow and a strong west to northwesterly wind have given rise to extensive snow drift accumulations on the northern flank of the Alps and in northern Grisons. They will continue to increase in size on Wednesday. Increasingly large snow drift accumulations will form on Wednesday in Valais, central Grisons and Engadine as well. On west, north and east facing slopes sheltered from the wind, fresh snow and wind slab layers are lying on an unfavourable faceted old snow surface. In the Jura, on the northern flank of the Alps and in western Lower Valais, sometimes thick rain crusts dating from the final week of the old year exist deeper in the snowpack up to high altitudes. Below approximately 2700 m in these regions the thick crusts are stabilising the base of the snowpack, so that avalanches are unlikely to release the deep layers. From southern Valais through northern Ticino to Grisons, in contrast, in many cases the entire snowpack is faceted and interspersed only with thin melt-freeze crusts. In these regions in particular, avalanches can release the entire snowpack. On the northern flank of the Alps at intermediate altitudes, an increasing number of gliding avalanches are to be expected.

On Monday night, heavy snow fell at times in the north and northern Grisons. Snow fell in the other regions as well; only the far south remained dry and was partly sunny. After a break in precipitation, snow began to fall in the afternoon again in the north. The snowfall level was at low altitudes. Fresh snow: From Monday afternoon until Tuesday afternoon: - Northern Alpine ridge from Wildstrubel into Liechtenstein, northern Grisons: 40 to 60 cm - Rest of the northern flank of the Alps, northern Lower Valais, central Grisons, Lower Engadine: 20 to 40 cm - Jura, southern Valais excluding both the Visp valleys and the Simplon region, northern Ticino, northern Moesano, Upper Engadine, Val Müstair: 10 to 25 cm - Elsewhere: a few centimetres or none Temperature: At midday at 2000 m: between -10 °C in the north and -4 °C in the south Wind: - During the night over a wide area, moderate to strong from the northwest - During the day in the west, light to moderate from westerly directions, otherwise moderate, occasionally strong, from the northwest Snow will fall continuously in the north. In particular on the northern flank of the Alps from the Aletsch region into the Glarus Alps, the snowfall will also be heavy. On the northern flank of the Alps the snowfall level will rise to approximately 1200 m; in Valais and Grisons it will be at low altitudes. To the south of the main Alpine ridge it will remain dry and quite sunny with a strong northerly wind. Fresh snow: From Tuesday afternoon until Wednesday afternoon above 1500 m: - Northern Alpine ridge from the Aletsch region into the Glarus Alps: 50 to 80 cm - Rest of the northern flank of the Alps, Lower Valais, rest of Upper Valais excluding both Saastal and the southern Simplon region, also the rest of the Gotthard region, northern Grisons, Lower Engadine north of the Inn: 30 to 50 cm - Elsewhere: 15 to 30 cm over a wide area, otherwise smaller amounts or remaining dry Temperature: At midday at 2000 m: between -3 °C in the west and -6 °C in the east, around -2 °C in the south Wind: Strong, storm force at elevated altitudes and on the southern flank of the Alps, from the northwest to north

On Wednesday night a little more snow will fall in the north and east. Thursday and Friday will be quite sunny in the mountains. The zero degree level will rise very significantly on Thursday. In the middle of the day it will be approximately 2800 m in the west and approximately 2400 m in the east. On Friday it will fall to below 2000 m again. The danger of dry avalanches will decrease. In particular on Thursday, the conditions for snow sport outside marked and open pistes will remain critical over a wide area. On sunny slopes and generally at intermediate altitudes, wet snow and gliding avalanches are to be expected as the day progresses.