Val d'Hérens

Increase in avalanche danger, in particular in the west, and at elevated altitudes.

The wind slabs of the last few days are covered with new snow in some cases and therefore difficult to recognise. As a consequence of a gathering strong westerly wind, further wind slabs will form in the course of the day in particular in high Alpine regions. The fresh and older wind slabs are in some cases prone to triggering. Avalanches can additionally be released in the weakly bonded old snow in particular on west, north and east facing slopes. They can reach medium size. These avalanche prone locations are to be found especially in gullies and bowls. In high Alpine regions the avalanche prone locations are more prevalent and larger. Careful route selection is advisable.

Snowpack Snow depths at high altitudes are average for the time of year in the extreme west of Lower Valais, but below average in all other regions. At 2500 m the snow depth in western Lower Valais and in northwest Ticino is approximately 80 cm. Elsewhere 40 to 60 cm of snow is lying over a wide area, but the amounts are smaller in some parts of central Valais and central Grisons. In particular on shady slopes above approximately 2200 to 2400 m, weak faceted layers exist deeper in the snowpack over a wide area. In the west and on the main Alpine ridge from the Matterhorn into the Bernina region and to the south, these layers are already embedded so deep that even large avalanches are possible. The weekend’s fresh snow and snow drift accumulations remain prone to triggering in some places. As the southwesterly wind strengthens, on Tuesday both the fresh snow and loosely bonded old snow near the surface will be transported. Observed weather review Monday, 12.12.2022 The weather in the mountains was quite sunny, with high-altitude cloudbanks in the west in particular. Fresh snow - Temperature At midday at 2000 m: between -8 °C in the west and -11 °C in the east Wind Light to moderate from the west to northwest Weather forecast through Tuesday, 13.12.2022 During Monday night, cloud will build up from the west. During the day it will remain quite sunny in some parts of the far east and in the south, but elsewhere it will be mostly very cloudy. A little snow will fall in the west and north, even in the lowlands. In the afternoon the snowfall level will rise rapidly to approximately 1200 m. Fresh snow The outlook is uncertain. In the period from Monday evening until Tuesday afternoon the following amounts of snow will fall above approximately 1000 m:

• Lower Valais, Vaud Alps: 5 to 10 cm; on the border to France, up to 20 cm
• Rest of the northern flank of the Alps, Upper Valais, northern Ticino: locally up to 5 cm

Temperature Increasing from the west to reach between -3 °C in the west and -8 °C in the east, and -10 °C in the south at midday at 2000 m Wind

• During Tuesday night strengthening in the Alps, during the day moderate to strong in the northwest, and moderate in the northeast and south, from the southwest to west
• In the Jura initially a moderate bise wind, turning southwesterly and strengthening in the afternoon

Outlook through Thursday, 15.12.2022 Wednesday Wednesday will be mostly very cloudy; isolated bright spells are likely only in the south. Except in the regions south of the main Alpine ridge, some precipitation will fall over a wide area, chiefly in the far west. The amounts of precipitation remain uncertain: from Tuesday evening until Wednesday evening above approximately1800 m, 5 to 10 cm of snow could fall in the west and north, and 10 to 25 cm could fall in the far west. It will become mild and the snowfall level will rise towards 2000 m. At elevated altitudes the strong, sometimes storm force westerly wind will transport both the fresh snow and loosely bonded old snow. The danger of dry avalanches will increase over a wide area; depending on the amounts of fresh snow, the increase is likely to be most significant in the west. Rain will give rise to the likelihood of moist snow slides and gliding avalanches at intermediate altitudes, in the west and north in particular. Thursday The mostly dry second half of Wednesday night will be followed by variable to dense cloud cover on Thursday with light precipitation in the afternoon in particular. The snowfall level will drop in the north from 1800 m to approximately 1200 m. In the south, snow will fall even at low altitudes. The wind will be moderate to strong from the west, but from the southwest during the day. The avalanche danger will not change significantly.