Monthey-Val d'Illiez

Increase in avalanche danger as a consequence of new snow and strong wind.

As a consequence of new snow and a strong to storm force westerly wind, easily released wind slabs will form. These will be deposited on the unfavourable surface of an old snowpack in particular on shady slopes. Avalanches can reach medium size. Danger level 3 (considerable) will be reached in the late morning probably. In the course of the day the wind slabs will increase in size additionally. An increasing number of natural avalanches are possible in the afternoon. Backcountry touring calls for experience in the assessment of avalanche danger.

As a consequence of the rain more frequent small to medium-sized wet avalanches are to be expected below approximately 2000 m.

Snowpack The old snowpack was loosely bonded and faceted on wind-protected shady slopes at high altitudes. A thick layer of surface hoar has also formed here over a wide area. Fresh snow and snow drift accumulations can easily be released in the affected places. On sunny slopes the old snowpack was much more favourable. In addition, on north facing slopes on the northern flank of the Alps, faceted layers exist in the snowpack in some places. On north facing slopes in southern Valais and in Grisons, furthermore, the entire old snowpack is faceted and loosely bonded over a wide area. The snow depths in the Swiss Alps remain well below average. On the flat sites occupied by the measuring stations at high altitudes, the values are only around half those usually recorded. Observed weather review Tuesday, 07.03.2023 The night was partly clear. In the south and in Grisons a few snowflakes fell locally. During the day it was quite sunny in the mountains despite high-altitude cloudbanks. Fresh snow - Temperature At midday at 2000 m: about 0 °C in the west and -2 °C in the other regions Wind Moderate to strong southwesterly Weather forecast through Wednesday, 08.03.2023 On Tuesday evening a little precipitation will fall over a wide area before the skies clear again during the night. During the day there will be precipitation in the west and north. The snowfall level will be approximately 1000 m on Tuesday evening and rise towards 1800 m on Wednesday. In the south and in the inneralpine regions of Grisons it will be partly sunny. Fresh snow From Tuesday afternoon until Wednesday afternoon above 2200 m:

• Extreme west of Lower Valais along the border to France: 20 to 30 cm
• Vaud Alps, rest of Valais, northern Alpine ridge west of the Reuss: 10 to 15 cm
• Elsewhere: a few centimetres or none

Temperature At midday at 2000 m: between 0 °C in the north and -2 °C in the south Wind Strong, increasingly storm force from the west Outlook through Friday, 10.03.2023 Thursday On Wednesday night precipitation will fall over a wide area in the west and north. 30 to 50 cm of snow is to be expected in western Lower Valais, and 10 to 30 cm in northern Valais and in the western part of the northern flank of the Alps. The snowfall level will rise to 2000 metres for a while during the night before falling back towards 1500 metres during the day. The precipitation will be accompanied by a strong to storm force westerly wind. The afternoon will be mostly dry and partly sunny. In the south there will be hardly any precipitation and it will be quite sunny throughout the day. In the extreme west of Lower Valais during the night, an increasing number of medium-sized and large natural avalanches are to be expected. Here, danger level 4 (high) could be reached during Wednesday night. For the time being, the danger applies primarily to alpine snow sports terrain. Transportation routes are exposed to very little danger. The avalanche danger will increase in the other regions as well, but only slightly in the south and in the inneralpine regions of Grisons. Friday Further precipitation will fall from Thursday evening, again most heavily in the west. 30 to 50 cm of snow is to be expected in the extreme west and the north of Lower Valais, and 15 to 30 cm in the rest of Valais and the Vaud Alps. The snowfall level will be between 1200 and 1600 m. The precipitation will be accompanied by a strong to storm force westerly wind. In the south and in the inneralpine regions of Grisons, hardly any snow will fall and it will be partly sunny. In the extreme west of Lower Valais, numerous large and isolated very large natural avalanches are to be expected. Exposed transportation routes can be endangered. In northern Valais and the Vaud Alps the avalanche danger will also increase significantly. Danger level 4 (high) can be reached in these regions as well. Otherwise the avalanche danger will increase a little over a wide area, but it will not change significantly in the south or in the inneralpine regions of Grisons.