Zervreila

There is appreciably less snow in all regions than is usual for the time of year, especially at low and intermediate altitudes. The large amounts of fresh snow expected in the west and north over the next few days will fall on a snowpack that is unfavourable in many areas, the surface of the snowpack being faceted and loose in many places. In addition, there are distinct weak layers that are prone to triggering in the middle and lower parts of the snowpack, especially on western, northern and eastern slopes, particularly south of a line from the Rhone to the Rhine. North of this, the snowpack structure is somewhat more favourable, but even in these regions there are weak layers deeper in the old snowpack. Against this background, a rapid and significant increase in avalanche danger is in prospect, especially in the west and north.

Conditions were overcast on Tuesday, with light precipitation in almost all regions and with snowfall levels of between 1000 and 1500 m.

Fresh snow

The following amounts fell up to Tuesday afternoon:

• Jura, extreme west of Lower Valais, northern Lower Valais, Ticino: 5 to 15 cm
• elsewhere less or dry

Temperature

At midday at 2000 m, between -2°C in the north and -4°C in the south

Wind

Rising west to southwesterly, which, in the afternoon, was:

• moderate to strong in the Jura and on the northern flank of the Alps
• elsewhere light to moderate

In the north, conditions will be very cloudy with precipitation. This will be heaviest in northern and the extreme west of Lower Valais and in the Vaud Alps. The snowfall level will rise in the west overnight to Wednesday to 2000 m and then drop to 1300 m. In Valais, it will be lower at times. In the south, conditions will be very cloudy overnight to Wednesday with some precipitation, while daytime conditions will be quite sunny.

Fresh snow

Above 2200 m:

• northern and extreme west of Lower Valais, Vaud Alps: 50 to 80 cm
• remaining western and central parts of the northern flank of the Alps, rest of Valais: 30 to 50 cm
• eastern part of the northern flank of the Alps, southern Simplon region, northern Ticino, Surselva and Prättigau: 15 to 30 cm
• rest of Ticino and rest of Grisons: 5 to 15 cm

Temperature

At midday at 2000 m, between -2 °C in the north and 0 °C in the south

Wind

• Along the Prealps, strong to storm-force westerly to southwesterly in the west and north at high altitudes
• In Ticino and Grisons mostly moderate, initially from the southwest, then from the northwest

Thursday

In the north, conditions will continue to be very cloudy with persistent, heavy precipitation at times. The westerly wind will remain strong to storm-force, especially on the northern flank of the Alps and in the west. The amount of fresh snow is expected to be similar to that of the day before. The snowfall level will be between 1100 and 1300 m.

Avalanche danger will increase further generally, within level 4 in regions exposed to the most precipitation. An increased number of very large avalanches is expected in these regions, these being capable of descending right down into the valleys in the regular avalanche tracks and of endangering exposed transportation routes.

Friday

During the night to Friday, another 20 to 40 cm of snow will fall on the northern flank of the Alps, in Lower Valais and Prättigau, but less in the rest of Valais and Grisons. The snowfall level will be between 1000 and 1200 m. Conditions will be dry on the southern flank of the Alps. During the day, conditions will be cloudy with brighter intervals on the northern flank of the Alps and mostly sunny in Valais and the south. The westerly wind will subside significantly.

Avalanche danger will increase again somewhat overnight to Friday and may reach dangerlevel 4 even on the eastern part of the northern flank of the Alps and in northern Grisons. Very large avalanches are possible on the northern flank of the Alps, these being capable of descending right down into the valleys and endangering exposed transportation routes. In Grisons, on the other hand, the risk relates primarily to alpine snow sports terrain.