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Full avalanche bulletin PDF

Avalanche bulletin through Tuesday, 5 May 2015

Wet snow avalanches pose main danger

Edition: 4.5., 17:00 Next update: 5.5., 18:00 Validity

Wet snow avalanches pose main danger
Edition: 4.5.2015, 17:00 / Next update: 5.5.2015, 18:00
Avalanche danger
Danger of wet snow avalanches
Locations prone to wet snow avalanches are to be found below approximately 3000 m in particular. During the night the snowpack, which is moist all the way through, will barely be able to freeze and will remain unstable. As a consequence of solar radiation, warm temperatures and rain in the afternoon in the west, natural wet snow avalanches can still occur. In particular in Valais and in Grisons, but to some extent on the northern flank of the Alps as well, these avalanches can release the entire snowpack and, in isolated cases, reach a large size. This applies in particular to west to north to east facing steep slopes between approximately 2500 and 3000 m.
Danger of dry avalanches
Locations prone to dry avalanches are to be found above approximately 3000 m in particular. Relatively recent snow drift accumulations are prone to triggering in some cases. These are large on the northern flank of the Alps and in Valais, but mostly small in the other regions. Careful route selection is important.
Snow and weather
Below approximately 3000 m in the north and west in particular the snowpack has been weakened by rain, which was heavy in some cases. In recent days numerous wet snow avalanches, some of them large, have been released in the north and in Valais.
In the high Alpine regions, fresh and older snow drift accumulations are prone to triggering in some cases.
The snow line is approximately 1700 m over a wide area on north facing slopes, and approximately 2000 m in Valais. On south facing slopes it is between 2000 and 2500 m.
Weather review
On Sunday night rain fell up to approximately 3000 m. The rainfall was heavy in the west and north. The precipitation eased during the day. It was cloudy.
From Saturday evening until Monday morning, the following amounts of rain fell: 50 to 80 mm over a wide area in the western part of the northern flank of the Alps and in Lower Valais, 30 to 50 mm over a wide area in the remaining parts of the northern flank of the Alps and of Valais. Much smaller amounts, namely 5 to 10 mm, fell in Grisons and Ticino. Above approximately 3300 m, precipitation in these quantities fell as snow, but measured in centimetres.
The wind was light to moderate from the southwest.
Weather outlook
Monday night will be overcast. During the day in the east the foehn wind will give rise to prolonged bright spells. In the afternoon showers and thunderstorms will arrive from the west. The south will be mostly cloudy. Above approximately 3000 m, 5 to 10 cm of snow will fall in the west, and a few centimetres of snow will fall over wide area elsewhere. The east and south will remain dry.
At elevated altitudes the wind will be moderate to strong from the southwest.
On Tuesday night, snow showers will affect a wide area. The snowfall level will drop from approximately 2700 m to 2000 m. During the day the weather will brighten up increasingly from the west and in the south. Thursday will be quite sunny.
The danger of dry avalanches will increase a little on Wednesday. The danger of wet snow avalanches will decrease a little before increasing again on Thursday as the day progresses.

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