National avalanche bulletin

for Tuesday, 9 February 2010

issue date 8.2.2010, 18:30 hours

Widespread considerable avalanche danger decreasing only slowly

Current conditions

Monday was sunny. Midday temperatures at 2000 m were about minus 3 degrees in the north and minus 6 degrees in the south. The southerly wind was light to moderate.
Solar radiation has improved the bonding of the snowpack a little on south facing slopes. The bonding of the snowpack is most favourable in the central and eastern parts of the main Alpine ridge and in the south. In the other regions, the bonding of the snowpack is unfavourable in many places. In particular in areas close to the tree line and places that are generally sheltered from the wind, the bottom and middle layers of the snowpack are highly faceted. Avalanches can be released easily in places where the top layer of the snowpack consists of snow drift accumulations. The bonding of the snowpack improves a little with altitude because of the wind's greater influence.

Short-term development

On Monday night the skies will be clear. Tuesday morning will remain partly sunny. During the day, cloud will build up from the west. In the afternoon, light snow will begin to fall in the west. Midday temperatures at 2000 m will be about minus 5 degrees in the north and minus 8 degrees in the south. The wind will be light and become westerly to northwesterly.

Avalanche danger forecast for Tuesday

Northern flank of the Alps; Valais; northern Ticino; Grisons excluding Val Calanca and Val Moesa:

Considerable avalanche danger (level 3)

Avalanche prone locations are to be found, in particular, on west to north to southeast facing steep slopes. They are to be found above approximately 1800 m on the northern flank of the Alps excluding Urseren and in northern Grisons, and above approximately 2000 m in the other regions subject to this danger level. The most treacherous places are those where relatively old snow drift accumulations are lying on a weakly bonded old snowpack. These snow drift accumulations are covered by loosely bonded snow in some cases and therefore difficult to recognise. Avalanches can be triggered by a single person. Those engaging in backcountry touring and off-piste activities must dispose of experience in the assessment of avalanche danger. On highly frequented slopes in the ski resorts, the avalanche situation is more favourable.

Central Ticino; Sotto Ceneri; Val Calanca; Val Moesa:

Moderate avalanche danger (level 2)

The avalanche prone locations are to be found on southwest to north to southeast facing steep slopes above approximately 1600 m. Older snow drift accumulations call for careful route selection.

Trend for Wednesday and Thursday

Wednesday and Thursday will be mostly cloudy, and some snow will fall in the north. It will be very cold. The avalanche situation will not change significantly.

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