National avalanche bulletin

for Friday, 12 March 2010

issue date 11.3.2010, 18:30 hours

Caution urged towards snowdrift and regionally poor snow layering

Current conditions

On Thursday in the Valais, in northern Ticino and in Grisons, it was partly sunny, elsewhere it was heavily overcast in general. On Wednesday night in southern regions there was an additional few centimeters of snowfall. During the day on Thursday, there was light snowfall in northeastern regions in particular. The midday temperatures at 2000 m were minus 9 degrees in northern regions and minus 7 degrees in southern regions. A light to moderate westerly to northerly wind was blowing.
The snowpack is highly varied even across small surface areas. Snowdrift accumulations have often been deposited on the surface. In wind protected areas of northern regions in particular, these snowdrift accumulations are covered and concealed by loosely packed snow. Summits and ridges have been windblown and are free of snow in some regions. In the intermediate and lowermost layers, the snowpack is faceted and loosely packed widespread. This is especially the case in the inneralpine regions and in some sectors of the central and western parts of the northern flank of the Alps. Fractures in the old snowpack now occur less often, but are still possible. The snow layering in the eastern part of the northern flank of the Alps, on the southern flank of the Alps and on heavily frequented routes is somewhat more favourable.

Short-term development

On Friday it is expected to be increasingly sunny. The midday temperatures at 2000 m will be minus 8 degrees in northern regions and minus 5 degrees in southern regions. A light to moderate northeasterly to northerly wind will be blowing.

Avalanche danger forecast for Friday

Lower Engadine south of the Inn River; Münstertal:

Considerable avalanche danger (Level 3)

The avalanche prone locations are to be found primarily on wind loaded slopes in southwestern to northern to eastern expositions above approximately 2000 m. The major peril stems from snowdrift accumulations. These can be triggered even by a single backcountry skier or freerider. In isolated cases, avalanches can break through to the old snowpack. Backcountry tours necessitate extensive experience in spotting and evaluating avalanche hazards as well as a cautious route selection.

Northern flank of the Alps; Valais; Ticino; northern and central Grisons; Lower Engadine north of the Inn River; Upper Engadine; Val Calanca; Val Moesa; Bergell; Puschlav:

Moderate avalanche danger (Level 2)

In the northern Prealps, the avalanche prone locations are to be found primarily on wind loaded slopes in all expositions above approximately 1600 m. On the northern flank of the Alps not including the Prealps, in the Valais not including the southern Simplon region, in northern and central Grisons, in the Upper Engadine and in the Lower Engadine north of the Inn River, the avalanche prone locations are to be found primarily on steep, southwest to north to southeast facing slopes above approximately 1800 m. Snowdrift accumulations can be triggered by large additional loading in particular. Apart from that, avalanches can fracture in the old snowpack in isolated cases, especially in transition areas from shallow to deep snow and in general at altitudes between 2000 and 3000 m.
On the southern flank of the Alps not including the Münstertal, the avalanche prone locations are to be found on steep slopes in all expositions above approximately 1800 m. New fallen snow and freshly formed snowdrift are poorly bonded with the old snow in some places.
In all regions of this danger level, the snow situation, which is highly varied even over small surface areas, makes a cautious route selection imperative.

Trend for Saturday and Sunday

Over the weekend it will be quite sunny in western and southern regions. In eastern regions it will be partially overcast. The avalanche danger is not expected to change significantly.

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