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      WSL Institute for Snow and Avalanche Research SLF
               NATIONAL AVALANCHE BULLETIN NO. 63
                for Friday, 27 January 2012
             issue date 26.1.2012, 18:30 hours
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  CAUTION URGED TOWARDS FULL DEPTH SNOWSLIDES
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CURRENT CONDITIONS

On Thursday in the furthermost northeastern regions it was still overcast, elsewhere generally sunny. 
The midday temperatures at 2000 m were minus 1 degree in northern and minus 5 degrees in southern 
regions. The wind was blowing at light to moderate velocity from the northwest.

The snowpack is favourably structured by and large, evidencing hardly any trigger sensitive layers. 
Particularly on the Main Alpine Ridge on north facing slopes above approximately 2500 m, the snowpack 
layers which are near the ground are weakly bonded. The deep snowpack tends to insulate the ground, 
prompting the activity of full depth snowslides below about 2400 m to continue.

SHORT-TERM DEVELOPMENT

On Friday it will be heavily overcast and in northern regions a few centimeters of snowfall is 
expected. The midday temperature at 2000 m will be minus 4 degrees. A light wind will be blowing.


AVALANCHE DANGER FORECAST FOR FRIDAY

Entire region of the Swiss Alps excluding Sotto Ceneri:
  Moderate danger of dry avalanches (Level 2)
  
On the northern flank of the Alps, the avalanche prone locations are to be found on steep slopes in 
all aspects above approximately 1800 m. In the Valais, in northern Ticino, in northern and central 
Grisons, in the Engadine and in the Muenstertal, the danger zones are found on steep slopes in all 
aspects above approximately 2000 m. In central Ticino, in Val Calanca, in Val Moesa, in Bergell and 
in Puschlav, the avalanche prone locations are to be found primarily on steep, southwest to north to 
southeast facing slopes above approximately 2000 m.

Avalanches can be triggered primarily through large additional loading. Particularly layers of 
snowdrift near the uppermost surface of the snowpack should be assessed with great care.

On the northern flank of the Alps, in the Valais, in northern Ticino, in northern and central 
Grisons, in the Engadine and in the Muenstertal, there is moderate danger of full depth snowslides. 
Below about 2400 m, full depth snowslides of medium size are possible at any and all times. This is 
particularly the case on steep, grassy slopes in eastern, southern and western aspects. Exposed 
sections of transportation routes are endangered in isolated cases. Caution is urged below glide 
cracks.

In central Ticino, in Val Calanca, in Val Moesa, in Bergell and in Puschlav, the danger of full depth 
snowslides is low.

TREND FOR SATURDAY AND SUNDAY

Over the weekend, skies will be predominantly overcast. It will be cold and some snowfall is 
anticipated. The avalanche danger is not expected to change significantly.