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  INSTITUTE FOR SNOW AND AVALANCHE RESEARCH  DAVOS
               NATIONAL AVALANCHE BULLETIN NO. 68
                for Tuesday, 15 January 2008
             issue date 14.1.2008, 18:30 hours
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  CONSIDERABLE AVALANCHE DANGER
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CURRENT CONDITIONS

In the northeast and Valais on Monday, the foehn wind gave rise 
to some bright spells. Otherwise, it was an overcast day. A few 
centimetres of snow fell in the south. The midday temperature at 
2000 m was about minus 2 degrees in the north and minus 4 
degrees in the south. The southerly wind was moderate, but 
strong at times in the valleys exposed to the foehn. The 
conditions gave rise to fresh snow drift accumulations that are 
prone to triggering. 
The fresh snow from Saturday is slowly bonding. In Valais, 
Ticino and Grisons, it is lying on a weakly bonded old snowpack. 
On the northern flank of the Alps, the bonding of the old 
snowpack is better. Here, the more recent snow drift 
accumulations in particular are treacherous.


SHORT-TERM DEVELOPMENT

On Monday night a weak weather disturbance will cross 
Switzerland. During the day the weather will be rather pleasant 
in the north, with the foehn wind giving rise to some bright 
spells. In Ticino it will be overcast, and 10 to 15 cm of snow 
will fall. In the west and Valais, 5 to 10 cm of snow will fall. 
The midday temperature at 2000 m will be about minus 1 degree in 
the north and about minus 5 degrees in the south. The wind will 
be moderate to strong from the southwest. 
The conditions will give rise to fresh snow drift accumulations 
that are prone to triggering. This applies in particular to the 
areas that are exposed to the foehn wind.


AVALANCHE DANGER FORECAST FOR TUESDAY

Entire region of the Swiss Alps:
  Considerable avalanche danger (level 3)
On the main Alpine ridge from the Matterhorn to the Bernina 
Pass and to the south, avalanche prone locations are to be 
found on steep slopes of all aspects above approximately 1600 
m. In the rest of Valais and the rest of Grisons, avalanche 
prone locations are to be found on steep slopes of all 
aspects above approximately 1800 m. On the northern flank of 
the Alps excluding the Gotthard region, avalanche prone 
locations are to be found, in particular, on southwest to 
north to southeast facing wind-loaded slopes above 
approximately 1800 m. 
In all regions, fresh snow drift accumulations can be 
released by a single person and are to be avoided as far as 
possible. Avalanches are likely to be released in the old 
snowpack, in particular in central Valais, southern Upper 
Valais, central Grisons and Engadine. On the southern flank 
of the Central Swiss Alps, where the fresh layer of the 
snowpack is deeper and gradually becoming more stable, areas 
with a shallow snowpack and transitions from a shallow to a 
deep snowpack in particular must be critically assessed.  
Experience in the assessment of avalanche danger is required.


TREND FOR WEDNESDAY AND THURSDAY

On Tuesday night a foehn storm will occur. On Wednesday snow 
will fall in the south. In the north it will be mostly dry. 
Thursday will be changeable with some bright spells. On 
Wednesday the avalanche danger will increase slightly in the 
south. In the north, the foehn wind will cause the treacherous 
conditions to persist.