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  INSTITUTE FOR SNOW AND AVALANCHE RESEARCH  DAVOS
               NATIONAL AVALANCHE BULLETIN NO. 131
                for Tuesday, 18 March 2008
             issue date 17.3.2008, 18:30 hours
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  WIDESPREAD CONSIDERABLE AVALANCHE DANGER
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CURRENT CONDITIONS

On Monday it snowed on the northern flank of the Alps and in 
Valais and the northern parts of Grisons. Since Saturday 
morning, 20 to 50 cm of snow has fallen above approximately 2000 
m north of the Rhone and Rhine, in Lower Valais and in 
Praettigau to Samnaun. Towards the south, the amounts of fresh 
snow decreased steadily to about 10 cm. The snowfall level 
dropped from 2000 m to approximately 1200 m. Midday temperatures 
at 2000 m were about minus 3 degrees in the north and about plus 
2 degrees in the south. The westerly wind was moderate, but 
occasionally strong in the west. 
Fresh snow and snow drift accumulations are lying on top of 
older accumulations The bonding of individual near-surface 
layers of the snowpack is still poor in some cases. Below 
approximately 2000 m, the snowpack underneath the fresh snow is 
moist.


SHORT-TERM DEVELOPMENT

On Monday night a little more snow will fall in the north. In 
the east in particular, as much as 10 cm of snow will fall even 
at low altitudes. In the morning the snowfall will ease here as 
well and the weather will be mostly cloudy. The west and south 
will be generally sunny during the day. Midday temperatures at 
2000 m will fall to minus 9 degrees in the north and minus 6 
degrees in the south.


AVALANCHE DANGER FORECAST FOR TUESDAY

Regions north of the Rhone and Rhine excluding the western and 
central Prealps; also Valais; Praettigau; Silvretta; 
Samnaun:
  Considerable avalanche danger (level 3)
Excepting southern Upper Valais, the avalanche prone 
locations are to be found on steep slopes of all aspects 
above approximately 2200 m. Natural avalanches are possible. 
In central Upper Valais, the avalanche prone locations are to 
be found in particular on west to north to south facing wind-
loaded slopes above approximately 2200 m. 
In all areas subject to this danger level, the fresh snow 
drift accumulations and, in some places, the older ones as 
well can be released even by small additional loads. For 
those engaging in backcountry freeriding activities, 
experience in the assessment of avalanche danger is very 
important.

Remaining areas of the Swiss Alps:
  Moderate avalanche danger (level 2)
On the northern flank of the Western and Central Swiss Alps, 
in southern Urseren, in the other regions of northern and 
central Grisons and in the rest of Engadine, the avalanche 
prone locations are to be found primarily on wind-loaded 
slopes of all aspects.  They are above approximately 1800 m 
in the relevant regions of the Prealps and above 
approximately 2200 m elsewhere. On the southern flank of the 
Central and Eastern Swiss Alps, the avalanche prone locations 
are to be found on southwest to north to southeast facing 
wind-loaded slopes above approximately 2200 m. The bonding of 
the fresh snow and relatively small snow drift accumulations 
with the old snowpack remains poor in some places. 
In all areas subject to this danger level, avalanches can be 
triggered – particularly small ones, but up to medium-sized 
in isolated cases.


TREND FOR WEDNESDAY AND THURSDAY

On each of the next two days it will be generally sunny on the 
southern flank of the Swiss Alps. In the remaining regions a 
little snow will fall on both days, and the weather will be 
changeable with low temperatures. The avalanche danger will not 
change significantly.