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      WSL Institute for Snow and Avalanche Research SLF
               NATIONAL AVALANCHE BULLETIN NO. 39
                for Tuesday, 3 January 2012
             issue date 2.1.2012, 18:30 hours
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  WIDESPREAD CONSIDERABLE AVALANCHE DANGER
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CURRENT CONDITIONS

On Sunday night the skies were clear at times. Only in the east was it still sunny at times during 
the day. Elsewhere, precipitation arrived from the west. The snowfall level dropped from 1800 m to 
approximately 1000 m. 10 to 15 cm of snow fell in the western part of the northern flank of the Alps, 
western Lower Valais and Ticino, but only a few centimetres fell elsewhere. The southwesterly wind 
was moderate, but strong at times. The conditions gave rise to fresh snow drift accumulations that 
are prone to triggering. The midday temperature at 2000 m was about minus 1 degree.

The large quantities of fresh snow that fell in the final week of the old year have settled to a 
large extent. Nonetheless, the various layers of the fresh snow and snow drift accumulations have 
not yet bonded sufficiently well in some cases. On the main Alpine ridge and in Engadine in 
particular, the near-ground layers of the snowpack are faceted and prone to triggering on north 
facing slopes above approximately 2500 m.


SHORT-TERM DEVELOPMENT

On Monday night, 10 to 20 cm of snow will fall on the northern flank of the Alps from the eastern 
Bernese Oberland to Liechtenstein, and in northern Grisons, but less will fall elsewhere. During 
the day, the weather will become increasingly sunny in the east. It will be fairly sunny elsewhere. 
The midday temperature at 2000 m will be about minus 2 degrees. The westerly wind will be moderate 
to strong.

The fresh snow drift accumulations in particular remain prone to triggering.


AVALANCHE DANGER FORECAST FOR TUESDAY

Northern flank of the Alps excluding the prealps; Valais; northern Ticino; Grisons excluding 
Lower Val Calanca and Lower Val Moesa:
  Considerable avalanche danger (level 3)
  
The avalanche prone locations are to be found, in particular, on wind-loaded slopes of all aspects. 
They are to be found above approximately 2000 m in the relevant regions on the northern flank of the 
Alps, and above approximately 2200 m in the other regions subject to this danger level. Both fresh 
and older snow drift accumulations can be released easily in some places. In addition, on the main 
Alpine ridge and in Upper Engadine in particular, avalanches can be released in deep layers of the 
snowpack on north facing slopes above approximately 2500 m. For those venturing off piste, caution 
and experience in the assessment of avalanche danger are important.

Prealps; central Ticino; Lower Val Calanca; Lower Val Moesa:
  Moderate avalanche danger (level 2)
  
The avalanche prone locations are to be found, in particular, on wind-loaded slopes of all aspects 
above approximately 1800 m. Fresh snow drift accumulations, but also older accumulations in some 
cases, are prone to triggering, but mostly small. They must be evaluated with care and prudence.

On the northern flank of the Alps and in Valais, the Gotthard region, northern and central Grisons, 
and Lower Engadine, in particular, full-depth avalanches can occur on steep grassy slopes and on 
road embankments in all aspects below approximately 2000 m. Exposed parts of transportation routes 
can be endangered in isolated cases.


TREND FOR WEDNESDAY AND THURSDAY

On Tuesday night a little snow will fall in the north. During the day, the weather will become 
increasingly dry. Snow will begin to fall again on Thursday. On each of the next two days, the wind 
will be strong to very strong from the west to northwest. The strong wind will give rise to a 
greater prevalence of avalanche prone locations on Wednesday and Thursday.