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      WSL Institute for Snow and Avalanche Research SLF
               NATIONAL AVALANCHE BULLETIN NO. 80
                for Monday, 1 February 2010
             issue date 31.1.2010, 18:30 hours
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  AVALANCHE DANGER IS CONSIDERABLE WIDELY SPREAD
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CURRENT CONDITIONS

On Sunday in the western and northern regions, it was variably cloudy. In the eastern regions it 
was intermittently sunny, in the southern regions predominantly so. Between Saturday and Sunday 
afternoon in the Jura and in the Prealps there was 10 to 20 cm of snowfall, in eastern regions 
locally as much as 30 cm. Since Thursday on the northern flank of the Alps not including Urseren, 
there has been 50 to 80 cm of new fallen snow, in eastern regions as much as 110 cm. In the Jura, 
in the Valais, in the Gotthard region, in the northern Surselva and in northern Grisons there has 
been 20 to 50 cm of snowfall, in the remaining regions of central Grisons and of northern Ticino, 
as well as in northern Engadine, there has been 10 to 20 cm of snow. On Sunday the midday temperature 
at 2000 m was minus 15 degrees. A light to moderate northerly wind was blowing.

The fresh-fallen snow is settling and consolidating only slowly, even at intermediate altitudes. In 
northern regions, the uppermost layer of new snow is generally loosely packed. It covers over layers 
of snowdrift from the last few days which are prone to triggering. In addition, the old snowpack is 
inadequately consolidated widespread. In the central part of the southern flank of the Alps the snow 
layering is more favourable.

SHORT-TERM DEVELOPMENT

On Monday in southern regions it is expected to be generally sunny, in northern regions temporarily 
so. During the afternoon on the northern flank of the Alps, 5 to 10 cm of snowfall is anticipated. 
The midday temperature at 2000 m will be minus 12 degrees. A moderate westerly to northwesterly wind 
will be blowing. In the afternoon, the wind will be strong at high altitudes and will transport the 
loosely packed snow from the uppermost layers of the snowpack.

AVALANCHE DANGER FORECAST FOR MONDAY

Northern flank of the Alps; Jura; Valais; Gotthard region; regions of central Grisons in the central 
part of Main Alpine Ridge; northern Surselva; Flims- Untervaz:

  Considerable avalanche danger (Level 3)
  
On the northern flank of the Alps not including Urseren, the avalanche prone locations are to be 
found on steep slopes in all expositions above approximately 1600 m. In the remaining regions of 
this danger level, the avalanche prone locations are to be found primarily on wind loaded slopes in 
all expositions. In the Jura they are above approximately 1400 m. In the northern Valais, in Goms, 
in the central part of the Main Alpine Ridge not including upper Val Calanca and upper Val Moesa, as 
well as in northern Surselva and in Flims-Untervaz, they are found above approximately 1800 m. In 
the remaining southern Valais, they are above approximately 2200 m.

In all regions of this danger level, a single backcountry skier or freerider can trigger avalanches 
which might also fracture and sweep along more deeply embedded layers of the snowpack. Extensive 
experience in spotting and assessing avalanche perils is imperative for backcountry skiing and 
freeriding tours.

Remaining regions of Grisons; Ticino not including Main Alpine Ridge:

  Moderate avalanche danger (Level 2)
  
The avalanche prone locations are to be found primarily on wind loaded slopes in all expositions. In 
Praettigau they are found above approximately 1800 m, elsewhere above approximately 2000 m. The 
freshly formed and somewhat older snowdrift accumulations are prone to triggering. The snow masses 
which are released are generally of small size. A cautious route selection should be exercised in 
order to avoid snowdrift whenever possible.

TREND FOR TUESDAY AND WEDNESDAY

On Monday night along the northern flank of the Alps, a bit of snowfall is expected. On Tuesday it 
will be predominantly sunny. On Wednesday in northern regions, there will be snowfall. In the 
furthermost southern regions it will be sunny. The avalanche danger will subside to begin with, then 
increase again somewhat from region to region on Wednesday.