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      WSL Institute for Snow and Avalanche Research SLF
               NATIONAL AVALANCHE BULLETIN NO. 122
                for Thursday, 10 March 2011
             issue date 9.3.2011, 18:30 hours
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  PREDOMINANTLY FAVOURABLE AVALANCHE SITUATION, WITH TREACHEROUS SPOTS IN UNFREQUENTED TERRAIN
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CURRENT CONDITIONS

On Wednesday it was sunny in the Swiss Alps. The midday temperatures at 2000 m were between minus 2 
and plus 2 degrees. The wind was blowing at light to moderate velocity from northwesterly directions.

Poorly consolidated intermediate layers are often interspersed inside the snowpack. At altitudes 
above the treeline, such layers are more widespread than at still higher altitudes which have been 
under heavy wind influence. The snowpack displays an increasingly reduced tendency toward fracture 
propagation. In the region from the central part of the southern flank of the Alps into the 
Upper Engadine, the snow layering is more favourable. During the morning hours, steep south facing 
slopes are capable of bearing loads up towards 3000 m in many places.

SHORT-TERM DEVELOPMENT

On Wednesday night, the skies will be generally clear. During the day on Thursday, it will be 
predominantly sunny. The midday temperatures at 2000 m will be between zero degrees and 
minus 3 degrees. The wind will be blowing from westerly to northwesterly directions. In the 
furthermost northern regions and in high alpine regions, it will blow at moderate to strong 
velocity, elsewhere at light to moderate strength widespread. Small sized snowdrift accumulations 
can form from place to place.

AVALANCHE DANGER FORECAST FOR THURSDAY

Simplon region; Binntal:
  Considerable avalanche danger (Level 3)
  
The avalanche prone locations are to be found primarily on steep slopes of western to northern to 
eastern exposition above approximately 2000 m. Avalanches can be triggered even by a single 
backcountry skier or freerider. Seldom frequented slopes should be evaluated with particularly 
great care.

Northern flank of the Alps; Valais not including Simplon region and not including Binntal; Ticino; 
Grisons:
  Moderate avalanche danger (Level 2)
  
The avalanche prone locations are to be found primarily on steep slopes of northwestern to northern 
to eastern exposition. On the northern flank of the Alps not including Urseren, they occur above 
approximately 1800 m, elsewhere above approximately 2200 m. Older and generally thin snowdrift 
accumulations, more than anything else, should be assessed with great care. Particularly in those 
places where they have been deposited on top of weak, coarse grained layers of old snow, even a 
single person can trigger avalanches which then can sweep along more large scaled surface areas in 
some places. The hazardous zones are not widespread, however. The peril, in general, is more 
pronounced in seldom frequented terrain than in the remaining regions. A prudent route selection 
is important.

In all regions of the Swiss Alps, moist sluffs and, in isolated cases, avalanches can be expected 
over the course of the day on sunny slopes below approximately 2500 m.


TREND FOR FRIDAY AND SATURDAY

On Friday it is expected to be predominantly sunny. On Saturday in southern regions, light snowfall 
is anticipated. In northern regions, foehn wind conditions will arise. The avalanche danger may 
escalate somewhat on Saturday in southern regions, due to the snowfall; and in northern regions, 
due to the foehn wind and daytime warmth.