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  INSTITUTE FOR SNOW AND AVALANCHE RESEARCH  DAVOS
               NATIONAL AVALANCHE BULLETIN NO. 176
                for Friday, 2 May 2008
             issue date 1.5.2008, 18:30 hours
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  GENERALLY FAVOURABLE AVALANCHE SITUATION DURING THE MORNING 
HOURS
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CURRENT CONDITIONS

On Wednesday night it was partly clear in western regions. In 
eastern and southern regions there was more snowfall. During the 
day on Thursday it was predominantly sunny in western and 
southern regions, variably cloudy in eastern regions. Since 
Tuesday evening, there have been the following amounts of new 
snow: central part of the southern flank of the Alps, 30 to 40 
cm; central part of Main Alpine Ridge and Upper Engadine, 20 to 
30 cm; remaining regions, widespread 10 to 20 cm; western part 
of the northern flank of the Alps and Lower Engadine, less than 
10 cm. The midday temperatures at 2000 m were minus 2 degrees in 
northern regions, plus 1 degree in southern regions. Light winds 
prevailed. 
In zones above approximately 2600 m, the snowpack on north 
facing slopes is still wintery dry. In the inneralpine regions 
of the Valais and Grisons, the snowpack fundament is weak 
widespread. On south facing slopes below about 2800 m, on north 
facing slopes below about 2400 m, the snowpack is soft, 
thoroughly wet and prone to triggering. It can stabilise during 
the night through the freezing of its uppermost layers.


SHORT-TERM DEVELOPMENT

On Thursday night it will be predominantly clear. In 
northeastern regions it will remain partly overcast until 
morning. Elsewhere it will be mostly sunny during the day on 
Friday, apart from high altitude cloudbanks. In the course of 
the day, cumulonimbus clouds will form. In general, light to 
moderate westerly to northwesterly winds will prevail, at 
altitudes over 3000 m the winds will be strong in places. The 
midday temperature at 2000 m will be plus 2 degrees. 
Through the daytime warming cycle and solar radiation, the 
snowpack surface crust will soften noticeably and forfeit its 
firmness.


AVALANCHE DANGER FORECAST FOR FRIDAY

Entire region of the Swiss Alps:
  Moderate danger of dry avalanches (Level 2)
The avalanche prone locations are to be found on northwest to 
north to northeast facing steep slopes above approximately 
2600 m in particular. Especially snowdrift accumulations 
which were formed recently can be triggered as slab 
avalanches. Particularly in this terrain, cautious route 
selection is recommended.

The danger of wet snow avalanches is subject to a marked daytime 
cycle. Through the thawing of the melt-freeze crust, which is 
capable of bearing loads, the danger level will rapidly rise to 
"considerable" (Level 3). Below about 2600 m, wet snow 
avalanches can be expected in all aspects. Isolated large sized 
wet snow avalanches which can fracture the entire snowpack down 
to the ground are also possible. This is particularly the case 
in the inneralpine regions of the Valais and Grisons. 
Backcountry touring and ascents to huts should be completed 
sufficiently early.


TREND FOR SATURDAY AND SUNDAY

Both days will be quite sunny and mild. The nights will be 
generally clear with good outgoing radiation. The danger of dry 
avalanches will subside. Favourable backcountry touring 
conditions will prevail in the morning hours. The danger level 
of wet snow avalanches will be subject to a marked daytime 
cycle.