---------------------------------------------------------------- INSTITUTE FOR SNOW AND AVALANCHE RESEARCH DAVOS NATIONAL AVALANCHE BULLETIN NO. 56 for Thursday, 3 January 2008 issue date 2.1.2008, 18:30 hours ---------------------------------------------------------------- AVALANCHE DANGER RISES AMID STRONG SOUTH WINDS ---------------------------------------------------------------- CURRENT CONDITIONS On Wednesday it was predominantly sunny in northern regions. In southern regions it was heavily overcast and a few centimeters of snow fell. The midday temperatures at 2000 m were between minus 4 degrees in western regions, minus 7 degrees in eastern regions and minus 10 degrees in southern regions. Light to moderate southwesterly winds prevailed. The snowfall level in northern and western regions is about 800 m. In southern Upper Valais, northern Ticino and Grisons there is an area wide snowpack above approximately 1200 m. In central and southern Ticino there is snow on north facing slopes above approximately 1800 m; on south facing slopes above approximately 2200 m. Widespread surface hoar has formed on the snow surface. Especially on shady slopes, layers near to the surface are faceted and loosely packed. In northern and western regions there is 10 to 20 cm of loosely packed new snow from last weekend. In areas which have but little snow which occur increasingly in central Grisons, on the southern flank of the Alps and in the Engadine, the snowpack in places is loosely packed down to the ground. SHORT-TERM DEVELOPMENT On Thursday it will be cloudy in northern regions, with bright spots caused by the foehn winds. On the southern flank of the Alps 10 to 20 cm of snowfall is expected by Thursday evening as far down as the low lying areas. On the western Main Alpine Ridge, in the Gotthard region and the Upper Engadine, up to 10 cm of snowfall is expected. At 2000 m, the midday temperatures will be minus 1 degree in northern regions and minus 9 degrees in southern regions. In the valleys subject to foehn winds temperatures will be very mild. The south winds will increase in strength during the morning and blow strongly throughout the day in particular. In southern regions, primarily the new snow will be transported, whereas in northern regions the loosely packed layers of snow near to the surface will tend to be drifted. Snowdrift accumulations prone to triggering will form and increase in mass in the course of the day. AVALANCHE DANGER FORECAST FOR THURSDAY Entire region of the Swiss Alps: Moderate avalanche danger (Level 2) On the Main Alpine Ridge from the Great St. Bernard to the Bernina region and south thereof, the avalanche prone locations are found on slopes with snowdrift accumulations in all aspects above approximately 1800 m, in southern Ticino above approximately 2200 m. Sluffs and small sized avalanches can be triggered particularly on shady slopes by single backcountry skiers and freeriders in places. Prudent route planning is recommended. In the remaining regions on the northern flank of the Alps, in the Valais and Grisons the avalanche prone locations are found primarily on west to north to southeast facing wind loaded slopes as well as in areas adjacent to ridge lines and pass areas in all aspects above approximately 1800 m. The new snowdrift can be triggered even by single persons. It can easily be spotted and should be avoided whenever possible. Through continuing wind transport of snow, the avalanche danger will rise in the course of the day. In western and northern regions in particular, extremely isolated full depth wet snowslides are possible below about 2400 m. This is especially the case in places where the snowpack has opened a glide crack. TREND FOR FRIDAY AND SATURDAY In southern regions it is expected to snow until Saturday. It will snow ongoingly, though only lightly. In northern regions it will be overcast on Friday, despite strong foehn winds. On Saturday it will be variable amid westerly winds. The avalanche danger will continue to increase regionally.