Haut Val de Bagnes

Weakly bonded old snow in the inneralpine regions

Weakly bonded old snow in the inneralpine regions

Distinct weak layers deep in the old snowpack necessitate caution, especially on very steep shady slopes, as well as on south facing slopes above approximately 2800 m. Here avalanches can be triggered in the weakly bonded old snow and reach a dangerous size. These avalanche prone locations are to be found especially in little used terrain and in areas where the snow cover is rather shallow. These places are barely recognisable, even to the trained eye. Whumpfing sounds can indicate the danger. Defensive route selection is required. Maintaining distances between individuals and one-at-a-time descents are recommended, especially on very steep shady slopes.

In the lower part of the snowpack, particularly on west-facing, north-facing and east-facing slopes above approximately 2200 m, weak layers are evident. In the western Lower Valais and on the northern flank of the Alps these ground-level layers are covered over by thick layers of fresher snow so that the likelihood of avalanches being triggered by persons is low. From central Valais over the Ticino as far as Grisons, the snowpack layering is least favourable. In those regions, there have been medium-sized avalanches triggered by persons during the last few days. Gliding avalanches can still trigger on steep grass-covered slopes which have not yet discharged in isolated cases. On shady slopes the upper part of the snow cover is expansively metamorphosed (faceted) and loose in many areas, in some places there is surface hoar blanketing the surface. On steep south-facing slopes a melt-freeze crust forms during the nocturnal hours which is capable of bearing loads.

Following a night of clear skies it was sunny in the mountains during the daytime. Fresh snow: - Temperature: At midday at 2000 m, between +2 °C in the western regions and -1°C in the southern and the eastern regions. Wind: Winds during the nighttime hours were blowing at moderate strength, from place to place at strong velocity, from westerly directions; during the daytime, winds were light. Skies will be partly cloudy during the night, during the daytime it will be quite sunny in spite of cloudbanks. Fresh snow: - Temperature: At midday at 2000 m, between +4 °C in the western regions and +1 °C in the southern and the eastern regions. Wind: Winds will be blowing at moderate strength, in some regions at strong velocity at high altitudes, from westerly directions.

Friday: On Christmas Eve clouds are expected to move in from the west during the morning. In the afternoon, a small amount of precipitation is possible. As a consequence of strong-velocity westerly winds, small but trigger-sensitive snowdrift accumulations will be generated in the northern regions. In the other regions of Switzerland, avalanche danger levels are not expected to change significantly. Saturday: During the night of Christmas Eve a small amount of snowfall is anticipated above approximately 1600 m over widespread areas, in the Bernina region possibly as much as 30 cm. During the daytime on Christmas Day it will become quite sunny in the western regions. As a result of the fresh snow, avalanche danger levels are expected to increase somewhat, in the Bernina regions avalanche danger might increase significantly.