südliches Urseren

Wind slabs and weakly bonded old snow require caution

Wind slabs and weakly bonded old snow require caution

Faceted weak layers exist in the snowpack. Persons can release avalanches in some places, including medium-sized ones. These avalanche prone locations are barely recognisable, even to the trained eye. Areas where the snow cover is rather shallow are especially precarious. As a consequence of a strong westerly wind, wind slabs will form as well. These are mostly small but in some cases prone to triggering. They are to be avoided in very steep terrain. In particular on very steep grassy slopes small to medium-sized gliding avalanches are possible.

The surface of the snowpack has been influenced by rain, wind and the sun. On the northern flank of the Alps and in Valais, northern Ticino and large parts of Grisons, a crust has formed on the surface up to altitudes of 2600 to 3000 m. In particular north of a line between the Rhone and Rhine, the crust is strong in many cases and partly icy. Above approximately 2600 m, the storm force westerly wind will give rise to small snow drift accumulations that in some instances are prone to triggering. Below this altitude, only the small quantity of fresh snow can be transported. On the northern flank of the Alps, slab avalanches are unlikely to be released in deeper layers. From central Valais through northern Ticino to Grisons, faceted and loosely bonded layers exist in the snowpack. These are lying either directly underneath the rain crust that formed at the end of December, or they are embedded deeper in the snowpack. At elevated altitudes, these weak layers remain prone to triggering in some instances.

The night skies were frequently cloudy in the north and mostly clear in the south. During the day it was party sunny in Ticino and central and southern Grisons, otherwise it was frequently cloudy. In the east, a few snowflakes fell above approximately 1500 m. Fresh snow: - Temperature: At midday at 2000 m: between -1 °C in the north and +3 °C in the south Wind: Moderate to strong from westerly directions, easing a little as the day progressed On Monday night a little snow will fall in the north and Lower Valais above approximately 2000 m. During the day it will be mostly dry and in the north the foehn wind will give rise to some bright spells. The south will be mostly cloudy. Fresh snow: A few centimetres of snow will fall above approximately 2000 m in some areas of the north, Lower Valais and the Gotthard region. Temperature: At midday at 2000 m: between +6 °C in the north and -2 °C in the south Wind: From the southwest - Storm force in the north - Moderate in the south at 2000 m, strong in the high Alpine regions

Wednesday: Snow will fall even at low altitudes. The heaviest snowfall, 20 to 30 cm, will occur on the northern flank of the Alps and in Lower Valais and Grisons. In the afternoon the snowfall will cease in the west. The wind will veer to northwesterly and become strong at elevated altitudes and in the south. Ticino will become increasingly sunny as the day progresses. It will become significantly colder. The avalanche danger will increase over a wide area as a consequence of fresh snow. Thursday: In the north and east a little more snow will fall, even at low altitudes. In southern Valais there will be prolonged bright spells; Ticino will be quite sunny. As the day progresses, the northerly wind will ease gradually from the west. It will remain cold. The avalanche danger will not change significantly.