nördliches Urseren

Considerable avalanche danger will be encountered over a wide area

Considerable avalanche danger will be encountered over a wide area

As a consequence of a strong wind from northerly directions, sometimes large wind slabs formed. Single winter sport participants can release avalanches easily. Avalanches can in some places be released in the weakly bonded old snow also, especially in areas where the snow cover is rather shallow. They can reach large size. Whumpfing sounds and the formation of shooting cracks when stepping on the snowpack can indicate the danger. Backcountry touring and other off-piste activities call for experience in the assessment of avalanche danger. In particular on very steep sunny slopes moist snow slides and avalanches are possible.

The fresh snow and snowdrifts of the last week are gradually settling and consolidating. As a result of strong-velocity northerly winds on the weekend, a great deal of snow was transported at high altitudes. The freshly generated snowdrift accumulations are easily triggerable in some places. In the lower part of the snowpack in nearly all regions, there are weak layers containing expansively metamorphosed (faceted) crystals on west-facing, north-facing and east-facing slopes above approximately 2200 m. From central Valais over the Ticino as far as Grisons, as well as in general in places where the snow is shallow, the snowpack layering is least favourable. In the western Lower Valais and on the northern flank of the Alps the weak old snow, which in many places is 100 to 200 cm deep since the beginning of December, is covered by fresher layers of snowfall. In these places the likelihood of triggering is low in these ground-level layers. As a result of temperatures rising further and daytime solar radiation, the snow at lower and intermediate altitudes is becoming moist, at higher altitudes superficially moist.

On Saturday night in the northern and the eastern regions there was an additional amount of fresh snow registered which fell down to low lying areas. After skies cleared up during the latter part of the night, in the western and the northern regions skies became increasingly overcast during the morning hours, in the eastern regions it remained still sunny to start with. During the afternoon cloud cover moved in, including into the eastern regions. In the Valais it was partly sunny, in the southern regions predominantly so. Fresh snow: Between Saturday afternoon and Sunday morning: - Jura region, northern flank of the Alps, northern and central Grisons: 5 to 15 cm from place to place; - in the other regions of Switzerland, only a few centimetres; in the southern Valais and on the southern flank of the Alps it remained dry. Thus, in the three days between Thursday morning and Sunday morning: - western and northern parts of Lower Valais, western regions in the western sector of the northern flank of the Alps: 50 to 80 cm; - remaining parts of the northern flank of the Alps: 30 to 50 cm; - from central Valais into Goms, as well as in northern and central Grisons: 15 to 30 cm; - remaining parts of the Valais and the Gotthard region, southern Grisons: 5 to 15 cm; on the southern flank of the Alps it remained predominantly dry. Temperature: At midday at 2000 m, between -2 °C in the western regions and -5 °C in the eastern regions, as well as +2 °C in the southern regions. Wind: Winds were blowing from northerly directions, - at moderate to strong velocity in the Jura region during the nighttime hours on Saturday, mostly at light strength during the daytime on Sunday; - at moderate to strong velocity, intermittently at storm-strength, on the northern Alpine Ridge and on the Main Alpine Ridge; - winds on the southern flank of the Alps and in the Engadine were blowing at moderate to strong velocity during the nocturnal hours, during the daytime slackening off; - in the remaining regions of the Valais, of the northern flank of the Alps and of Grisons, winds were blowing at light to moderate strength. On Sunday night in the eastern regions, a small amount of precipitation is anticipated. The snowfall level will ascend to 1600 to 1800 m. In the western and the southern regions, nighttime skies will be predominantly clear. In the early morning hours on Monday in the central and eastern sectors of the northern flank of the Alps and from northern Grisons over the Silvretta as far as Samnaun, there will be residual cloudbanks which will subsequently disperse during the course of the morning. In the other regions of Switzerland it will be predominantly sunny and significantly milder. Fresh snow: Liechtenstein, Prättigau, Silvretta, Samnaun: as much as 5 cm above approximately 2000 m. Temperature: Temperatures will rise, at midday at 2000 m to between +5 °C in the western and southern regions, and +2 °C in the furthermost eastern regions. Wind: In the central and eastern sectors of the Main Alpine Ridge, moderate to strong-velocity winds will persist on Sunday evening, subsequently slacken off during the night; elsewhere, winds will be blowing generally at light to moderate strength from northerly directions.

On Tuesday it will be quite sunny in the mountains, accompanied by cloudbanks; on Wednesday predominantly sunny. It will continue to be mild. On Wednesday the zero-degree level will lie between 2800 m in the western and southern regions and 2500 m in the eastern regions. On Wednesday the zero-degree level is expected to ascend to over 3000 m during the course of the day. The danger of dry-snow avalanches will incrementally decrease, particularly in the regions of the west and the north where snowfall has been heaviest. The danger of moist-snow avalanches will increase during the course of each day. In addition, gliding avalanches continue to be expected. These releases can grow to large size in the regions where snowfall has been heaviest.