Martigny-Verbier

Considerable avalanche danger will be encountered over a wide area

Considerable avalanche danger will be encountered over a wide area

Distinct weak layers exist in the bottom section of the snowpack in particular on steep west, north and east facing slopes. Avalanches can be released easily and reach dangerously large size. Remotely triggered and natural avalanches are possible in isolated cases. Whumpfing sounds and the formation of shooting cracks when stepping on the snowpack can indicate the danger. Avalanches can additionally be released in near-surface layers also. The new snow and wind slabs of the last few days are in some cases prone to triggering. Defensive route selection is advisable. Small to medium-sized gliding avalanches are possible. This applies in the west below approximately 2400 m, and in the east below approximately 2000 m.

The large amounts of new snow and freshly generated snowdrifts in the western and the northern regions from the last few days are settling and consolidating apace. Strong-velocity northerly winds at high altiudes continue to transport the snow masses. Freshly generated snowdrift accumulations are easily triggerable in some places. In the lower part of the snow cover in nearly all regions on west-facing, north-facing and east-facing slopes above approximately 2200 m, weak layers with expansively metamorphosed (faceted) crystals are evident. From central Valais over the Ticino as far as Grisons, as well as generally in places where the snow is shallow, the snowpack layer is most unfavourable. In the western part of Lower Valais and on the northern flank of the Alps the weak old snowpack is frequently overlain with thick layers of fresher snow and the likelihood of the weak ground-level layers triggering is low. As a result of the significant rise in temperatures on Sunday, the snow at low altitudes will become moist, at intermediate and high altitudes it will become moist on the surface.

On the Main Alpine Ridge and northwards therefrom, skies were heavily overcast and there was a small amount of snowfall registered. In the central sector of the southern flank of the Alps it was predominantly sunny. Fresh snow: Between Friday afternoon and Saturday afternoon: - Jura region, northern flank of the Alps: 20 to 30 cm, as much as 50 cm from place to place; - from central Grisons over Goms and the Gotthard region into the Surselva: 10 to 20 cm; - further to the south, less; on the southern flank of the Alps it remained nearly dry. During the two days between Thursday morning and Saturday morning: - western and northern parts of Lower Valais, western sector of the northern flank of the Alps: generally 40 to 70 cm; - Jura region, central and eastern sectors of the northern flank of the Alps: 30 to 50 cm; - from central Valais into Goms, Surselva: 15 to 30 cm; - remaining parts of the Valais as well as northern and central Grisons: less; it remained nearly dry on the southern flank of the Alps. Temperature: At midday at 2000 m, between -8 °C in the northern regions and -5 °C in the southern regions. Wind: Winds were blowing from northerly directions, - predominantly at strong velocity at high altitudes on the northern Alpine Ridge from the Jungfrau region eastwards, and on the Main Alpine Ridge from the Simplon to the Bernina pass; - in the other regions of Switzerland predominantly at light to moderate strength, in the high alpine regions at strong velocity in some places. The precipitation will come to an end on Saturday night, including in the eastern regions. Following a phase of generally clear skies during the night, skies on Sunday morning in western and northern regions will intermittently be heavily overcast. In the eastern regions it will be quite sunny to start with, before cloud cover also moves in there during the course of the afternoon. In the Valais and on the southern flank of the Alps it will be predominantly sunny. Fresh snow: On the northern flank of the Alps as well as in northern and central Grisons, only a few centimetres. Temperature: Temperatures are expected to rise significantly: at midday at 2000 m, to between -1 °C in the western and southern regions and -4 °C in the eastern regions. Wind: - Winds in the Jura region, on the northern Alpine Ridge and on the Main Alpine Ridge will be blowing at strong velocity at high altitudes from northerly directions; - on the southern flank of the Alps, moderate-strength northerly winds will extend down to the upper valleys, subsequently slacken off during the afternoon; - in the other regions of Switzerland, light to moderate winds from northerly to northwesterly directions.

On Monday afternoon in the eastern regions, skies will still be partly cloudy. Later it will become predominantly sunny, as had already taken place in the remaining regions. On Tuesday it will be predominantly sunny in the mountains. On Monday temperatures will rise another notch. On Monday and Tuesday the midday temperature at 2000 m in the western and southern regions will lie at -4 °C, in the eastern regions at -2 °C. Winds will be blowing at light to moderate strength from northerly directions. On Monday the avalanche situation is expected to still remain treacherous to start with. Starting on Tuesday the danger of dry-snow avalanches will incrementally diminish. On Monday and on Tuesday, wet-snow slides and wet-snow avalanches can be expected on steep sunny slopes and, in particular, in sunny rocky terrain. In addition, increasingly frequent gliding avalanches can be expected.