Considerable danger of wet avalanches will be encountered over a wide area
Edition: 29.4.2021, 17:00 / Next update: 30.4.2021, 18:00
Snowpack
New snow is being deposited atop a dry old-snowpack surface in high alpine regions in particular, thereby blanketing the fresh snow which fell on Thursday in the western and the southern regions. In particular during the course of the daytime at high altitudes, snowdrift accumulations, which to some extent are prone to triggering, will be generated.
As a result of cloud cover and precipitation, the moist snowpack surface below approximately 2400 m is hardly able to re-gain firmness during the nocturnal hours.
The snow cover is throughly wet below approximately 3000 m on south-facing slopes, below approximately 2800 m on east-facing and west-facing slopes. On north-facing slopes the process of snowpack moistening between 2200 and 2400 m is continuing apace. On steep north-facing slopes above approximately 2800 m, there is still loosely-packed snow evident in places.
Observed weather on Thursday, 29.04.2021
Skies were heavily overcast for the most part. Precipitation was registered on the northern flank of the Alps more than anywhere else, in the Lower Valais and in the central sector of the southern flank of the Alps the snowfall level lay at 2000 m.
Fresh snow
Above approximately 2400 m:
  • furthermost western part of Lower Valais and Bedretto valley: 15 to 30 cm;
  • remaining parts of Lower Valais, northern Upper Valais as well as remaining parts of northern Ticino and Main Alpine Ridge from Rheinwald into the Bernina region: 5 to 15 cm;
  • in other regions of Switzerland, less; or else, it remained dry.
Temperature
At midday at 2000 m, at +2 °C.
Wind
Winds were blowing at light to moderate strength from southerly directions.
Weather forecast through Friday, 30.04.2021
Following the termination of the period of precipitation on Thursday night, skies in the northern regions are predominantly overcast, accompanied by bright intervals in the inneralpine and eastern regions. Already during the morning hours, precipitation sets in anew from the west. In the southern regions skies are heavily overcast and repeated bouts of precipitation are predicted.
Fresh snow
The snowfall level in the northern regions lies between 1800 and 2200 m; in the southern regions between 2000 and 2400 m. Between Thursday afternoon and Friday afternoon:
  • furthermost western part of Lower Valais and Main Alpine Ridge from Lukmanier Pass to Bernina Pass: 15 to 30 cm;
  • in the other regions of Switzerland, mostly 5 to 15 cm.
Temperature
At midday at 2000 m, between +3 °C in the western and the southern regions and +5 °C in the eastern regions.
Wind
Winds will be blowing from southwesterly directions. At high altitudes:
  • at light to moderate strength during the nighttime hours;
  • at moderate to strong velocity during the daytime hours.
Outlook through Sunday, 02.05.2021
Saturday
Skies will be heavily overcast for the most part, and repeated rounds of precipitation are anticipated. Most of the precipitation will fall in the central sector of the southern flank of the Alps, presumably 20 to 40 cm, and the snowfall level at approximately 2200 m. In the northern regions the snowfall level will lie somewhat lower down. The danger of dry-snow avalanches is expected to increase over widespread areas at high altitudes. Wet-snow and gliding avalanches continue to be expected.
Sunday
The focal point of the precipitation on Saturday night will be in the southern regions. Subsequently, it will come to and end there, and as a result of northerly winds bright intervals are anticipated. In the northern regions, snowfall will continue during the daytime hours, and the snowfall level will rapidly descend to approximately 1000 m. The amounts of expected precipitation are as yet uncertain. Above 2200 m, it is presumed that about 15-30 cm of fresh snow will be registered over widespread areas, in the eastern and the southern regions somewhat more from place to place. The danger of dry-snow avalanches will increase particularly at heightened altitudes over widespread areas. Wet-snow and gliding avalanches continue to be expected.