Zervreila

Wet avalanches during the day

Wet avalanches during the day

Dry avalanches can in isolated cases be released in near-surface layers. The mostly small wind slabs of the last few days are to be evaluated with care and prudence in terrain where there is a danger of falling. Faceted weak layers exist deep in the snowpack. In very isolated cases avalanches can also be released in near-ground layers and reach medium size. This applies especially on extreme north and east facing slopes above approximately 2200 m in little used terrain. These avalanche prone locations are very rare but are barely recognisable, even to the trained eye. Extremely slopes are to be traversed by snow sport participants one at a time. The surface of the snowpack cooled hardly at all during the overcast night. Already in the early morning individual wet and gliding avalanches are possible. As a consequence of warming during the day and solar radiation medium-sized wet avalanches are possible, especially on very steep sunny slopes below approximately 2600 m, as well as on very steep north facing slopes below approximately 2200 m. Backcountry tours should be concluded timely. On steep grassy slopes gliding avalanches are possible. Areas with glide cracks are to be avoided.

The snowpack surface is brown-coloured over widespread areas as a result of Sahara dust. This reduces the amount of solar radiation which gets reflected, which in turn heightens the warmth which is drawn into the snowpack. In spite of reduced solar radiation the snowpack on south-facing slopes below approximately 2400 m, and on east-facing and west-facing slopes below approximately 2100 m, is thoroughly wet. Particularly in the regions of the north where snowfall has been heaviest, numerous glide cracks have opened. Snowdrift accumulations which have been generated over the last few days were deposited on north-facing slopes atop expansively metamorphosed (faceted) old snow but are still prone to triggering only in isolated cases. More deeply embedded inside the snowpack, particularly in the southern Valais and in the inneralpine and southern regions of Grisons, there are pronounced weak layers evident. However, since the end of February no fractures of dry-snow avalanches have been recorded as triggering in these layers. As a consequence of the increased moistening of the snowpack, fractures in these weak layers have become possible once again.

Following a night of partly cloudy skies with reduced longwave outgoing radiation, it was very hazy during the daytime hours due to high-altitude cloudbanks and a great deal of Sahara dust in the atmosphere. Fresh snow: - Temperature: At midday at 2000 m, between +5 °C in the northern regions and +1 °C in the southern regions. Wind: Winds were blowing predominantly at light strength from easterly directions. Nighttime skies will be predominantly overcast and the outgoing longwave radiation significantly reduced. Above approximately 2200 m a small bit of snowfall is possible. In the northern regions the cloudiness will recede somewhat from the west during the daytime hours, but it will still remain hazy as a result of the Sahara dust. In the southern regions skies will remain overcast, but dry for the most part. 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: - In the Jura region and the Prealps, a bise wind will be blowing at moderate to strong velocity; - in the other regions of Switzerland, a light to moderate strength easterly wind will be blowing.

Saturday: In the northern regions the bise wind will slacken off during the night and skies will gradually clear. During the daytime it will be quite sunny but significantly colder, with the zero-degree level at 2100 m. In the southern regions, nocturnal skies will be heavily overcast accompanied by a small amount of snowfall above approximately 1500 m, and during the daytime it will be partly cloudy. In the early morning the avalanche situation is quite favourable. Because the snowpack has little chance to cool during the night, the danger of wet-snow and gliding avalanches swiftly increases already during the morning. Sunday: In the northern regions, skies will be partly clear; the daytime will be rather sunny. In the southern regions skies will be overcast and a small amount of snowfall is possible above 1200 m by morning. In early morning the avalanche situation is favourable over widespread areas. During the daytime the danger of wet-snow and gliding avalanches increases somewhat in the northern and the inneralpine regions.