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Avalanche bulletin through Saturday, 25 October 2014

Lots of snow, heightened avalanche danger regionally

Edition: 23.10., 17:00 Next update: In the event of heavy snowfall Validity

Lots of snow, heightened avalanche danger regionally
Edition: 23.10.2014, 17:00 / Next update: In the event of heavy snowfall
Avalanche danger
Urner and Glarner Alps, northern Grisons, Silvretta: The masses of new fallen and newly drifted snows can be triggered as slab avalanches by winter sports participants. These hazards prevail above the treeline on Friday, the first sunny and warm day following this round of precipitation; on Saturday, above approximately 2800 m in particular. On steep, grass-covered slopes, numerous but predominantly small-sized full depth snowslides can be expected below approximately 2800 m. In addition, moist sluffs of loosely packed snow can be expected in very steep terrain.
In the remaining regions, snowdrift accumulations are the major peril. These accumulations are to be found particularly in gullies, bowls and in high alpine regions in general; they need to be evaluated with great care. In addition, in those regions which have received greater amounts of fresh fallen snow, moist sluffs can be expected in steep terrain. Apart from the dangers of being buried in snow, the perils of being swept along should also be taken into consideration.
Snow and weather
Snowpack
In high alpine regions, new fallen and newly drifted snows were frequently deposited on top of an area-wide cover of old snow. A snowpack typical of high winter comprising several varying snow layers already prevails in those zones. Below approximately 2800 m, the ground was warm and bare of snow before precipitation set in. This favours a swift decrease in the dangers of dry avalanches; however it also favours the formation of full depth snowslides in the major areas of precipitation.
Weather, review through Wednesday, 22.10.
On Wednesday there was snowfall down to low altitudes except in the southernmost regions. In the central and eastern sectors of the northern flank of the Alps as well as in Grisons, snowfall (which was heavy in some places) persisted until Thursday midday, thereafter skies remained overcast. On Thursday in western regions and in the Valais, it was quite sunny above approximately 2200 m; in the furthermost south it was beautiful. All in all since Tuesday evening, the following amounts of snowfall have been registered:
  • eastern Urner Alps, Glarner Alps and northern Grisons: 60 to 80 cm
  • remaining northern flank of the Alps from Bernese Oberland to Liechtenstein, central Grisons, Lower Engadine: 30 to 60 cm
  • remaining regions: maximum 30 cm; in the furthermost south it was dry
Since the ground was warm before the snowfall began, the forecasted snow depths were not attained except above approximately 2000 m, even though the snowfall level was at 1000 m. Winds were blowing at strong to storm velocity from the northwest to begin with, then on Thursday from the north. In western regions, the wind slackened off on Thursday. The fresh fallen snow and, in high alpine regions, the old snow were transported intensively.
Weather, forecast through Saturday, 25.10.
On Friday it will be sunny. The wind is expected to slacken off and be blowing mostly at light velocity from the northeast. The zero-degree level will ascend to 3400 m. It will also be sunny on Saturday, before clouds move in from the northwest at midday. Winds will be light, blowing from the northwest, the zero-degree level will be at 3000 m.
Outlook
On Sunday, 26.10 and on Monday, 27.10, it will be sunny and mild in the mountains for the most part. The avalanche danger is expected to decrease, but care still needs to be given to avalanche hazards, especially in very steep terrain of high alpine regions.

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