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Avalanche bulletin through Thursday, 23 October 2014

Onset of winter in northern regions: heavy snowfall, heightened avalanche danger

Edition: 21.10., 17:00 Next update: 23.10., 18:00 Validity

Onset of winter in northern regions: heavy snowfall, heightened avalanche danger
Edition: 21.10.2014, 17:00 / Next update: 23.10.2014, 18:00
Avalanche danger
Northern flank of the Alps from the eastern Bernese Oberland to Liechtenstein, northern Upper Valais, northern Grisons, northern Tujetsch and northern Lower Engadine: storm-strength winds and heavy snowfall bringing much new fallen snow have brought the onset of winter. The avalanche danger at high altitudes is expected to increase to Level 3, "considerable". Slab avalanches can be released even by one single person. Naturally triggered avalanches can be expected. These avalanches can attain medium size in high alpine regions more than anywhere else. In addition, moist sluffs and full depth snowslides can be expected at intermediate altitudes. Mountain sports require extensive experience in the evaluation of avalanche hazards.
Northern flank of the Alps from Chablais to the western Bernese Oberland, Lower Valais, southern Upper Valais, remaining Grisons, the Ticino regions of the Main Alpine Ridge: freshly formed snowdrift accumulations can be easily triggered in some places. In high alpine regions the avalanche prone locations occur more frequently. At intermediate altitudes, moist snowslides can be expected.
Ticino south of the Main Alpine Ridge: snow lies deposited only on the highest mountains. Isolated, small-sized snowdrift accumulations need to be assessed with great care in extremely steep terrain.
Snow and weather
Snowpack
Storm-strength northwesterly winds intensely transport the fresh fallen snow. In high alpine regions, new fallen and newly drifted snows are frequently being deposited on top of an area-wide layer of old snow. Below approximately 2800 m, the ground was warm and the terrain bare of snow before the current bout of precipitation.
Weather, review to Saturday, 18.10.
From Saturday through Monday it was predominantly sunny and inordinately mild, the zero-degree level above 4000 m in some places. On Monday night above approximately 2800 m on the northern flank of the Alps, there was 20 to 30 cm of snowfall. During the day on Tuesday, it was partly sunny.
Weather, forecast through Thursday, 23.10.
Storm-velocity northwesterly to northerly winds will lodge moist arctic air masses against the Alps. On Wednesday snowfall is anticipated in all regions of the Swiss Alps except in the south, on the northern flank of the Alps the snowfall will be heavy. On Thursday, heavy snowfall is expected to persist in eastern regions. In western regions and in Ticino it will be quite sunny. The snowfall level is expected to be at 700 to 1000 m. Since the ground is still warm, full snow depths will be reached only above 1500 to 2000 m. By Thursday evening, the following overall amounts of snowfall are anticipated:
  • northern flank of the Alps from the eastern Bernese Alps to Liechtenstein, northern Upper Valais, northern Grisons and northern Lower Engadine: 60 to 80 cm; in the Glarner Alps and the Silvretta, as much as 100 cm
  • northern flank of the Alps from Chablais to the western Bernese Alps, Lower Valais, southern Upper Valais, central Grisons, remaining Engadine: 20 to 50 cm
  • remaining regions: along the Main Alpine Ridge as much as 30 cm; further to the south it is expected to remain dry
Outlook
On Friday, 24.10, and on Saturday, 25.10, it is expected to be predominantly sunny and noticeably warmer in the mountains. The avalanche danger will diminish only incrementally. Mountain sports participants can still trigger avalanches. In addition, the rising temperatures and solar radiation in the major areas of precipitation are expected to cause naturally triggered, moist snowslides to release at intermediate altitudes as well.

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