Snow and avalanche bulletin n° 29
issued on 1/30/2015 at 00:00 p.m.
 

valid 72 hours out of controlled and open ski runs
Next update on 02/02/2015

GENERAL CONDITION   Snowpack very complex and fragile + new snow + strong wind from NW =
danger level 4-strong in the NW area !
  Snow height [ cm ] Ta
[°C]
Last
snowdrift event
Last snowfall Continuous snowcover above
[m a.s.l.]
Ground level New
h 07:00 h 07:00 h 24 h 07:00
2000 m 2500 m 2000 m 2000 m Shady Sunny
A - Central Valle d’Aosta 40-110 90-120 10-20 -8 1/30/2015
moderate/strong from NW
1/30/2015
valley floor valley floor
B - Gressoney, Ayas, Champorcher Valleys 40-120 120-190 5-15 -9 1/30/2015
moderate/strong from NW
1/30/2015
valley floor valley floor
C - Rhêmes, Valsavarenche, Cogne Valleys 60-90 70-120 15-35 -9 1/30/2015
moderate/strong from NW
1/30/2015
valley floor valley floor
D - Alpine ridge 50-120 60-210 30-60 -10 1/30/2015
moderate/strong from NW
1/30/2015
valley floor valley floor
The larger amounts of fresh snow last night were recorded in areas of Mont Blanc, Gran San Bernardo, La Thuile, Valgrisenche and Rhêmes Valley, with 40-60 cm between 1500 and 2500 m, then the amounts gradually decrease moving toward the eastern Aosta Valley area. The new snow goes to lean on recent snow of the previous days: the result is that in the western sector, above 2300 m, especially in Courmayeur, La Thuile and Valgrisenche areas, the amounts of loose snow reach and exceed one meter. Also today still light snowfall at the border ridges and moderate/strong winds from NW, which are winddrifting the snowpack, mainly with soft accumulations at SE exposures above 2300 m: in these locations artificial releases are reported, even at the passage of a single skier, affecting the layer of recent loose snow. Also natural release of loose snow, medium sized, above 2300 m at all aspects are reported. The avalanche danger level is equal to 4-strong in the areas of Mont Blanc, Gran San Bernardo, La Thuile, Valgrisenche and Rhêmes Valley, especially with regard to the artificial but also for the natural release.
Structure and snowpack stability: at all aspects above 2300 m, in correspondence of slope changes anunder the ridges, new accumulations generally soft are present and growing and rest on recent loose snow, and thus, with poor resistance. Especially in the less snowy areas, above 2200-2400 m, there are always old persistent hard slabs, even large sized, covered and overloaded by the new snow and associated with a inner snowpack structure very complex and fragile, consisting in alternating crusts (wind and melt/freeze) and weak layers (faceted crystals and depth hoar) with very low resistance.
Weather forecast Show map
FORECAST   Still strong wind from NW + new/old slabs alternated with weak layers =
4-strong for artificial release !
Saturday 1/31/2015
Natural avalanche release activity: is forecast mainly associated to the sunshine, with many small and medium-sized avalanches of recent loose snow at all aspects above 2300 m, although it may also occur that, from higher altitudes at E and S aspects, spontaneous release slab avalanches, medium and occasionally large, can reach the valley floor, where the topography is favorable and especially in the Mont Blanc area, but the impact of these events is mitigated by the absence of snow at the lower altitudes.
The artificial triggering of new slabs is probable at the single skier/hiker passage, while the old ones can mostly be released by high overload: the release probability increases significantly at E and S aspects and rising in altitude.
It is possible to trigger slab avalanches, both soft and hard, even large sized, able to simultaneously affect different levels in the snowpack, on the basis of the overlapping new and old slabs alternated with weak layers. For Saturday and Sunday the degree of danger is forecast at 4-strong for the artificial release in the areas of Mont Blanc, Gran San Bernardo, La Thuile, Valgrisenche and Val di Rhêmes; 3-considerable elsewhere (don't underestimate it !): it is therefore recommended extreme caution in the backcountry/skitouring activities on the whole Region: for correct choices it is required a very good local knowledge of the mountain areas, of the ski-tours and tracks and of the history of the snowpack life until today.
Sunday 2/1/2015
Monday 2/2/2015
KEY Critical slopes altitude and aspects Rising avalanche danger during the day
Hazard scale
5
VERY HIGH
4
HIGH
3
CONSIDERABLE
2
MODERATE
1
LOW
Answering service: snow and avalanche Bulletin +39 0165 776300 - Weather Bulletin +39 0165 272333
For an accurate interpretation of the Bulletin, a specific guide is available at www.aineva.it/guida.html