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Avalanche danger forecast for
Monday 12/18/2017


AVALANCHE DANGER   new snow on the borders: hidden windslabs, be careful!
Monday 12/18/2017
The avalanche danger is 3-considerable on most of the regional territory, 2-moderate from the Cogne Valley to the medium valleys of Lys and Ayas.
Typical avalanche problem: wind-drifted snow.
For the morning of Monday, expected light snowfall with strong wind from NW (then from the afternoon from NE in decline), slightly more intense along the border reliefs with France and Switzerland. The new snow makes it difficult to identify pre-existing slabs and to form new ones, especially beyond the edge of the forest on the eastern and southern aspects.
In areas with danger level it is 3-considerable, above 2200 m, it is likely to cause the triggering of soft and hard slabs of considerable width and thickness already at the passage of a single skier, both on steep open slopes and inside the forest clearings, in particular at the eastern aspects,at the eastern and southern expositions (locally also the west) which are more heavily overloaded by the wind. On very steep/extreme slopes, in the gullies, and in slope changes, it is possible to release slabs, even at a distance with high overload, involving all the snowpack below down to the weak basal layer. The hard slabs are often well visible, spread over 2400-2600 m, where the snow distribution is even more irregular, while the soft ones are in an intermediate band between 2100 and 2600 m. These latter are difficult to detect and therefore can be very insidious.
In the outdoor activities a good local evaluation of the avalanche danger is required and an accurate choice of the itinerary.
In areas with the danger level is 2-moderate the slabs are much less widespread and less thick and the triggering can occur with high overload, from very steep slopes above the tree line.
It 'expected a limited avalanche activity, especially along the border ridge with France and Switzerland, still windslabs and loose snow avalanches mainly of small size, in single cases also of large size with an important aerosol.

Avalanche danger trend: light decrease, Tuesday sunny with moderate / strong winds from NE, slabs in hardening.
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

GENERAL CONDITION
updated to 12/15/2017
  strong wind at high altitude - new windslabs - several whooms surveyed
Snowcover and weather
Since thursday evening new precipitations throughout the region, temperatures have increased (close to 0C at 1500-1700 m), the rain/snow limit rose at 1000-1100 m. The snowfall was accompanied by very strong western winds that are still present, even if slowing down, so it is difficult to understand the exact extent of the snowfall. It has been more intense in the NW areas of the region, in Valgrisenche and in the top of Valtournenche where, at 2000 m, 25-35 cm of fresh snow have been measured, 20-25 cm in Val d'Ayas and Valle del Lys, 10-15 cm in the central valley and in the Gran Paradiso valleys, 5-10 cm in the Champorcher and Champdepraz valleys.
Current amounts of snow on the ground at about 2500 m:
- 100-160 cm in D sector bordering with France and Switzerland (from Valgrisenche to the high Valtournenche);
- 70-90 cm in C sector (Gran Paradiso valleys);
- 60-90 cm in A sector (central valley of Valle d'Aosta);
- 40-80 cm in B sector (Champorcher, Gressoney and Ayas).

Snowpack
The recent snow rests on loose snow not yet settled and well bonded. It is light and dry above 1600-1800 m, while it is humidified at lower altitudes. The strong western winds, still present, are eroding a lot of new/recent snow (also 50-60 cm eroded) and building up widespread windloads mainly on astern aspects above 2100-2400 m.

Avalanches observed
Between Thursday and Friday small to medium sized avalanches of loose snow and surface slabs have been reported. A powder avalanche that reached the valley floor has been surveyed in Val di Rhmes.

Skiing conditions
In the west of the region a lot of powder, light and dry, beautiful to ski especially below the limit of the forest where the wind was less intense; more in altitude it is inhomogeneous: potentially unstable wind accumulations alternate with bumps, ridges and open slopes strongly eroded (especially those exposed to the west). Less snow moving eastward; in the south-eastern sector a basal snowpack layer is often practically absent, it does not guarantee not to touch stones with skis.
It is however important to move with caution in the choice of routes and in exploring the slopes and this also applies to those who go with snowshoes.
Weather forecast
Snow and avalanche bulletin n 18 issued on 12/17/2017 at 00:00 p.m.
Snow and avalanche Bulletin: +39 0165 776300
Weather Bulletin: +39 0165 272333
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