Big snowstorms and heavy precipitation on the way. This will be followed by a return to calmer sunnier weather for Christmas.
In the meantime, there is a hidden risk under the snowpack
The snowpack appears quite stable at the moment. But this may be deceptive. Several places like Val d’Isere reduced the danger rating to a rating of 2 today. However other places like Ste Foy maintained a danger rating of 3 today.
We have also picked up two danger signs today. The first is an unconfirmed report of a major avalanche released on the North Face of the Foglietta. Our early report suggests this may be bigger than the one we reported on in 2015. If we get more info we will report on it.
The second report is from snow profiles similar to, for example, one that was conducted at 2530m on the top of Solaise in Val d’Isère (and other similar altitudes in Savoie and surrounding areas). This reveals a snow depth of 175cm: Most of the snowpack is quite well bonded with different levels of hardness but the layer at the bottom, from 0 cm to 25cm above the ground, is a weak layer of facets that has little to no cohesion. These snow profiles (all generally above 2400m and on flat or North – Northeast’ish aspects) point to a low probability of an avalanche release due to the thickness of the well-bonded layers above the weak layer, but vulnerable to triggering in some places especially in areas where the top stronger layers are thinner. Releases on this weak layer next to the ground are not likely, but if it does go, it will go big (if the Foglietta report is correct, this would be such an example).
Recent history of the snowpack
Last weekend there was a big storm from the west. This scoured the west-facing slopes. See this picture of Toviere above Tignes taken on Thursday 19th December
The wind also loaded up the East facing slopes with a much thicker snow cover. See this image of the Lognon area overlooking Tignes taken at the same time. This shows how it pays to understand the historic wind direction. It will lead you to better snow. These photos are a simple reminder that after wind the better snow is on the leeward slopes. (However, it may be more dangerous, so you need to apply risk management)
The past week in the Northern French Alps has been warm and windy. Big depths of snow received last Friday and Saturday have shrunk rapidly due to the melting effects of the Foehn wind.
The wind has hardened the snow, if not scoured it off altogether in high exposed areas. Snow quality has been quite variable: On particularly warm days it’s been dense and heavy even at high altitude. At other times, in high altitude areas sheltered from the wind, it’s been nicely supporting with a lovely soft cushion on the top.
With the warm temperatures we’ve been watching our timings, and finishing our off-piste skiing early in the afternoon. The snow’s been turning to heavy slush, particularly at lower altitudes, in the afternoons. More reminiscent of April snow than December!
Poor visibility and lack of powder snow has deterred many people from going off-piste. However, whenever we’ve ventured out we’ve nearly always found conditions much better than we’d imagined, with the flat light not so bad …. with the added bonus of often having the slopes completely to ourselves!
Following the past week’s warming up and loosening of the snowpack, cooler temperatures in the next few days (at least until the beginning of next week) should firm up this looser snowpack at altitudes above 2000 m where temperatures should be hopefully be going down below freezing point.
BUT it looks as if we’re due for large amounts of snow again in much of the Northern French Alps and surrounding areas. The forecast is for very stormy weather with blizzard conditions over the weekend. With the significant precipitation which looks like continuing for several days will come a lot of natural “direct action” avalanches due to the huge quantities of snow (above 2000 m anyway).
What is the current avalanche risk in the Northern French Alps/Savoie?
At the time of writing, the avalanche risk is at a moderate 2/5 below 2200 m, and a considerable 3/5 above that altitude. However, during and after the snowstorms that are forecast, this will go up to a high 4/5 or may even become a very high 5/5. Check out definitions of what the avalanche danger ratings mean here.
The snow profile reported earlier shows why the danger rating is being kept at level 3 in some spots even though the snowpack looks stable. The avalanche on the Foglietta just confirms that.
What does this mean for off-piste skiers and snowboarders?
Looking forward, the biggest risk over the next few days will be from direct action avalanches during and just after storms. This will be the new layer of snow releasing naturally as a direct result to the loading of the new snow. If there is a weak layer on a thin snowpack (e.g. west-facing) this direct action release could go to the ground. Where the snowpack is thicker this is more likely to be the top layer of new snow.
The severity of the weather will keep most people off the mountain anyway, certainly away from the off-piste areas – unless you really know what you’re doing. The best way to stay safe from these natural avalanches is to follow the advice given by local authorities. For example, they will be closing roads and ski-runs at risk of avalanches coming down onto them.
In reality, however, more than 90% of human accidents in avalanches are due to the victims triggering the avalanche themselves. So during the time of big these big snowfalls, if you follow the safety protocols put in place by the authorities, you will be fine… at least as safe as driving on a motorway at any given time.
Where is most at risk at the moment?
Higher and colder areas under the ridges and cornices that were in the lee of recent storms (N, NW, NE, E, SE). However, the recent bulletin says the risk will evolve to all aspects. The risk below 2000m is from wet snow, the risk above 2200m is from cold dry snow releasing a slab avalanche.
What is the likely avalanche activity this week?
Direct action avalanches from new snowfall, this will be most likely on leeward slopes. The storm wind is forecast to be high to very high and from various directions: from W, NW and SW so East facing slopes will be most vulnerable. However, we suspect that the bulletin will suggest a risk on all aspects during the snowfall.
A possible impact on the weak layer revealed in the snow profile test. This would result in a very big avalanche going down to ground level
How does the forecast look for the coming week?
Unsettled over the weekend with lots of new snow. Settles down from Monday. Sunny from Tuesday and all week. So great news for the Christmas holidays.
FRIDAY 20 DECEMBER
Foehn in the morning, then a new weather system arrives bring colder weather and fresh snow.
From the Haute Maurienne, to the border peaks of the Haute Tarentaise as well as at the limit of the Hautes Alpes, the sky remains covered in cloud with light snowfall. Further west, the sky is more or less cloudy. In the afternoon, the sky gets covered everywhere giving moderate precipitation and snow from 1900m lowering towards 1500m at night (20 / 30cm towards 1800m between the evening and the following night, reaching locally 40cm at the edge of the Hautes Alpes over the 24h.).
Foehn wind blows in the morning with gusts of 50 to 80 km / h in the exposed valleys, 110 km / h in the high mountains. The wind weakens in the second half of the afternoon coming to the southwest.
Maximum temperatures: 3C to 2000m (0 near Italy), -2C to 3000m.
Isotherm 0C 2500m in the morning, down to 1600m in the afternoon.
Wind at 2000 m: S 60 km /, gusts 90/100 km / h on the ridges, weakening SWt40 km / h at the end of the afternoon.
Wind at 3000 m: S 90/120 km / h weakening SW 50 km / h at the end of the afternoon.
SATURDAY 21 DECEMBER
A short break in the weather, then unsettled.
In the morning, cloudy skies dominate, but clear spells are possible. On the other hand, in the afternoon, the sky covers up giving snow around 1700m (10 to 15 cm at night).
Maximum temperatures: 2C to 2000 m, -2C to 3000 m.
Isotherm 0 DG: 1500 m up towards 2000m
Wind at 2000m: SW 20/30 km / h.
Wind at 3000 m: W 30/50 km / h.
SUNDAY, 22 DECEMBER
Overcast with snow in from 1300 m, lowering towards 1000m (40/60 cm from 1600 m, slightly less in Haute-Maurienne). Strong wind from W then NW at altitude.
MONDAY 23 DECEMBER
Cloudy, some snow in the mountains above 1000 m
TUESDAY 24 DECEMBER:
High altitude clouds, return of clear weather
WEDNESDAY: Christmas day will be beautiful: mild, sunny and calm under high pressure.
THURSDAY 26 DECEMBER:
quite beautiful and mild, in the mountains. 0C may go to 3000m
FRIDAY, DECEMBER 27 and SATURDAY, DECEMBER 28
Maintenance of high-pressure conditions over France, with low clouds over most of France. The weather will remain sunny in the mountains and near the Mediterranean.
Tip of the week
When the avalanche risk is high, stay on and around slopes no steeper than 30°
When the avalanche danger rating is up to a 4, stay within areas where slopes are no steeper than 30°. One of the clearest signs of risk is the consequence of what would happen to you if you are taken by an avalanche, i.e. make sure there are no terrain traps around you.
Learn what a 30-degree slope angle looks like. A Slope Angel device is one of several that might help you do this by measuring it for you.
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