Off-Piste Snow and Weather Report 21st Dec 2018

For Savoie and the Northern French Alps

Milder days ahead, sun snow and rain

What a great and varied off-piste week we’ve had! Conditions have sometimes been excellent with cold dry light powder skiing in good visibility (often bright sunshine). At other times it’s been much trickier skiing in heavy and humidified snow. We’ve also had some days of flat light and tricky route-finding. We even had to get the compass out once in an area we’ve skied hundreds of times!

A snowy, sunny, (rainy?) milder Christmas

It looks as if the weather’s going to become quite varied after Friday, with temperatures due to rise. We’re due for quite a bit of fresh snow/rain, along with strong West to Northwest winds, particularly at high altitude.  Some days will feel quite nice, some not so. All this will affect the quality and stability of the snow. The weather forecast we make here is pretty unreliable this week. I expect it will change every day.

At HAT we emphasize that the vast majority of avalanche accidents involve cold, dry snow slab avalanches triggered by the victim on North’ish facing slopes in December, January and February. We emphasize this to counter the widespread misunderstanding that avalanche danger is mainly related to rising temperatures. This is simply not true.

So over the last two weeks, we’ve been talking about issues with an unstable snowpack due to cold weather and a weak layer. There have been some very close calls by off-piste skiers, who have triggered avalanches especially on ‘bluebird days’ after fresh snowfall. Thankfully, as far as we know, there have been no fatalities, but there very well could have been. Most of the time, nothing happens. However, just because nothing happens to the vast majority of people, that doesn’t mean there’s not a danger. See Henry’s previous blog on this subject.

Risk of natural wet snow avalanches

This weekend, freezing levels are forecast to rise above 2500 m at times in most of the N French Alps. We will see a rapid rise in temperature, along with rain, snow, sun etc., this will create a risk of spontaneous, natural avalanches – especially just after a snowstorm. These will not be triggered by skiers but happen spontaneously, especially below 2300m.

Natural wet snow avalanches, that release on steep slopes due to rain and a big increase in temperatures, during and just after snowstorms, can and do cause tragic accidents. We need to keep an eye on this over the weekend and into next week (as well as the other issues of long term instability caused by cold temperatures that we’ve mentioned in our last two off-piste snow reports!)

With all the new precipitation, this kind of instability is going to be a real concern for off-piste skiers and snowboarders who are out in avalanche terrain this coming week. 

Remember to check the avalanche bulletin before you go off-piste. See our descriptions of what all the avalanche danger ratings mean.

Detailed off-piste weather forecast for 21 – 29 Dec

THURSDAY 20 DECEMBER
Clouds are replaced by few clearings around 10-11h. Clouds return with some snowfall in the afternoon and evening until around 21h / 22h. 1 to 5cm to 1500 meters. Some gusts of SW at 40-50 km / h on the summits. Maximum temperatures +4 to 1000 meters, -3 to 2000 meters and -9 to 3000 meters. Strong frosts are present at altitude (slippery roads). Minimum temperatures -2 to 1000 meters, -5 to 2000 meters and -10 to 3000 meters.

FRIDAY 21 DECEMBER
Clear until 1100 then Clouds bring steady and moderate precipitation throughout the afternoon and the following night. Initially, snow/rain line is 800-1000 meters then 2000m meters then lifts 2300 m in the night. 10 to 25cm snow around 2500 meters (5 to 15cm lower). The wind rises during the day, the gusts being close to 50/80 km / h after 10-11h approximately.

0 ° C: 1500 then rising to 2400 meters.
Wind at 2500 m: West at South-West 20 to 50 km / h.

SATURDAY 22
Milder day, some cloud some sun. The many clouds in the early morning becoming thinner with some clearings At the beginning of the night, the skies clear. Maybe a few snowflakes
The wind from West to NW remains strong in very high mountain, and lower on the SE of Savoie, At 2000 m in the Prealps, the westerly wind is still moderate in the morning, then weakening.
0 ° C: 2300 then 2100 m during the day, 2500 m at the end of the night.

SUNDAY 23 and MONDAY 24
Winds WNW then WSW then NW at altitude, cooler on Monday.
Sunday, large clear spells,
Monday, partly sunny; cloud moving in later, expect precipitation in the night
0 ° C reaches 3000 m Sunday evening, then lowers Monday, and the snowflakes reach 1500 m Tuesday in the early morning.

TUESDAY 25 and WEDNESDAY 26
Wind from NW turns to the north, weakening little by little and softening.
Tuesday, a little sun; snow diminishes in the afternoon;
Wednesday, sunnier at least in the mountains, possible
The 0 ° C isotherm approaches 1500 m Tuesday, then goes back to 2700 m Wednesday at night.

THURSDAY 27 and FRIDAY 28
The wind from North to NW at altitude, a bit cooler. Days largely sunny in the mountains; Isotherm 0 ° C in slight decline, around 2300 m.

Tip of the week

See our HAT Risk Reduction Framework / Checklist and check out our on-line talk which explains it all.

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