A mainly dry week for the first week of 2020, with sunshine and cloud
Over the last few days we’ve been basking in wall-to-wall sunshine and mild temperatures for the time of year. Most of the off-piste snow within easy lift access has been completely tracked out, so we’ve taken to ski touring to find the best snow. With a very little fresh snow forecast next week, it looks as if we’ll be getting very fit and doing loads more walking with the use of touring skis and skins.
Ominous-looking glide cracks (frown-shaped brown cracks in the snowpack that go right down to ground level) have been appearing all over the place. Certain slopes seem more prone to these, like steep slopes between 2000 to 2700 m altitude, especially those which are grass-covered in the summer. (Bent over grass provides a smooth surface that snow can slide over easily).
Sometimes these glide cracks just appear and do nothing, but quite a few of them have been releasing, particularly in the warm afternoons. They can be quite large in size. They’re not so much a danger to off-piste skiers for reasons mentioned below, but they present a real nightmare for ski resort authorities and for avalanche forecasters in that:
- It is impossible to predict when, or even if, they will release
- They are extremely difficult to control by artificial triggering (i.e. by avalanche blasting), so if they appear above a ski piste the piste patrol service will often close the piste, especially later in the day as temperatures rise
- If they do release, they can potentially do a lot of damage
We feel that there’s almost been an over-emphasis by avalanche forecasters on how much danger glide cracks actually pose to us, as off-piste skiers and snowboarders. As we say all the time, 90 percent of avalanche accidents (i.e. avalanches where skiers are taken) are triggered by the victim/s themselves. But glide crack avalanches release spontaneously by themselves. Even preventative avalanche blasting can’t move them, and they are not triggered by skiers passing by.
Of course, we’re not saying not to watch out for them. As off-piste skiers, we certainly need to treat glide cracks with respect. We certainly shouldn’t be picnicking under them, and especially not walking up beneath them.
Notice we say these are not so threatening to off piste skiers. But are a concern for the piste patrol. So keep off closed runs, ski past them quickly if off piste, do not hang around underneath them. Be worried when there is warming and direct sunshine.
Occasionally there is human involvement when glide cracks release, as happened on 31st December in the Aravis mountains near Megève. The skiers did not trigger this avalanche – it happened spontaneously – but they were on the slope below it. Report in French on the Data Avalanche website.
Glide crack avalanche in the Aravis (Haute Savoie). Photo by Sébastien Carle. Glide crack avalanche in the Aravis (Haute Savoie). Photo by Sébastien Carle.
In our previous blog we discuss a snowpack test done by Avalanche Expert, Alain Duclos. According to recent research the fact that the weakest point in the current snowpack is at the interface with the ground suggests that we will continue too see significant ‘glide crack’ activity over the next few days and into next week.
Recent history of the snowpack
We haven’t had any fresh snow for a week, and temperatures have been quite mild for the time of season. Off-piste snow depths in the Northern French Alps are still good above 1500 m. Overall the snowpack has stabilised, as Alain Duclos’s snowpack test shows.
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. It will probably continue at this level over the next week, or could even go down to a 1/5.
What does this mean for off-piste skiers and snowboarders?
With little or no fresh snowfall expected, and a stabilised snowpack, now is a good time to do some off-piste touring to find the best untracked snow.
Where is most at risk at the moment?
The highest risk to skiers and snowboarders will, as always, be on steep slopes exposed to terrain traps.
Watch out for the glide cracks. While these are not a sign of snowpack instability (despite their ominous appearance), you certainly wouldn’t want to hang around under them for long, or tour up underneath them.
How does the forecast look for the coming week?
This forecast from Meteo France does mention some snowfall, but do not get too excited about this. It will amount to very little. More likely to deliver a few annoying clouds than any material snow.
FRIDAY 3 JANUARY
Less sunny, a little less cold in the afternoon. High and slightly thick cloudy periods in the mountains, and decrease slightly in the morning.
Before nightfall, a cloud cover below 3600 m, begins to overflow from Bugey, it gradually extends to the massifs and interior valleys, giving very weak showers especially over the West and North of Savoy, then dissipates little by little from the middle of the night. At the end of the night, a few cloudy banks remain, especially over western Savoy below 1000-1500 m.
It snows above 1500 then 1100 m (less than 5 cm).
Maximum temperatures (on southern slopes): 8 ° C at 1000 m, 6 ° C at 2000 m, 0 ° C at 3000 m.
Isotherm 0 ° C: 2800 then 2300 m during the day, 1800 then 2000 m at night.
Isothermal -10 ° C: 4400 then 4000 then 4300 m.
Wind at 2600 m (stronger to the West): SW then West during the day 10-40 then 10-20 km / h, West then NW then NE at night 10-20 then 10-40 km / h.
Wind at 3700 m: West to WSW during the day 30-40 then 40-60 km / h, WNW then North at night 40-70 then 60-80 then 50-60 km / h.
SATURDAY JANUARY 4
Mostly sunny in the mountains, even in the interior valleys, a little colder in the afternoon. A few residual cloud patches in the early morning, especially over western Savoy below 1000-1500 m.
Then other more numerous clouds spread over the Avant-Pays at the end of the morning then to the Pre-Alps or even the Combe de Savoie in the afternoon and at the end of the day, below 1000-1300 m; they persist at night, lowering a little. Above, a few passages of very high thin clouds, until the start of the night.
Isotherm 0 ° C rising around 2500 m during the day, 3400 m at night.
Wind at 2600 m (stronger to the West): NE then North during the day 10-40 km / h, North then NE at night 10-40 then 10-60 km / h.
Wind at 3700 m: North then NNW during the day 50-70 then 30-50 then 50-60 km / h, NNW then NNE at night 60-80 then 40-60 km / h.
Some gusts sometimes strong downwind of the high ridges.
SUNDAY JANUARY 5
Most sunny in the mountains, even in the interior valleys, less cold in the afternoon. The numerous cloudy residues in the morning over western Savoie, below 800-1000 m, partially dissipate during the day, and may even rise a little at the end of the afternoon, then dissipate more clearly in the night. Above, the sky remains clear, until the night.
Isotherm 0 ° C around 3400 m.
Wind at 2600 m (stronger to the West): NE during the day 10-50 then 10-30 km / h, becoming very weak at night and turning to the South.
Wind at 3700 m: NE to North, 40-60 then 20-30 km / h during the day, 10-20 km / h at night.
At 1500-2000 m on the Pre-Alps, the moderate NE wind during the day, weakens at night and turns to the South.
MONDAY 6th Jan
The weak wind of NNW in altitude turns gradually to the West and becomes fast. Very sunny day, little morning greyness; the sky is covered in the night, giving the some showers at the end of the night.
The 0 ° C isotherm lowers around 1900 m (at least) and the snow lower.
TUESDAY 7th Jan:
The fast west wind turns to the NW and barely slows down. Not much sun; the numerous clouds give light precipitation, even at night. The 0 ° C isotherm lowers a little further, then rises at night around 2700 m (at least).
The snow follows more or less easily.
WEDNESDAY 8th Jan:
The NW wind remains fast. Little sun, and light precipitation.
The 0 ° C isotherm goes down to 2300 m (at least).
THURSDAY 9th Jan :The fast wind turns to the WNW.
The 0 ° C isotherm approaches 3000 m then descends.
FRIDAY 10 and SATURDAY 11 JANUARY
The fast wind of WNW turns NW and becomes weak. Showers (especially Friday), and sunny spells (perhaps more beautiful on Saturday).
Isotherm 0 ° C down around 1800 m (at least) then up around 2400 m.
Tip of the week
Don’t spend time hanging around below glide cracks. Don’t picnic under them, and don’t walk up underneath them.