Off-piste snow report, N French Alps, 26th Dec 2019

What a lot of snow and wind we had.

When the weather finally cleared on Christmas day. It was glorious but frustrating for some and dangerous for others. Many were disappointed to find the snow badly wind affected and off piste conditions were difficult. Skilled people could locate the areas where powder still existed. But then they had to be aware of the dangers. As is always the case after fresh snowfall the snow was quite unstable on Wednesday. We observed a lot of recent avalanche activity especially on E or NE (leeward) facing slopes around 2500m. Recent avalanche activity is one of the top clues that things are unstable

There were reports of some avalanche accidents on 25th December. A skier was taken for a ride and injured under the Tommeuse lift in Val d’Isere (NE facing slope 2400m). Data avalanche reported an accident in the Grand Rousses where two skiers were taken for a ride at 2900m. There was a much more serious accident in Andermatt Switzerland with six skiers involved

Over the past week, plenty of natural avalanche activity was observed (or rather heard, as we couldn’t see a lot!) on slopes facing all directions. Roads were closed by local authorities due to risk of direct action avalanches coming down onto them. Areas such as Le Fornet, a couple of km east of Val d’Isere, were cut off for several days due to the risk of avalanche danger.

And a snowboarder was injured in an avalanche in St Moritz

After 4 days of wild conditions with crazy amounts of snowfall and howling winds (gusts up to 250 km/hr), things are eventually calming down. A high-pressure weather system coming in after Friday will bring much more stable, sunny weather to the Northern French Alps for the start to the New Year.

Looking forward after a little fresh snow on Friday, we expect the weather to turn more settled from the weekend into next week. Beautiful sunny weather in the mountains….

Henry describes last week’s conditions in this video of 21st December:

Off-piste skiing conditions varied greatly over the last week. By skiing in the sheltered trees during flat light days, we found fantastic knee-deep powder snow. At higher altitudes above 2000 m or so, strong winds sometimes ravaged the snow, making for very tricky off-piste skiing conditions. For example, on Christmas morning (a stunning sunny day) the snow had been wind-stiffened and densified (difficult to turn in, and easy to twist a knee). At other times it was rock hard, if not blown off the mountain altogether.

Every day’s proved different, and it’s always been worth going out. When the weather’s looked terrible from the window, the skiing’s often been fantastic, and vice versa!

Recent history of the snowpack

After all the recent snowfall, snow depths are currently very good above 1300 m or so.

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, due to large accumulations of snow and areas of dense windslab up there. With calmer weather after Friday, we expect things to continue to stabilise and for the avalanche risk to decrease.

There will be a little loosening up of the snowpack if temperatures become mild again (as seems possible next week). This could mean some more natural avalanche activity occurring, but not in the extent that it has over last week with the huge amounts of snow around.

What does this mean for off-piste skiers and snowboarders?

Read the bulletin for updates on the stabilising snowpack and any new risks that come from the fresh snow on Friday

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. Leeward slopes that got wind-loaded (E and NE) are the most risky. There is still a sign of a weakness at the base of the snowpack with faceted grains. However, this is now so deeply buried that it is unlikely to release. But if it did it would be very big.

How does the forecast look for the coming week?

FRIDAY, DECEMBER 27
Cloudy start and sunnier in the high mountains, a little colder in the afternoon.
The cloud cover gradually becomes thinner, and the clearings widen frankly in the mountains in the afternoon, above 1500-2000 m on the Prealps side, above 2500-3200 m in interior mass, remaining more shy below.
A little intense precipitation at the beginning of the morning, weakens at the end of the morning, becomes more scattered at the beginning of the afternoon, then becomes scarce.

Maximum temperatures: 6 ° C at 1000 m, 3 ° C at 2000 m, -1 ° C at 3000 m.

An increasingly starry night, except in western Savoy.
Cloud residues continue to dissipate at the start of the night, leaving the sky clearer, and the last showers disappear.
But a sea of ​​clouds persists until the end of the night over western Savoy, below 1500 then 1000 m.

Snow above 800-1000 m in the morning, or even lower under intense precipitation, rises a little in the afternoon, especially over western Savoy; above 1600 m, we expect less than 10 cm in Haute Maurienne, often 10-15 cm elsewhere, very locally 20-30 cm.

Isotherm 0 ° C rising around 1700 m during the day, 3000 m at night.
Isothermal -10 ° C: 3300 then 3200 then 4300 m during the day, 400 then 4300 m at night.

Wind at 2500 m (stronger to the West): NW to West then NNE during the day 10-80 then 10-40 km / h, NNE then NE at night 10-40 then 10-60 km / h.
Wind at 3700 m: NW then North during the day 60-80 then 40-70 km / h, North then NE at night 40-70 km / h.

SATURDAY DECEMBER 28
More or less largely sunny in the mountains, a little less cold in the afternoon. Above, a few passages of very high thin clouds, from West to East. Night more or less well starry, a little less cold. Some passages of very high thin clouds, sometimes a little dense.

Isotherm 0 ° C: 3000 m during the day, 3200 m at the end of the night.

Wind at 2500 m (stronger to the West): NE, 10-60 km / h during the day, 10-60 then 10-40 km / h at night.
Wind at 3700 m: NE during the day 50-70 then 40-60 km / h, NE to North at night 30-60 then 10-40 then 20-50 km / h.
A few gusts downwind from the high ridges.
At 1500-2000 m over the Pre-Alps, the NE wind remains moderate, sometimes quite strong until the start of the night.

SUNDAY, DECEMBER 29
Mostly sunny, a little less cold in the afternoon. Widely starry night.
The low clouds west of the Pre-Alps disappear at the start of the night.

Isotherm 0 ° C: 3100-3200 m.

Wind at 2500 m (stronger to the West): NE during the day 10-40 km / h, NE to NW at night 10-40 then 10-20 then 10-30 km / h.
Wind at 3700 m: NE during the day 20-50 km / h, NE then NNE at night 20-40 then 10-20 then 30-50 km / h.

MONDAY:
The fairly fast NE current at high altitude gradually weakens and turns to the NW Probable morning greyness at lower altitudes over western Savoy, rather sunny above.
Isothermal 0 ° C around 3300-3500 m.
TUESDAY:
WNW’s weak current turns north and weakens further.
Probable morning greyness over western Savoy, sunny above with some cloudy periods.
Isotherm 0 ° C down from 3300 m to 2900 m.

WEDNESDAY:
The wind from North to NE becomes very weak and can take a WSW trend. Probable morning greyness over western Savoy, rather sunny above.
Isothermal 0 ° C slightly increasing, around 3100 m.

THURSDAY:
The very weak wind takes a western trend and accelerates a little.
Probable morning greyness over western Savoy, sunny above, and some cloudy periods, especially at night.
Isotherm 0 ° C down to 2700 m.

FRIDAY 3 and SATURDAY JANUARY 4
The moderate west wind weakens and turns to WNW. Cloudy periods
Isotherm 0 ° C around 2400-2700 m.

Tip of the week

Learn the definitions of the avalanche danger ratings here.

When it’s at a 2 or 3 you still need to apply the decision and risk reduction points in our framework/checklist if you want to keep things acceptably safe. Here’s a link to a PDF version to the framework: henrysavalanchetalk.com/wp-content/uploads/2018/11/2018-HAT-Framework-A5.pdf

The post Off-piste snow report, N French Alps, 26th Dec 2019 appeared first on HAT.