Remarkable episode of snow in the mountains since this weekend

As the depression named “Enol” passed this weekend, a polar air shift swept across France, leading to a period of showers with storms of sleet and snow. In a flow oriented towards the northwest sector, maritime polar air allowed snow to fall in abundance on our mountains from 500 to 600 m, with thicknesses of 20 to 30 cm from 1000 m depending on the massifs. In high mountains, thicknesses reach 80 cm to 1 m of fresh snow around 1800 m in the Northern Alps, and 60 to 70 cm in the Pyrenees.

Some depths of snow this Monday, December 23, 2024 © The Weather Channel

Up to 1 m of fresh snow at 1800 m altitude

It was the first real big snowfall of the season in the mountains, for the first weekend of the Christmas school holidays. This time, all our massifs are covered with a white coat with 20 to 40 cm on the Vosges and the Auvergne mountains. In a northerly wind configuration, the Southern Alps are disadvantaged and the snowfall has stopped in the Hautes-Alpes. The Pyrenees held the flow well with thicknesses reaching 70 cm around 1900 m altitude, and 50 cm at 1500 m. The whole chain benefits.

Le Grand-Bornand (1400 m) this Monday morning © Un Kette in Chamonix / Fb

The Jura mountains also benefited from significant snowfall, sometimes with 40 cm at 1200 m altitude. Generally speaking, the snow remained on the ground from 500 m altitude (sometimes with 5 to 10 cm in Franche-Comté and in the intramontane alpine valleys, such as Grésivaudan or the Annecy sector). Around 800 m altitude, we noted thicknesses of 10 to 25 cm, and sometimes even 40 to 60 cm of snow around 1000 to 1200 m, which is remarkable.

Alongside these abundant snowfalls, the wind blew like a storm (up to 135 – 140 km/h at altitude like at Bonneval or at the Col du Galibier). These storm conditions caused the formation of snowdrifts, an additional risk factor on the avalanche front. In this regard, this thick snow cover deposited on an unstabilized sub-layer is conducive to a high risk of large avalanches. This risk will slowly decrease from this Tuesday. But the greatest caution must be observed in the corridors.