Weather Alert: Bad weather in the south: heavy rain, strong wind and snow in the mountains

From Monday March 25 at 12:00 to Tuesday March 26 at 6:00 p.m.

Situation

A vast low pressure system is setting up over the Atlantic and spilling over into western Europe. It generates a strong southerly current disturbed in the south-eastern quarter of France from this Monday evening to Wednesday morning. Heavy rains are blocking the Cévennes massif, generating very significant accumulations, up to 150 mm. This is the 5th Cevennes episode since the beginning of February.

The autan and the southerly wind set up from Midi-Pyrénées to the south of the Massif Central in Provence with gusts of up to 100 km/h between Monday evening and Tuesday afternoon. At the seaside, these turbulent winds risk causing submersion phenomena.

More rain will return to the PACA region and to a lesser extent to Corsica, with heavy accumulations also expected during the night from Monday to Tuesday until Wednesday morning. We expect up to 50 to 80 mm in the Maritime Alps. Snow will fall in abundance above 1300 m in the south of the Alps. Due to this bad weather, our alert is extended to the Côte d’Azur and the south of the Alps this Monday at 9 a.m.

Observation

This Monday morning at 8 a.m., the depression responsible for the bad weather to come is deepening rapidly, plunging south of Ireland. It’s raining on the Breton tip.
The episode of bad weather in the south has not yet started. The Autan wind rises in Occitanie on the reliefs of the Tarn with 72 km/h measured in gusts in Sorèze at 8 a.m.

Evolution

This Monday afternoon, the south wind and the autan suddenly strengthen in Midi-Toulouse. At the same time, the rains set in between the Pyrenees, Languedoc-Roussillon and Provence.

This Monday evening, the wind begins to weaken between Midi-Toulouse and the south of the Massif Central, but strengthens in Provence. The rains are increasing in Languedoc and the Cévennes.

During the night from Monday to Tuesday, the wind reaches its peak of intensity between the Var coast and the Hérault coast with gusts reaching 100 km/h. Waves of 3 to 5 m rise at sea and cause risks of submersion. The rains are getting stronger in the Cévennes. In the Alpes-Maritimes, the rains take on a marked stormy character.

It is Tuesday that the situation is the most degraded with violent winds in Provence, at nearly 100 km/h in the morning and large breaking waves along the seaside. The rains are intense in the Cévennes, accentuating the risks of hydrological reactions. This heavy precipitation continues until Wednesday morning east of the Rhône, between the Var, the Alpes-Maritimes and the south of the Alps. Snow falls heavily above 1200 to 1500 meters.

In the night of Tuesday to Wednesday, sustained and occasionally stormy rains continue in the southeast. With the cooling of the air mass, the snow descends to increasingly lower altitudes in the Cévennes and the south of the Alps, from 800 to 1000 meters.

Wednesday morning, the disturbance quickly evacuates towards Italy and Switzerland early in the morning. Snow falls from 600 meters above Grenoble, Chambéry and Albertville.

Over the entire episode, we expect:

– cumulative rainfall of 100 to 150 mm on the Cévennes peaks, which is equivalent to 1 month of precipitation
– snow depths of 40 to 60 cm in the southern Alps, with a high risk of avalanche
– maximum gusts of 90-100 km/h from Midi-Toulouse to the south of the Massif Central in Provence
– a strong swell of 3 to 4 m around the Gulf of Lion to the Provencal coast

List of departments concerned