At the South-East, An episode of very bad weather sets in this Friday morning and especially from Friday evening to Saturday evening in the PACA region and part of the Cévennes. In a context resembling an “autumn rainy episode”, which is uncommon at this time of year, significant amounts of rain will fall in 24 hours (from 50 to 100 mm with possible local peaks of 200 mm) . At altitude, this precipitation will cause abundant snowfall above 1600 m. In the context of a holiday weekend, traffic conditions are expected to be difficult to access the resorts (30 to 50 cm of snow expected around 1800 m).
At 8 a.m. this Friday morningsome light to moderate rain is already affecting Bouches-du-Rhône and Alpes-de-Haute-Provence with intensities of 1 to 5 mm/h, but the event itself has not yet started.
A south to southeast flow rises from the Mediterranean from Friday morning to Saturday evening. In this humid and windy flow, heavy rain will fall especially from the PACA region to Drôme, to Isère and the Cévennes. At altitude, this precipitation will occur in the form of heavy snowfall from 1600 m above sea level, particularly in the southern Alps and Isère. Access to the stations may become complicated, requiring the usual precautions to be taken (special equipment). The expected accumulations are of the order of 40 to 60 cm beyond 1600 meters.
During this episode, we expect cumulative rainfall of 50 to 80 mm, with local peaks of 150 mm (occasionally 200 mm). The departments of Alpes-Maritimes and Var are the most exposed to the most abundant accumulations.
These heavy rains will at times take on a stormy character, with locally strong intensities.
Here is the chronology of this degradation in the south:
Friday morning, from 9 a.m. to noon:
The rains begin quickly in the PACA region with fairly strong easterly winds on the Côte d’Azur. The snow only falls above 1600 to 1700 m initially (Mercantour, Hautes-Alpes).
Friday afternoon (1 p.m. – 7 p.m.)
Sustained rains are widespread in the south-east, the Rhône valley and the Cévennes. The highest intensities concern the Côte d’Azur (Alpes-Maritimes). Snow becomes widespread in the southern Alps from 1600 to 1700 m altitude. The wind blows up to 80 km/h on the coast, generating strong swells (2 m).
Friday evening (7 p.m. – 12 a.m.)
Heavy rains and strong winds persist all evening and all night in PACA, the lower Rhône valley as far as the Ardèche Cévennes. In the mountains, snow falls in abundance from 1600 m, with delicate conditions on the altitude network. The south/southeast wind blows at 80 km/h with gusts close to 100 km/h on the capes of the Côte d’Azur. The sea becomes very rough with troughs of 3 m offshore.
Night from Friday to Saturday :
Weather conditions remain degraded in the south-east with heavy rain and strong winds. At the end of the night, the rains lose a little intensity.
SATURDAY : the rains will increase in intensity, becoming stormy as the cold front passes over the entire area, from 10 a.m. to 1 p.m. The east wind then blows between 80 and 100 km/h in gusts on the French Riviera. Be careful, the rain-snow limit will drop quite suddenly around 1300 to 1400 m at midday, particularly in the Southern Alps, which could complicate traffic, particularly towards winter sports resorts.