Snowfall, relatively rare for the season, is expected on an axis going from Brittany to Franche-Comté. Météo-France also warns of violent winds further south.
This is the first major episode of the season. A significant wave of ice and snowfall is expected on Thursday, November 21, accompanied by a drop in temperatures. The Caetano depression, at the origin of this cooling, will “temperatures drop to mid-winter levels (…) comparable to January averages”according to Météo-France. The institute has placed on orange alert for Thursday an axis going from Côtes-d'Armor and La Manche to Haut-Rhin and Doubs, passing through Ile-de-France, as well as two Alpine departments. These snowfalls are “early” more “do not present any exceptional character”nuance Météo-France with France Télévisions. In addition, 17 other departments are placed on orange alert for violent winds, on an axis going from the Atlantic side to Savoie. Franceinfo takes stock of the expected disruptions.
“Snow and ice” vigilance in 32 departments
The first snowflakes should fall on Normandy and Brittany, before the phenomenon moves eastwards during the day on Thursday, affecting Ile-de-France, the Centre-East, then Franche-Comté and the south of Alsace. In anticipation, Météo-France announced on Wednesday the placement on orange “snow-ice” vigilance of 32 departments for Thursday.
The alert will come into effect between 6 a.m. and 11 a.m. depending on the department, and will last at least until midnight in most of them, according to the institute's interactive map. However, snowfall could begin during the night from Wednesday to Thursday, explains the Météo-France bulletin. “An extension of this vigilance to some neighboring departments nevertheless remains possible in future updates”emphasized the forecasting body Wednesday at midday(New window), ,.
It is still difficult to determine with certainty the snow depths and their hold on the ground. We expect 2 to 5 cm in the plains, locally up to 10 cm above 200 to 300 meters above sea level, and up to 15 to 20 cm in the east of Franche-Comté, Météo-France details on Wednesday .
Vigilance for violent winds in 17 departments
On Wednesday afternoon, Météo-France also decided to place 17 departments on “wind” vigilance. The phenomenon will begin along the coast between Loire-Atlantique and Gironde, from 8 a.m., then move eastwards throughout the day, on an axis crossing France to Savoie and Haute -Savoy. The phenomenon is described as a “winter storm” of an observed intensity “several times a year”.
On the coast, the forecaster mentions gusts between 100 and 120 km/h, and which could reach up to 130 km/h. “on exposed islands and capes”. Inland, they will be around or above 100 km/h, with peaks around 110 km/h. At altitude, Météo-France estimates that winds could reach 110 to 130 km/h on the Massif Central and more than 150 km/h on the highest points of the Alps.
Disturbances linked to Caetano depression
The snowfall and the risk of icy conditions that accompany it are linked to the passage of the Caetano depression, with the arrival from Wednesday of a “polar air mass” causing temperatures to drop. These latter “should peak between 5 and 10°C at the best of the day, i.e. values comparable to the January averages”warned Météo-France on Tuesday.
This depression will cause a “air mass conflict” which also explains the violent westerly winds expected south of the affected area. This will result in temperatures “particularly contrasting” between the northern half of France and the rest of the territory, where Météo-France sometimes expects more than 15°C around the Pyrenees and the Mediterranean.
Consequences in transport
If the snow cover in the plains, and particularly in the city, will not be as spectacular as in the mountains, Météo-France is still warning of the consequences of snowflakes and ice on transport. “A sticky snow depth of just a few centimeters can seriously disrupt or even block road, air and rail traffic.“, reminds the meteorological service. In Paris, it could fall 1 to 3 cm of snow, but its Staying on the ground will depend on the extent of the falls during the night from Wednesday to Thursday. In addition to delays linked to weather conditions in the capital, there will perhaps be disruptions on several RER lines and suburban trains on Thursday, due to a call for a strike at the SNCF.
The Normandy region announced “suspend school and commercial transport lines” all day Thursday, in Orne, Manche, Calvados and Eure. In Eure-et-Loir, school transport will also be at a standstill, according to the prefecture.
Snow also expected in the mountains, and a risk which could continue on Friday
Although the plains are affected by snowfall, it will be more abundant on the summits, including in departments which have not been placed on orange alert, notably in the Southern Alps. “Snow could fall as a result and we risk finding between 30 and 50 cm of snow from 2,000 m”specifies Vincent Latu, forecaster at the Northern Alps center of Météo-France, with France 3. The institute predicts snowflakes in municipalities located at an altitude of 500 m or more, notably in Gap (Hautes-Alpes).
According to Météo-France, the risk linked to ice could continue on Friday in part of France. “In a context of possibly still snowy ground associated with cool temperatures, the risk of refreezing in the northeast half is quite significant”explains the meteorological service. “A few snow showers” could also occur in areas already affected the day before. A “powerful redoux” is expected during the day on Saturday, but the cold could persist longer in the north-east of France.
