Of
Thursday, November 14 at 7:00 a.m. au
Friday November 22 at 9:00 a.m.
Situation
This Thursday a very deep depression named Caetano crosses France from west to east. It is associated with a significant air mass conflict between mild Atlantic air and cold air descending from Northern Europe. A remarkable snowfall for the season is taking place between Brittany and the center-east. Due to the low temperatures in these departments on orange alert, the snow sticks to the ground quite easily from the first heights. It is more difficult to maintain in urban areas. These snowfalls will often be accompanied by strong gusts and traffic conditions may be difficult, particularly on the secondary network. We expect 3 to 8 cm on average, locally 10 cm above 300 m but only 1 to 3 cm in the lowest or most urbanized areas.
At the same time, from Brittany to the south of the Loire and towards Auvergne Rhône-Alpes, stormy winds occur during the day with gusts reaching 100 to 130 km/h on the Atlantic coast, locally 150 km/h in the mountains and 90 to 110 km/h inland to the Massif Central. Corsica is still experiencing violent winds.
Observation
The episode begins. The first mixed rain and snow reached Brittany at the end of the night and are progressing towards Lower Normandy where it is already snowing this morning at 7:30 a.m. with temperatures close to 0°C, allowing this snow to hold on the ground. Be careful in the car where some collisions have already taken place. But the warm weather is growing rapidly from the west.
The wind gusts are already stormy with for example 138 km/h on the island of Ouessant as the low pressure core passes.
Evolution
SNOW ALERT
This Thursday morning
The disturbance invades the northwestern part of the country. The snow falls moderately from this early morning from the north of Brittany to the north of Pays de la Loire then strengthens over the hours, adding a few centimeters (3 to 6 cm) on the hills. The snow is more difficult to hold on the coast and in the heart of cities with 1 to 3cm. On the tip of Brittany and the south of Brittany and the Pays de la Loire, it is rain or mixed rain and snow. At the end of the morning, snow invades all of Lower Normandy and Center-Val de Loire up to the edge of Ile-de-France. The snow quickly sticks to the ground on the plateaus.
Snow is often accompanied by strong gusts of wind and makes driving conditions difficult in places exposed to the northeast wind.
Thursday afternoon
From Brittany to Pays de la Loire, the disturbance will gradually disappear. The snow zone will extend from Normandy and Centre-Val de Loire to Burgundy-Franche-Comté via Ile-de-France and the south of the Grand Est region. Snowfall is heavy from the interior of Normandy to the north of Burgundy-Franche-Comté via the south of the Paris Basin. On the plateaus from 150 m altitude, we expect 3 to 8 cm, locally 10 cm above 300 m altitude. Below 150 m altitude we expect 1 to 3 cm, locally 5-6 cm under the most intense snowfall. Traffic conditions will be difficult on untreated networks, under the heaviest snowfall and in the presence of wind.
Thursday evening
The disturbance will still concern the north-eastern and central-eastern regions, with a few centimeters on the ground expected from southern Lorraine and Alsace to Burgundy-Franche-Comté. In Auvergne-Rhône-Alpes, it will still be rain below 800 meters of altitude.
WIND ALERT
Thursday morning
The wind is blowing strongly across the entire Atlantic coast with gusts of 90 to 120 km/h, locally 130 km/h on the islands and Finistère where the gusts are more violent than initially expected: be very careful. Inland, from Brittany to Aquitaine, the wind strengthens to reach 70 to 90 km/h in gusts, locally 100 km/h on the most exposed hills.
Thursday afternoon
The wind continues to blow strong near the Atlantic with maximum gusts of 80 to 100 km/h from Brittany to Loire-Atlantique and 100 to 120 km/h, locally 130 km/h on the coasts between Vendée and Aquitaine. The wind strengthens from the southwest plains to the Massif-Central with gusts of 80 to 100 km/h and up to 120-130 km/h on the hills.
