July 29, 2021

Weather Alert: Severe thunderstorms in the southwest

Through Cyril BONNEFOY, meteorologist

Complete weather forecasts live by phone at

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From Saturday June 26 at 6:00 p.m. to Sunday June 27 at 6:00 p.m.

Situation

A new stormy degradation, potentially violent, is triggered this Saturday at the end of the afternoon in the south-west of France. This degradation is linked to the presence of a cold drop, ie a depression, located in the Bay of Biscay and which descends towards Spain. In its rotary movement, this low will bring up another storm wave this Sunday evening, potentially more extensive and more violent, which will be worth an extension to the north and to the east of this release this Sunday morning.

Observation

On this Saturday afternoon, the depression descends in the direction of the Bay of Biscay. It rains, sometimes steadily, in the north-west of France. On the other hand, thunderstorms have not yet formed in the south of our country but it is hot with values ​​varying at 2 pm between 25 and 31 ° C from Bordeaux to Nîmes.

Evolution

This Saturday at the end of the afternoon:
Thunderstorms form quickly between 7 p.m. and 8 p.m. over the central Pyrenees and the Basque Country, going up towards the Garonne, from Bordeaux to Toulouse.

This Saturday evening:
Thunderstorms rise towards Charentes, Limousin, Gers and Lot-et-Garonne. They promise to be strong in these two departments. Rainfall amounts of 30 to 50 mm can occur, with high electrical activity.

Night from Saturday to Sunday:
This stormy wave loses in intensity but goes up towards the center-west, concerning the south of the Center-Val de Loire, but in a more isolated way. These thunderstorms reached the Loire Valley progressing rapidly during the night. At the same time, heavy stormy rains affect Brittany with intensities that can reach 10 to 15 mm / h.

Sunday morning :
It is rather the lull in the southwest as thunderstorms break out from the Loire Valley to the Paris basin to Normandy.

Sunday afternoon :
It is improving in Brittany with the return of beautiful clearings but thunderstorms are still triggered from Normandy to the east of the Loire Valley, passing through the Paris basin. Other isolated thunderstorms are possible over the Massif Central. In the southwest, the sky is cloudy but the weather remains calm.

Sunday evening and following night:
A new stormy wave begins on the coast of New Aquitaine while other sometimes strong thunderstorms erupt over Auvergne. These sometimes violent storms are advancing in the direction of Limousin and Auvergne. This new, potentially more violent stormy wave will be the subject of a geographic extension to the east and north of our alert.

This stormy degradation is characterized by:
– a new risk of hailstorm to the southwest from this Saturday evening.
– from strong gusts of wind up to 80 to 100 km / h when thunderstorms pass.
– cumulative rainfall of up to 40 to 60 mm under the strongest thunderstorms.
– a new risk of mudslides and floods on saturated soils.

List of departments concerned