STORM MONITORING: a line of heavy storms is sweeping across Burgundy, a return to calm elsewhere

Par Pascal SCAVINER, meteorologist
Posted 6/22/22, updated 6/22/22 10:40 PM

Since this weekend, a large part of France has fallen into a lasting stormy period with bad weather linked to violent hailstorms, intense rains and stormy gusts of wind. To help you in your decisions, we are doing a new follow-up on the stormy evolution of this Wednesday evening.

At 10:40 p.m., the storms have almost all disappeared, except between the north of Aude going up towards Lozère and Isère. These storms are weak and scattered, giving good rains without any aggravating character now. On the other hand, Burgundy and Morvan suffered the passage of a very active line of storms. The regions of Digoin, Montceau-les-Mines, Geugnon, Le Creusot, Autun, Paray-le-Monial should expect to experience a new episode of hail between 11 p.m. and Thursday 1 a.m.

9:30 p.m., the situation is beginning to improve. This is the case in the northwest, between the south of Brittany, the south of Normandy and the north of the Pays de la Loire, where the rains lose their stormy character. Nevertheless, these continuous rains are still of moderate intensity (2 to 5 mm / h) and can generate significant runoff, even local flooding.

On the Loiret, a few storms are trying to develop, but they remain very localized. Same situation in Hauts-de-France, where showers are developing, but should quickly disappear.

From Burgundy to Auvergne-Rhône-Alpes, stormy activity is losing intensity. Most of the bad weather is therefore passing. But be careful, because from Aveyron and Haute-Loire to Isère and Savoie, there remains strong instability which continues until at least 11 p.m.

The situation is more delicate between the Nièvre and the Allier, swept away by a strong line of storms. These storms last a short time (30 minutes) but they are likely to cause hailstorms. This line of thunderstorms will cross the entire Saône-et-Loire by 11 p.m. This department, already hit by repeated hailstorms since Monday, is therefore likely to suffer bad weather in the next few minutes.

At 8:30 p.m., the situation remains just as unstable in the east and south of France, with heavy storms. Strong thunderstorms also affect Brittany and part of the Pays de la Loire and southern Normandy. This situation is still linked to a low pressure system in the Bay of Biscay.

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As a result, rainfall intensities are exceptional under these storms.

Obviously, such quantities of water falling in such a short time cause flooding, this is currently the case in Lyon.

In Roanne, the situation turned into an apocalypse with huge hailstones in the area. Many vineyards are again devastated, like yesterday in the Loire department.

The conditions remain very unstable for the next few hours over all regions extending from the northwest to the southeast via Burgundy, that is to say all along the stormy front.

To 19h, in Mayenne (53) nearly 76 mm of rain fell between 10 a.m. and 7 p.m. It’s 2 times more than a month of precipitation in June and surely a record in 24 hours.

At 6:30 p.m., the strong thunderstorms affecting the northeast and particularly the departments between the Swiss border (see example above of a violent thunderstorm threatening Neuchâtel in Switzerland) and the Vosges, are slowly moving away towards Germany. In particular, they gave, in less than 1 hour, 36 mm of rain on Maîche (25). They caused flooding locally in Côte d’Or.

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On the other hand, the electrical activity is just as important between Morbihan and Beauce (south-east of Île-de-France) with locally some flooding in Mayenne with there also 30 mm in less than 1 hour. Part of Eure-et-Loir and Morbihan are also heavily affected.

On the south, a stormy axis is organized between Lozère and Saône-et-Loire with locally heavy rains and moderate hailstorms.

Overall, hailstorms should generate less hailstones than the past two days. If the electrical activity will remain important this evening, it is more intense rains that must be feared locally in less than 1 hour,

A 17h20, activity is still strong in Franche-Comté with heavy rains. We note 32 mm in 36 minutes on Vesoul, the equivalent of 32 liters per square meter. This corresponds to a third of the rains for a month of June.

A 16h20, two opposite areas are affected by violent thunderstorms. On the one hand to the northwest, in a triangle between Le Mans/Rennes/Nantes, and on the opposite between Macon/Langres/Belfort. On the rain side, 30 to 35 minutes were recorded in several places in the Sarthe, and this, in less than 1 hour, such as in Thorée-les-Pins and Sablé-sur-Sarthe. The wind sometimes blew in very strong gusts in the Jura, as in Tavaux and Lons-le-Saunier, between 70 and 80 km / h

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A 15h30, violent storms over Dijon which quickly move towards a Haute-Marne/Jura axis

A 15h, the Saône-et-Loire was once again heavily affected with strong hail activity and strong winds, but also with very heavy rain and thunderstorms. He fell in particular 30 mm in 18 minutes on Villefranche-sur-Saône. Heavy rains are observed in the Rhône, in St-Didier-sur-Beaujeu and Onlay in the Nièvre. The strongly stormy axis extends from Lyon to Langres in Haute-Marne, and shifts to the northeast.

Between 2 p.m. and 3 p.m., winds of up to 101 km/h were measured in the Allier.

A 14h15, the moderate thunderstorms extended from the middle Rhône valley to the central Alps going up towards Dijon then towards Le Mans. Other isolated cells are observed between Reims and Nancy.

In the next hour, the most active cells will develop between Dijon and Lyon with a risk of heavy hail between the east of Ain and the south-east of Saône-et-Loire

A 11h 45, organized cells are observed between Montluçon, strongly affected yesterday, and the region of Châteauroux. The electrical activity is quite significant and the rains sometimes heavy in less than 1 hour.

These stormy rains should rise slowly towards the north over the next two hours, partially decreasing in intensity, while others are strengthening towards the Rennes basin, Auvergne and the east of Ile- from France to the Grand-Est.