After a weekend and a Monday marked by the return of heat, the weather situation will change over the next few hours with further deterioration expected, resulting in the outbreak of sometimes very rainy thunderstorms.
The weather is about to change once again, under the influence of a depression positioned in the vicinity of Portugal. Ahead, a southerly flow rose, bringing locally strong heat with peaks of up to 35 ° C in the Landes department on Monday afternoon. From now on, the weather will therefore change with the slow progression of this depression which will destabilize the air mass. Thunderstorms, which began to erupt in the west on Monday evening, will reach more and more regions while heavy rains are to be feared near the Cévennes.
On Tuesday, the risk of thunderstorms will gradually spread, from the western regions to the northeast. Although they will remain isolated most of the time, they can nevertheless turn out to be strong from time to time with intense rains bringing accumulations of the order of 10 to 15 mm in the space of a few minutes. In the evening, the most virulent cells will affect the center-east, from Auvergne to Alsace via Burgundy with there too, intense rainfall with significant accumulations over periods ranging from 15 to 30 minutes and the key, possible runoff.
Sometimes strong thunderstorms are expected over the next few hours. Sustained rains also in the direction of Gard, Hérault and Ardèche. #rains #floods #thunderstorms More maps: https://t.co/7XlsIEA2OI pic.twitter.com/pXT3m5XLOq
But it is especially on the night of Tuesday to Wednesday that it will be necessary to be attentive, and more particularly in the southwest where instability is expected to increase, generating a powerful thunderstorm. Approaching the Basque Country, it will then travel between eastern Aquitaine and western Occitanie then Limousin. In the morning, these heavy thunderstorms will affect Poitou-Charentes, the central regions and Burgundy before continuing their route north, while gradually easing. They will bring quantities often between 40 and 60 mm, or the equivalent of a month of rain which is however welcome after several weeks of generally dry weather in these regions.
The other area to watch closely is located in the south-east and more precisely near the Cévennes. A low pressure level will direct a south-easterly flow in the Mediterranean, thus bringing humidity to the Cevennes landforms. The risk of bad weather episodes is thus real between Tuesday and Thursday but with significant uncertainties between the forecast models, like the situation in the Aude last week with finally, an episode of heavy rain quite classic. For now, the risk of intense and long-lasting rains is fairly limited, but beware of possible stationary thunderstorms that could be a game-changer.
The first low intensity rains set in on the reliefs of Hérault and Gard on Monday evening. They will be maintained throughout the day on Tuesday as well as Wednesday. By evening, the situation is expected to worsen with powerful thunderstorms expected across Languedoc, including the plains, before gradually easing on Thursday. During this period, the accumulations will generally reach 40 to 60 mm, locally up to 100 mm on the relief. With such quantities, the risk of flooding therefore seems limited, but beware of locally possible stationary cells, as the Agen sector experienced last Wednesday. This is why it is important to carefully monitor the evolution of the forecasts on our site over the next few hours and days.