On to a major deterioration of the weather in the south this weekend

Through Regis CREPET, meteorologist

While the continental height covers Europe and guarantees dry and sunny weather over France in this first half of the week, weather conditions in the Mediterranean will deteriorate significantly this weekend. Heavy rains and high winds will hit the Iberian Peninsula and, on the sidelines, possibly Languedoc-Roussillon and the Pyrenees. It will be a Mediterranean episode.

The meteorological situation is changing rapidly in France. After a start to the week marked by a short cold spell on the edge of the cold spell that is ruling Eastern Europe, the current is moving south and bringing mild air over our country. This development is favored by the retreat of the anticyclone and the approach of Atlantic depressions. But this situation will remain blocked for several days, probably until next week. The southerly current is therefore likely to cause intense rains around the Mediterranean, accompanied by winds from North Africa, with the prospect of sand showers over France.




Towards a risk of an episode from the Cevennes and the Mediterranean


The concept ofCevennes episode is usually attributed to autumn, when masses of mild and moist air, laden with heat, coming from the Mediterranean, pour intense rains in Languedoc-Roussillon, and in particular the Cevennes. When the episode expands to more regions, it will be referred to as:mediterranean episode


In front of this weekend, the different numerical models we use point to a possible episode of this type, associated with a very deep depression positioning itself in the Iberian Peninsula. This would then cause the winds to shift to the south-southeast sector across the Mediterranean, favoring the upwelling of heavy rains into the Gulf of Lion. At the moment and given the mobility of the depression, it would be difficult to make an accurate forecast of the expected precipitation accumulations, but on a global scale it seems that the departments stretching from the Pyrénées-Orientales to the Cévennes, as well as The eastern Corsica is exposed to this heavy rainfall, with a good agreement that the maximum intensities fall on the Cevennes. To date, the target accumulations for the two days of the weekend are estimated between 150 and 300 mm on the reliefs of the Cevennes, which still leaves a significant margin of error. But these accumulations are important. It should also be noted that this heavy precipitation d. would giveheavy snowfall heavy and humid in the Cevennes and the Eastern Pyrenees from an altitude of 1400 m.





An atypical situation for the season


The episodes of the Cevennes and the Mediterranean usually take place in the autumn. Some sometimes ignite in the spring, but rather in May, when thunderstorms begin to form. In March it remains rare. But if the centers of action are positioned to create a southerly current across the Mediterranean, an episode of the Cevennes is possible even in this season. In March this happens on average once a decade, the last series dates from March 2011 and March 2013 with accumulations of 150 to 200 mm in the Cevennes and Roussillon. In the past, the Cévennes had occasional rainfall in March 2004, 1999, 1996 and 1986, especially in March 1969 and 1971, when there was a lot of rain, but without exceeding 300 mm in two days. If this weekend’s episode were confirmed, the intensities would be remarkable for this time of year.




Threat of bad weather and flooding in the Iberian Peninsula


In this configuration, the Iberian Peninsula will also be exposed to heavy rainfall due to the positioning of the depression directly over Spain. After an exceptionally dry winter, these expected heavy rains are good news for filling dams that are sometimes nearly dry, but are at risk of flooding due to flow on paved soils. For this weekend, however, the accumulations will not be greater than in Languedoc-Roussillon, but strong storms will break out all over the territory, from Galicia to Andalusia via Portugal. For next week, while France could experience relative calm, heavy rains in Spain could continue until Wednesday, raising the risk of flooding.


Rain and sandstorms for the Maghreb countries


North Africa has been hit by notable rain showers since last weekend, especially in Morocco where the coast has sometimes fallen by more than 100mm, with lots of snow in the mountains from 1500m above sea level. Rains are more moderate in Algeria and the rising sirocco is likely to trigger a sandstorm this weekend. But there too, the highly disturbed episode could last much of next week, especially in Morocco, where flooding could also occur.