What are returns?

The temperate climate of France and Western Europe is controlled by prevailing winds from the Atlantic Ocean. In our hemisphere, especially due to the Coriolis force, currents from the west to the southwest prevail. Depending on the location of the centers of activity, this flow may reverse and turn eastward, lowering the disturbance from central Europe: then we speak ” return from the east “. This configuration is more common in winter, but can also occur in spring and early summer.

Mechanism related to the position of activity centers

In meteorology, the centers of motion define the anticyclones and depressions that control the direction of the winds: around the anticyclone, the wind rotates in a clockwise direction, and around the depressions in the opposite direction. In the classic meteorological configuration where the British Isles lows circulate and the Azores anticyclone is located, it is easy to follow the direction of the winds: they are directed from the west to the southwest sector.

The principle of eastern returns © Weather Channel

But these centers of activity are mobile, and it happens that depressions circulate further south, and anticyclones migrate north. This type of configuration then reverses the direction of these winds. This inversion is particularly noticeable in the Mediterranean, when a depression circulates between Corsica and northern Italy and an anticyclone is located over the British Isles or the North Sea. This context causes winds to be directed over the country to the Eastern sector. Disturbances from these depressions thus return from the east towards France, hence the name “return from the east”.

If the direct result of this type of configuration is an easterly direction of flow, the designation “return from the east” also indicates the presence of disturbance and therefore bad weather. This type of weather occurs mainly in winter and sometimes in spring: cold weather is accompanied by precipitation from the east, which explains the main characteristic of this type of situation, namely the arrival of snow up to the plains. One of the consequences of these returns from the east is the prevention of these disturbances in the Alps on the Italian side, which constitute the typical configuration of heavy snowfall in our massifs along the border from Mercantur to Queiras. The return from the east also refers to the eastern side of the Pyrenees facing the Mediterranean Sea.

snow on the plain

As a depression forms between northern Italy and Germany, unrest flows east-northeast back to France. The air from the continent is cold and snow may fall in the north-eastern half of the country and in the central-eastern plains. Snow remains light to moderate under low and gray skies, but remains on the ground as temperatures stay close to 0°C throughout the day.

On the other hand, because of the cloudy sky, the cold remains mild at night and the frost is weak. In November 2019, such a configuration caused Early heavy snow in the Rhone Valley, particularly in Valence (Drôme), where the weight of the snow broke power lines, leaving thousands of residents permanently without electricity. Similarly, a large snowfall episode in the lowland returning from the east occurred from 8 to 11 December 1990, with 69 cm in Amberier (Ain) and 50 cm in Lyon. On 8 March 2010, a return from the eastern Mediterranean caused a very heavy snowfall of 40 cm in Perpignan.

In the lowland regions of the northeast, snowy episodes associated with returns from the east are weaker and decrease towards western France, but snow may fall in Alsace and Lorraine.

Snow in the mountains: impressive thicknesses at the border of the Alps

It is in the east-facing range of the Alps that “returns from the east” are especially abundant. Cold and moist air masses rise up the Po plain and against the steep slopes of the Italian foothills, where they bring down heavy snow. In these cases, the massifs of Queyras, Mercantour, Ubaye and even east of Vanoise (Haute Maurienne), at medium altitudes as well as in Abries (1500 m) can encounter effective snow thicknesses of 70 cm to 2 m.

The open sectors are the sectors facing Italy where the concern comes, but the snowfall may penetrate a little to the west and reach the Briançon area and the eastern slope of the Lautaret pass (east of Ecrins). Since this situation occurs only two or three times during the winter, they are eagerly awaited by the respective winter sports resorts. When this happens, it is “snow packed” so that it often allows the season to be completely quiet. The sectors most affected are the Upper Alps, Abries, Saint-Véran and sometimes Montgenevre; Alpes-Maritimes, Isola 2000 and sometimes as far as Auron. Some resorts in Haute-Maurienne are concerned, such as Valfréjus in Savoie, Val Cenis, Bonneval-sur-Arc and Val d’Isère.

Greatest Returns from the East It happened in January 1978 (more than 3 m of snow in 3 days in Queiras in Ristolas). In January 1986, 1.60 m fell in 24 hours at Abries. Saint Veranda received 2 m of snow in December 2008 and 2 m of fresh snow in Bonneval-sur-Arc in January 2018.

The returns from the east bring the humidity of the Mediterranean Sea and, together with the cold, sometimes allow heavy snowfall down to the plains, especially in resorts such as Les Angles, Formiguères or even Font-Romeu. , with thicknesses that can reach 1-2 meters in a few days in these sectors, such as the Alps. These snows close the Capcir region and the exit to Andorra. One of the most exceptional episodes occurred on March 8, 2010.

Therefore, returns from the east are an opportunity for some exposed massifs to be filled with snow within a few days. If an episode occurs early in the season, which is possible from November, the respective stations are more confident of having a good winter season. For the plains, apart from the center-east and the Rhone corridor, the returns from the east do not produce any significant snowfall, with the heaviest generally remaining in northern Italy, Switzerland and Germany.

It snowed heavily on the way back from the east © Weather Channel

Summer returns from the east: showers

If the returns from the east are mainly cold season events, some occur in spring and very rarely in early spring: then there are showers. These rains remain blocked in the Alpine arc, causing floods and devastating floods. The amount of precipitation is such that it can cause flooding of the rivers descending from the Alpine arc: the Rhine on one side and the Danube on the other.

The most powerful floods of these rivers also occurred in the following cases: the flooding of the Rhine in May 1999 and the beginning of June 2013, and the flooding of the Danube in June 2013. When a depression directly exists over Germany and the Benelux, rains and thunderstorms are exceptional and dramatic flooding Mid-July 2021Where more than 150 victims were counted.