Weather: snowfall in plain this Thursday, 3 departments on alert



COLD – The "cold snap" announced a few days ago is confirmed with temperatures well below normal season. At the same time, the snow will fall to lower and lower altitudes and eventually even touch the plains of the center-east. Three departments were placed on alert. Here are the (winter) forecasts for the weekend.

After the passage of a rainy disturbance in the night from Wednesday to Thursday, polar air will invade the country by the northern regions. At the same time, a depression will widen in the Mediterranean, bringing stormy rains to Provence-Alpes-Côte d'Azur. These same rains will win the Auvergne-Rhône-Alpes region in the afternoon of Thursday. It is at this point that the snow will replace the rain from 300 meters and punctually to the plain, leaving fears of disturbances on the road network of the region. Meteo-France describes this degradation as the 1st "significant snowfall of the season" and already places the Drôme, Isere and Ain in orange vigilance snow-ice.

Isere, department most affected by snow

If so far, snowfall has occurred at altitude, the situation will change from Thursday afternoon. The rainy disturbance will settle in the east and will be replenished by other rains from the Mediterranean. As the day progresses, the snow-and-snow limit will drop to around 300 meters. With this marked rainfall, a phenomenon of "isothermal" is also expected: the cold air at altitude is driven by the rains to the ground when they are intense and the snowfall then replace them to the plain. It is in the department of Isere that they should be the most intense with 5 cm expected in the streets of Grenoble, 10 to 15 cm in the region of Voiron (north of the department) and 20 to 30 cm expected from 500 meters. In the mountains, accumulations can reach 50 cm in the Vercors, Oisans and Bugey massifs.

This snow looks wet and sticky. Thus, it will bring a significant weight on trees and electrical cables in the region, raising fears of power cuts and disruptions on train traffic. Likewise, difficulties are to be expected on secondary roads and highways such as A48 or A43. These snowfalls will continue throughout the evening of Thursday and much of the night, also touching the Massif Central from 400 m. The region of Saint-Etienne and Lyonnais could also see the snow fall but it should not stand on the ground due to slightly positive temperatures.

Heavy rains in the southeast, January temperatures

In addition to snow, rainfall totals will also be monitored in the southeast. Heavy rain is expected in the late afternoon and evening of Thursday. The Var and the Alpes-Maritimes will be the most affected departments with thunderstorms, sometimes marked, and will be accompanied by intense rainfall, leaving fears of runoff in urbanized areas. During the episode, the expected quantities may occasionally exceed 100 mm, the equivalent of a month of rain in just a few hours.

This degradation will be accompanied by a drop in temperatures that will be worthy of January in most regions. Friday afternoon, the maximum will not exceed 2 ° C in Strasbourg and Grenoble, 4 in Lyon, 5 in Lille and Paris, 6 in Nantes or 7 ° C in Bordeaux. Sensitive north wind and showers will accentuate the cold feeling before the rise in mercury expected early next week.

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