Have the inhabitants of eastern France just returned to the harsh winter? “Totally Siberian” temperatures were observed during the night from Friday to Saturday in Haute-Savoie and Burgundy-Franche-Comté, several weather sites report.
At the Swiss border, temperatures fell to -31.1°C in La Brévine, indicates Météo Franc-comtoise. In Doubs, -28.1°C was recorded in Reculfoz, -27.4°C in La Chaux and -23.9°C in Chapelle-des-Bois, according to Météo Villes and La Chaîne Météo.
“Cold holes”
These temperatures, which are regularly observed at this time of year, are not anomalies. Because they were recorded in “cold holes”. These are places with a particular topography which capture the cold, located in valleys or deep valleys, around 1,000 meters above sea level, specifies La Chaîne Météo.
Cold air can accumulate there and temperatures drop drastically in certain weather conditions. “When we have nights with snow on the ground on the massifs and a mass of cold air as we currently have over the country and a clear sky, the cold areas will radiate, that is to say lose light. “energy during the night and this energy will escape towards the sky, so it will promote snowy ground and cold nights”, explains François Gouran, forecaster at Météo-France.
In these conditions, cold air “tends to slide and accumulate in the bowls” [les « trous à froid », NDLR]continues the forecaster. The accumulation of cold air then leads to a drop in temperatures in these places. “In these places, the minimum temperatures are very, very low but they rise dramatically when the hole is in the sun. At the Solaison sinkhole in Savoie, it was -33.1°C at 2:30 a.m. and when day broke, the temperature dropped to zero and they were even positive this afternoon,” explains Guillaume Séchet, meteorologist at Météo Villes.
Significant differences with inhabited areas
This accumulation of cold air is generally not felt by the population. “No one lives in a cold hole. These are meteorological curiosities but it is not at all the sign of a cold snap,” explains François Gouran. “It’s not representative. It’s a way of measuring radiation and how far it can go. No one must have experienced -30°C last night but there are people who experienced -20, -25°C in inhabited places,” adds Guillaume Séchet.
Météo-France, which places its weather stations close to the population, recorded on its network the lowest temperature of -23.6°C last night, in Pierrefontaine (Doubs). In the village of Mouthe, Météo-France recorded the temperature of -19°C, almost 10 degrees higher than in the cold hole in the hamlet of Reculfoz, although located nearby.
An expected warm spell
And if 30 departments in the North-East were placed on orange alert this Saturday for snow-ice, it is unlikely that polar temperatures will be recorded again next night. “There is a milder air mass invading the country with its freezing rain and tomorrow morning there will be no more frost anywhere. There will be a big change in temperature with a big warm-up in the air during the night,” indicates François Gouran.
