DECRYPTION – The lowest temperatures in France in December since 2010 should give way to mild temperatures at the end of the weekend.
Until this Sunday morning, the populations of northern and eastern France will shiver. But “It’s pretty standard at this time of year”recalls Jérôme Lecou, forecasting engineer at Météo-France. “It is not exceptional, but this type of phenomenon is rarer at the beginning of winter, which begins on the 1is December from a meteorological point of viewadds Cyrille Duchesne, meteorologist at the Chaîne Météo (subsidiary of the group Le Figaro). There has been a temperature deficit of around 3°C since the beginning of December in France compared to seasonal norms. We have to go back to winter 2010 to find even lower temperatures during the month of December. “In Strasbourg, the temperature had dropped to – 18 ° C, against – 8 ° C this year, recalls Cyrille Duchesne. In Orly, it was -8°C, while this year it did not fall below
– 4 °C.»
Since the beginning of December, an anticyclone has settled over northern Europe and extended to the northeast of France. But because of cold air from Scandinavia, which on Tuesday met a warmer air mass over the country, brought by a marked ocean current, snow and freezing rain are to be deplored on a band which extends from Brittany to Alsace via the Paris region. Significant temperature disparities were noted with the south-west of the country on Wednesday morning, where the mercury marked + 18 ° C in Biarritz while it froze in Nancy (- 2 ° C). “This strong contrast between the South-West and the North will continue on Thursday morning”, adds Cyrille Duchesne. In total, 21 departments were placed on Wednesday in “orange vigilance” by the Weather Channel, as by Météo-France. A decision which is explained by the risk of snow and freezing rain which should last until Thursday, especially in a northeast quarter of the country. Great caution is requested from the populations of the affected regions. Because the rain is said to be “supercooled”, that is to say that its temperature is negative and that the precipitation risks forming a film of ice when it falls on ground cooled by very cold air. In addition, on Thursday, snowfall of 5 to 10 centimeters is expected. Fortunately, from this Thursday, the precipitation should begin to evacuate towards the east of the country. The temperature should remain well below 0°C over northern France with “maybe a Saturday morning which is likely to be the coldest of the week”, predicts the Weather Channel expert. But as of Sunday afternoon, the thermometer, including in the east of the country, should return to positive values. It is even expected, next week, milder than seasonal temperatures.
Read alsoSnow: from Normandy to Lorraine, discover the images of France under the snowflakes
Experts also refer to a “significant cold episode” to characterize the weather of this week in France and not “a cold snap”. This last expression meets specific criteria: the average temperature must fall at least below 0°C for three consecutive days throughout the country and fall below -2°C for at least twenty -four hours. Matthieu Sorel, climatologist at Météo-France, specifies that the current average temperature is around 1°C during the day, an anomaly of around 5°C compared to normal. Over the last decade, such a temperature difference had only been noted “December 31, 2016, December 29, 2012 and December 12, 2014”, much less often than before. The current month is also less cold than December 2010, which was the tenth coldest month of December since 1900 in France, nine of which had all taken place before 1970. The current weather is simply rarer in the context of a warming climate.