The cold and snow are currently expected in the mountains. And for good reason, the Christmas holidays begin on the evening of Friday December 20, with many of you heading to the mountain resorts. Good news, a good shot of white gold is expected across all the massifs at the end of the week, at increasingly lower altitudes. Thus, snowflakes could appear at very low altitudes, or even in the plains next week.
Establishment of a cold and initially humid regime
The synoptic configuration (on a large scale) will quickly change at the end of the week. A powerful anticyclone (>1040 hPa) will build up over the Atlantic and push towards Iceland and Greenland. This weather regime is technically called the “AR regime” for “Atlantic Ridge” in English meaning “Atlantic ridge”. This weather regime is conducive to a maritime polar flow, therefore cold and humid in our regions.
Cold setup next week © LCM
In this context, temperatures will drop suddenly from Sunday, with a deficit of -3 to -4°C nationally by the start of next week. The depressions will circulate over Eastern Europe, generating humidity, and therefore fairly heavy precipitation across all of the eastern reliefs.
Subsequently, at the start of next week, the flow will be oriented to the northeast sector, therefore even colder, but less humid, because the winds would no longer pass over the seas. This is commonly called the “continental flow”. This is when the rain-snow line could drop almost to the plain, with an even colder air mass.
Risk of showers in the plains in the northeast from Monday
It is therefore when the flow passes to the north-eastern sector that the risk of snow in the plains will increase from Monday. The precipitation will remain quite disparate, and this snow will fall in the form of showers or sleet. With slightly positive temperatures during the day, this snow will melt easily, but could hold from the first heights such as on the Lorraine plateaus (at 300-400 m), or even on the Morvan massif.
Overall, snow on the plains cannot be ruled out, but it seems limited with difficult ground hold due to the unmet thermal conditions.
Risk of snow © LCM
The regions most at risk are obviously the northeast, but also the center-east, where due to a return from the east and occlusion, snow could fall even in the towns in the valley.
Subsequently, this cold situation should last a few days, but in a drier and anticyclonic atmosphere, before the return of slightly milder conditions expected after mid-December. The Weather Channel is carefully following the evolution of the longer-term forecast, with a view to the end-of-year holidays.
