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 at the beginning of next week.
Establishment of an Atlantic ridge regime
The synoptic configuration (on a large scale) will quickly change at the end of the week. A powerful anticyclone (>1050 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.
Polar flow © LCM
In this context, temperatures will drop quickly, 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, the flow would be oriented to the northeast sector, therefore still cold, but less humid, because the winds would no longer pass over the seas. This is when the rain-snow line could drop to the plain, with an even colder air mass.
Risk of showers in the plains in the northeast
It is therefore when the flow passes to the northeast sector that the risk of snow in the plains will increase, either Sunday or Monday. Precipitation will remain quite light a priori, 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).
Risk of snow in the plains © LCM
It is still difficult to give a probability range by region at this time, but the risk of seeing the snowflakes fall is not negligible in the northeast. Particularly between the Ardennes, Lorraine, Franche-Comté and Alsace.
Subsequently, this situation should not last with the return of slightly milder conditions. But another winter “offensive” is not impossible around December 15-16. The Weather Channel is carefully following the evolution of the longer-term forecast, with a view to the end-of-year holidays.
