Cold, general frost and snow on the plains: the weather forecast for this week
Through Brian Trebert
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After a very mild start to January, temperatures plummeted. And as anticipated since last week, the cold snap is here to stay. But it is the night of Wednesday 25 January to Thursday 26 January 2023 and Thursday morning that is of concern to forecasters, with risks snow on the plainsin most of northern France.
After last week’s sequence of three depressions (Gérard, Fien, then Hannelore), “the first anticyclonic cell, centered in northern Poland, developed a northeastern flow over France this weekend which maintained these cold temperatures we observed earlier in the week”, explaining to news.fr Meteorologist Yann Amice.
Then, “it is an anticyclone at over 1040 hectopascals which will gradually center between Ireland and the Azores in the middle of the week” and still supports this (cold) flow from north to northeast over France.
The wind accentuated this cold feeling
On the weather menu since this weekend, it’s generally calm and dry, with widespread frost and highs that rarely exceed 5°C in northern France. And the wind that brings out this cold feeling.
Therefore, winter conditions will continue this week, but special attention will be paid to the Wednesday evening through Thursday and Thursday morning 26 January 2023. Météo France is already anticipating “sleet or freezing rain”, unable, at this time, to target areas those most affected precisely.
During the night from Wednesday to Thursday, not only should a depression flow through northwestern France in this frigid air, but a thalweg, a small, low-pressure fuse that will circulate on the shores of this vast ocean. anticlone.
2 to 3 centimeters thick layer of snow?
“Maybe light rainfall, but it will arrive with cold air,” he continued. A snow cover of 2 to 3 centimeters is possible north of the Loire, in the late evening from Wednesday 25 January to Thursday 26 January, “between Paris, Reims and Orléans, according to weather models”, commented meteorologists .
“Predicting snow on the plains is always difficult when the temperature is around 0°C because water can easily and quickly change from liquid to solid and vice versa,” emphasizes Météo France.
“When it snows on the plains in France, the temperature on the ground is, indeed, most often between -5°C and +1°C. But snow can also fall, less often, with quite pronounced positive temperatures: it forms at high altitudes and develops in the air masses it encounters during the fall, ”explains the official meteorological and climatological service in France.
And let’s not forget the isothermal phenomenon that naturally lowers temperature when the first rainfall occurs, “these are the factors that often explain the appearance of snow when models see 1 or 2°C”, Yann Amice emphasizes:
Temperatures are about 4°C below the seasonal average
What seems certain at this deadline is that the high (and therefore cold) pressure will continue to exert its influence this week (with the exception of the Alps and Corsica on the Italian border) and perhaps at least into the weekend of January 28 and 29.
On the program: low temperatures, about 4°C below the seasonal average with frequent and sometimes severe snow, but not necessarily a chill. For such an episode to be identified on a national scale, the national average temperature must fall for at least one day below a certain threshold (-2°C). This week, January 22, the national thermal indicator is 0.7°C.
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