The temperatures for your weekend are expected to be very cold with a risk of white frost. Is winter already upon us?
While thethe weather conditions were excessively hot since many weeks and even months, a change is taking place this weekend. The high pressures reinflate for this weekend and their positioning generates a much colder air supply altitude. Of the white frosts can even be invited in certain campaigns. But is it the early arrival of winter?
Although the mercury can dip very low especially in the plains Hauts-de-France as well as in the Grand-Est region, winter is not for tomorrow ! Indeed, with very low minimums for the season (count up to 1-2°C in open Champagne countryside) it is true that the feeling could be wintry but … these white frosts are not expected to be unprecedented in these regions, although this will be all the more surprising after a very hot summer season.
Count for example Sunday morning, 8°C near Lille and Strasbourg, 6°C in Verdun. Great freshness also towards Brittany with 6 to 7°C outside the coasts.
This the fall in values will be more marked at the level of the various massifs, including that of the Alps who should find negative temperatures. Nothing unusual however but the change in weather is noticeable compared to the past few weeks. To note some possible snowfall for the day on Saturday in the middle mountains on the Alpine massif.
How to explain the potential for white frost around mid-September?
L’flow orientation plays an important role in the supply of cooler or even cold air at altitude. These next few days, it will stay in the North/North-West allowing the arrival of a first descent of polar air (not as intense as in the middle of winter, don’t worry).
The presence of this air is not enough. It’s necessary look at the stability of the atmosphere. If conditions are disturbed with rainy and windy periods, a mixing of the air will be done strongly limiting the baisse mercury during the nights.
In the opposite case, as it is planned in particular for the days of Saturday and Sunday, we are in an area of high pressure : the atmosphere is stable and the wind is not very present favoring a decline in mercury.
In night course, pockets of clearings should resist over a wide North-East quarter : the infrared radiation from the Earth can therefore be easily evacuated altitude. This loss of heat near the ground will cause thermometers to drop noticeably in the sectors most sheltered from any turbulence. Of the white frosts can therefore be observed. It is moreover possible that in a very localized way, frosts under standardized shelters are observed the coming days.