Snow and ice are back this weekend, especially on the Isère mountains. The department of Isère is placed in orange vigilance by meteo France this Friday, April 1, shortly after a spring episode and temperatures above 20 degrees. “We will have to adapt to this kind of situation“, estimates on France Bleu Isère, meteorological engineer, and former head of the Center Météo-France of the Northern Alps.
First of all, what is the extent of this cold snap? How low are we going to go?
We will first have a snowy offensive, before the cold really sets in. It will freeze, probably Sunday morning, after the snowy episode that will end tomorrow afternoon. But the real cold offensive is expected on Monday morning, with drier air and therefore temperatures in the plains or in the cold lands which should drop to -3, sometimes -5 degrees, and also affect part of the valley. of the Rhone. This is where cultures are most sensitive.
What is this cold snap due to?
So, there was an air of polar origin which began to descend five or six days ago. The air which arrives on this Friday in Isère was located in the north of Finland and there was a cold flow, an offensive coming from the North Pole.
A few days ago, we had hot air from the Sahara with sand. There, it looks cold, polar. Is it normal for these temperature variations?
This winter offensive is not so exceptional for the season. This yo-yo is really typical of the climatic characteristics of the off-season and especially of this month of April. So the cold offensive is not completely out of the ordinary. It is a meteorological situation that occurs quite classically in the spring, every 2-3-4 years. Sadly, there was an even stronger one last year.
On the other hand, what is unusual are the previous 15 days when we saw temperatures above 20 degrees?
So yes, all this and in particular the very strong and legitimate concerns of farmers and especially arboriculturists stem from the fact that winters, year after year, are getting milder and therefore the advance of vegetation is significant. This means that a fairly strong frost at the beginning of April occurs on trees and on vegetation that has already started and which can be greatly weakened by this advance in the calendar.
If I can hear you Serge, do you have to get used to these spring episodes of frost?
Yes, unfortunately the strongest frost on Monday morning will be concomitant with the last part of the IPCC report, which talks about this climate change and which confirms that we will have to adapt to this kind of situation. The frost, in April, is classic and it doesn’t diminish that much. On the other hand, the very mild winter becomes recurrent. And the vegetation is now always ahead of the calendar that was codified in the last century.
We are expecting fairly significant snow accumulations in the mountains today. Should that hold?
So in Grenoble, maybe the soil will be bleached tomorrow morning, but there’s still not much to fear on the plain. On the other hand, we fear much more on cold lands, with probably ten centimeters. And then especially on the Chartreuse, the Vercors and perhaps Belledonne, with up to 20-25 cm around 1,000 meters and even 30-40 cm above 1,500 meters. The ski resorts will be happy!