Yesterday, the Südföhn set several temperature records for Switzerland and Liechtenstein. With a strong wind in Vaduz it became no less than 21.9 degrees yesterday afternoon. Today is the last day with Südföhn and it gets very warm again. With a slightly weaker pressure gradient, increasing clouds from the west and the increasing concentration of Sahara sand in the air, it is very unlikely that it will get as warm as yesterday. Nevertheless, temperatures of 20 degrees Celsius are possible, especially in the Rhine valley. We will have to deal with this warm phase until Friday and in the Alps we have to deal with temperatures well above 15 degrees.
While today will be sunny again in the Eastern Alps, clouds in the Western Alps dominate due to a nearby depression over Spain. The precipitation area is also approaching the Western Alps, but it seems that large areas will remain dry. Only in the westernmost areas in the French Southern Alps it could temporarily snow above 2000 meters, but not more than about 5 centimeters.
Due to a strong low-pressure area over the Atlantic Ocean and an omega blockade over Central Europe, the Alps will remain in this southwestern current with very mild temperatures for the next few days. Apart from some high clouds, it will be sunny again everywhere in the Alps tomorrow. Until Thursday, little will change in this weather situation.
The high temperatures in recent days have caused the layer of Sahara sand that settled about two weeks ago to reappear. For example, on the webcam image of Serre Chevalier above, you can see that the layer of snow from the subsequent snowfall has now partially melted. In the coming days, Western Europe will also have increased concentrations of Sahara sand in the air. This will be visible during sunrise and sunset, which are extra colorful due to the dust in the air. Whether, just like two weeks ago, so much sand will be deposited on the snow cover again is unlikely, but also uncertain.
What you see in the image above is a vertical section from Tunisia (left) to the Norwegian Sea (right) with the blue (dry) and black (moist) hues as the relative humidity. The mountain range between 45 and 48 degrees is the Alps. It can be clearly seen that the entire column of air above this part of the Alps (the line Bergamo - Bregenz at about 10 degrees east longitude) is very dry. In addition, the declining lines of constant potential temperature on the north side of the Alps are a sign of the prevailing Südföhn. Air from higher layers is brought down and can heat up strongly. Maybe this chart is a bit too complex for now, so I'll look if I can get back to this in more detail in a separate blog with some background information.
From Friday it will be temporarily over with the warm high pressure weather. From the northwest, with the arrival of a cold front, cooler air flows out over the Alps. The amounts of snow and the corresponding snow line are still uncertain, but snow could possibly fall again above 1000 meters. I do not see a real change to changeable weather in the weather maps at the moment. More details will follow on Wednesday!
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