WeatherBlog 4 2022/23 | Borderline weather situation, milder with Föhn in the next few days

Danger of black ice

With clear skies, low temperatures and generally calm weather, temperature inversions have formed over the last few days. "Lakes" of cold air lie in the valleys, while warmer air flows in at higher altitudes. In the northern foothills of the Alps in particular, this is currently leading to an explosive icy situation: a small disturbance embedded in the generally westerly flow is bringing some precipitation to the northern slopes of the Alps. This precipitation starts as snow in the higher atmospheric layers, but then falls through warmer areas and turns into rain. It becomes dangerous when the rain then falls into the still existing cold air lakes and immediately freezes on the cold ground. In addition to black ice on the roads, freezing rain can also become a problem for trees and power lines in extreme cases. The DWD has more information on the subject if anyone wants to read on and see a vertical temperature profile with several zero degree limits. MeteoSwiss also offers something similar today.

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Current situation and outlook

Apart from the local black ice problem, the weather situation currently looks something like this: The aforementioned disturbance is approaching the Alps from the north and, as mentioned, is bringing some precipitation. A foehn system is building up from the south. These two players are battling for the upper hand today (Wednesday), and by tomorrow at the latest, the Föhn should have established itself more or less everywhere. On a larger scale, the Greenland block, which kept us busy last week and was partly responsible for the recent cold temperatures, is breaking up. The polar vortex is still out of round and far from a textbook winter vortex, but the flow over the Atlantic and Europe is still relatively zonal at the moment. A low off the coast of France is also getting involved and will turn the westerly current into a south-westerly current over the next few days.

For the weather, this means foehn storms in the susceptible regions, especially tomorrow, Thursday. On the southern slopes of the Alps, it will snow or rain tomorrow and on Friday out of the accumulation. The snow line will be higher than recently, with the most precipitation currently expected in the southeast. A cold front arriving from the northwest will also bring some snow to the north on Friday. Temperatures are expected to remain lower here and the snow will probably at least make it to the higher valleys, but not much will accumulate.

The weather will calm down at the weekend. By Saturday at the latest, the precipitation is likely to subside everywhere and sunny, mild mountain weather will set in. The forecast also indicates fairly mild, partly cloudy weather for the next week. In the given constellation, one could hope for some snow at high altitudes. For the lowlands, it looks more like a mixture of sunshine and cloudy, dull weather than a winter wonderland. As is typical of a crystal ball, there is some potential for surprises, so perhaps the tide will turn towards a more wintry side.

LH

Winter mood, but without snow cannons it will be scarce.

Snow conditions

Well, that's about it. The SLF has modernized the snow depth maps and now offers a kind of "PowderMap" in which you can zoom around and switch between fresh snow, snow depth, relative snow depth (percentage of the long-term average) and other layers, as well as between two different lake levels. Unsurprisingly, the absolute and relative snow depths are not very pleasing at the moment and are well below average, especially at high altitudes. However, we do of course appreciate the new maps and congratulate you on the successful presentation!

Depending on the region, there is still barely enough snow for off-piste adventures, but the thin snow cover has already caused some unpleasant problems. The warning services have now gone into operation and are warning of weak layers in the old snow and constantly forming new drift snow. We are hoping for an improvement in the medium and long term, although it doesn't look like it in the short term!