After a short but powerful powder alert in the far southeast part of the Alps, it is time for the northwestern Alps from now on. Snow accumulations of up to half a metre are expected. After the rain damage and a very warm period around New Year's Eve, this snowfall is very welcome. But beware, the wind will pick up and the avalanche risk will be high!
In this weather report:
Ordentlicher Schneenachschub für Kärnten: 60 cm sind es am Nassfeld geworden.— Manuel Oberhuber (@manu_bx) January 6, 2022
Foto: Christina Staffa, Facebook/Wetterlounge pic.twitter.com/HDWjd7QjKo
In a very short time, more than half a metre fell locally in the extreme south-eastern Alps, locally up to about 70 centimetres of snow. In Sella Nevea, for example, 66 centimetres fell within 24 hours. Yesterday it cleared already in the morning and the webcams in this part of the Alps were a feast for the eyes. The large amount of heavy snow in the valleys caused a lot of snow chaos in many places in Carinthia.
The Alps are currently dealing with very cold air masses. With a rather cloudless night in many places, the outgoing radiation could cause quite low minimum temperatures. This morning on the Glattalp in Switzerland, a well-known spot for extreme minima, a temperature of -28.2 degrees Celsius was measured. In Samedan (Engadin), the temperature also dropped below -25 degrees. In Austria it was also a fresh morning with temperatures below -10 degrees on a large scale, locally below -15.
On the satellite image above, you can see that a large part of the Alps is still dealing with sunny conditions, but the first high clouds are already entering Switzerland. Directly west of the Alps, you can see an impressive band of clouds, which is the occlusion front of a large low pressure system over the Atlantic Ocean. The mighty system (with an extremely low core pressure of 931 hPa yesterday) is going to determine the weather for the Alps in the coming days. The first snowfall due to the passage of the occlusion front is not really spectacular yet and will only bring a few centimetres of snow. The real stuff will follow right behind it.
A small trough intensifies and moves from northern France to the east and will bring the second phase of snow in the northwestern Alps tonight. This small-scale feature will cause a strong upward movement at the edge of the Alps, resulting in a fair amount of fresh snow in a short time. I'm not ruling out the possibility of some local surprises in the snow amounts with this setting. However, the wind will increase considerably when this precipitation passes.
As I mentioned in my last weather forecast, the Western and Northern Alps will also have to deal with temporarily somewhat higher temperatures and thus also with a somewhat higher snow line when the warm front passes on Saturday evening. The pressure gradient over the Alps will increase before the cold front arrives, bringing the northern side into a short-lived föhn situation. We don't have to fear a dramatic rise, but temporarily the snowline may rise to around 1300 metres at the Alpine edge where the air is well mixed due to the strong westerly flow. In the more sheltered narrow valleys, the cold can hold out better and I don't exclude that it can still snow for a long time with a low snowline.
In the course of Saturday, a separate low pressure core will develop over the British Isles around the occlusion point of the large front system of the low pressure area just south of Iceland. The associated front will again bring precipitation to the north-western Alps. The westerly winds will pick up again as it passes through, making it possible for gusts to easily exceed 100 kilometres per hour in the high mountains, possibly even hurricane-force gusts. On Sunday, it can still snow throughout the day due to the stau, but in the night from Sunday to Monday it clears up everywhere with the exception of (the east of) Austria.
Monday will be mostly cold and sunny with increasing air pressure, which will also dampen the snowfall in Austria. In the eastern part of Austria it can still snow until the afternoon. From Tuesday, a fairly strong belt of high pressure develops from the Atlantic Ocean to Russia and directly over the Alps. Until the middle of next week, it looks like it will stay nice and cold, after that we might have to take into account some milder weather, but these developments remain uncertain for the time being.
The snowfall during the two snow phases will come more from the west, so the largest accumulations will be in the French Northern Alps. It is obvious that the Southern Alps will hardly benefit from this snowfall, but in Austria, too, they will hardly benefit due to the zonal direction. For almost all areas east of the Arlberg, I expect no more than 10 centimetres of snow, with most of it falling on the northern edge of the Alps. Only in the more exposed areas around the Dachstein and the Salzkammergut, more than 20 centimetres of snow could fall by Monday.
In terms of quantities, the models didn't really agree yet, so I kept a close eye on them in the past few days. The ECMWF shows up to half a meter of snow in the French Northern Alps until Monday, up to 40 centimeters in Central Switzerland and up to 20 centimeters in the Arlberg in the latest run. GFS is now also very similar to the European model. ICON and the Mitteleuropa Super HD of Kachelmannwetter are a bit more generous in the typical north-western stau areas up to the Glarus Alps. Our weather model even shows red colours on a large scale (over a metre of snow), but in none of the other models we see this. I still think that 40 to 50 centimetres in the stau areas in the French Northern Alps and the west of Switzerland is quite possible. Inner alpine amounts will be significantly lower.
As I said before, the wind is picking up during the snowfall, especially during the nights from Friday to Saturday and Saturday to Sunday. The rather large amounts of snow in combination with these strong wind gusts (>120 km/h possible!) will cause high avalanche danger. On Sunday, it will therefore not be possible in many places, especially in the high mountains, to safely make the first powder turns. Fresh wind slabs will be a widespread problem, so avoid getting into steep slopes or making your turns directly under steep slopes and do not leave the slopes without avalanche knowledge!
Sunday might still be a bit too early, especially considering the fact that especially the Western Alps have to deal with a stormy wind and it's still snowing so the aforementioned quantities will only be reached by Sunday evening. The avalanche risk is high higher up and many lifts will have to close and lower down there might not be enough snow for a deep powder day. Monday seems to be a better day. It's still cold and the sharp edges of the avalanche danger are (hopefully) removed, but keep an eye on the avalanche bulletins before you go out, because it will still be tricky! With the exception of Saturday evening, the snowline will be in the valleys pretty much the whole time, so look for it a bit lower. In the West and Northwest Alps, the base is still good almost everywhere (despite the recent warm period). Check among others: