Today, Tuesday, a so-called counter-current situation will develop during the course of the day. This will bring a lot of precipitation, especially during the night and tomorrow morning, mainly along the central and eastern Alps and in northern and central Grisons. In the event of heavy precipitation, the effect of the precipitation cooling during the course of the night into tomorrow, Wednesday, may cause it to snow further down than the air mass potentially allows. In the northern Alpine valleys, there may well be a white surprise down to low altitudes. At the same time, rain will fall on the Central Plateau with less precipitation intensity below around 600 to 800 meters, there will be no snow at the lowest altitudes.
Snow all the way down, especially in central Switzerland!
Last night, the precipitation actually cooled down along the Alps and in some Alpine valleys, causing the snow line to drop down into the valleys and swiss plateau in places. There was particularly heavy precipitation in central Switzerland, where, with the exception of the Uri region, where there was not enough precipitation to cool down due to the slightly lower intensity, some wet snow fell in the valleys and lowlands (see Figs. 1 and 2).
Fig. 1: Snow this morning in Lucerne (440 m); Source: roundshot
Fig. 2: Snow this morning in Schenkon (580 m); Source: roundshot
However, the Bernese Oberland, Glarus and Zurich Oberland also saw a thin, wet blanket of fresh snow down to the lowest elevations in some places (see Fig. 3).
Fig. 3: A touch of snow this morning in Wetzikon (550 m); Source: roundshot
Contrary to most weather models, there was not enough snow at the lowest altitudes at the Walensee, in the Seez Valley and in the Rhine Valley, primarily due to insufficient precipitation intensity.
Looking at the precipitation map for the last 24 hours, there is a clear hotspot in Central Switzerland, the Bernese Oberland and Glarus (see Fig. 4). These are also precisely the regions where the snow line has been pushed down somewhat by the intensity of the precipitation.
Fig. 4: Precipitation total in the last 24 hours; Source: MeteoNews, UBIMET
In absolute figures, the Pilatus had by far the most precipitation in the last 24 hours with 81 mm. There were also two stations with over 40 mm and several with over 30 mm, most of which are located in the foothills of the Alps (see table below).
Amount of precipitation (as of 08:35)
| Measuring stations | Precipitation (in mm) |
|---|---|
| Pilatus (2106 a.s.l., LU) | 81 |
| Stöckalp (1070 a.s.l., OW) | 46 |
| Entlebuch (768 a.s.l., LU) | 42 |
| Grimsel (1980 a.s.l., BE) | 39 |
| Lucerne (456 a.s.l., LU) | 39 |
| Coldrerio (347 a.s.l., TI) | 35 |
| La Valsainte (1044 a.s.l., FR) | 33 |
| Engelberg (1035 a.s.l., OW) | 33 |
| Guttannen (1055 a.s.l., BE) | 33 |
| Elm (958 a.s.l., GL) | 32 |
| Adelboden (1353 a.s.l., BE) | 31 |
| Innerthal (903 a.s.l., SZ) | 30 |
| Kiental (930 a.s.l., BE) | 30 |
| Gersau (435 a.s.l., SZ) | 29 |
| Napf (1406 a.s.l., BE) | 29 |
| Brienz (566 a.s.l., BE) | 29 |
| Flühli (884 a.s.l., LU) | 28 |
| Langnau im Emmental (745 a.s.l., BE) | 27 |
| Meiringen (589 a.s.l., BE) | 27 |
| Bristen (784 a.s.l., UR) | 27 |
Lots of fresh snow, especially in the foothills of the Alps
In central Switzerland and the Bernese Oberland, there was locally more than half a meter of fresh snow above around 1000 meters with an avalanche danger of level 3 (considerable), as almost everywhere in the Alps. In the last 24 hours, 50 centimetres of fresh snow were measured in Guttannen, 49 centimetres in Adelboden and 47 centimetres in Gadmen. Larger amounts of fresh snow of up to half a meter locally also fell in the Glarnerland and in the southern Maloja region (see Fig. 5, for current measurements see here).
Fig. 5: Snowfall in the last 24 hours; Source: MeteoNews, UBIMET
In line with the large amount of fresh snow, the webcams are currently showing wonderful deep winter images in the mountains, especially in the foothills of the Alps, even at medium altitudes where the snow has been gone for some time (see Fig. 6 and 7).
Fig. 6: Snow this morning in Wengen in the Bernese Oberland (1250 m); Source: roundshot
Fig. 7: Snow this morning on the Wolzenalp (1100 m); Source: roundshot
Further developments today
In the morning, further precipitation will fall, especially along the Alps and in the east, with some flakes down to low altitudes; in the eastern swiss plateau, the snow line will be around 600 to 700 meters. In the afternoon, there will still be precipitation with a slightly decreasing intensity, especially in central and eastern Switzerland, with snow mostly from 600 to 800 meters, but it will slowly dry out here too during the night into Thursday.
How long will the snow cover last?
At low altitudes, the white splendor will melt away quickly and the snow will be gone everywhere by tomorrow. With the rather mild temperatures that will continue for the time being and foehn winds in the Alpine valleys from Friday to Sunday, the snow will also disappear relatively quickly at medium altitudes up to well over 1000 meters. The saying "March snow doesn't hurt" proves to be true.
Today and tomorrow will be used as examples to discuss the so-called counter-current situation, a very exciting weather situation that is difficult to assess, especially with regard to the snow line.
Counter-current situation?
Today, Tuesday, a high-altitude low is moving just west of our country from north to south, resulting in southerly winds at high altitudes. At the same time, an Italian low will develop during the course of the day, resulting in a northerly flow at low altitudes over the Alps. Fig. 1 shows the pressure pattern tomorrow night (Wednesday) at an altitude of around 5500 meters with the high-altitude low over France, Fig. 2 the corresponding wind conditions at this altitude and Fig. 3 the wind conditions at around 1500 meters.
Fig. 1: Pressure pattern and temperatures at 500 hPa, i.e. at around 5500 meters in the night to tomorrow Wednesday according to the European weather model ECMWF; Source: MeteoNews, UBIMET
Fig. 2: Wind conditions at 500 hPa, i.e. at around 5500 meters in the night to tomorrow Wednesday according to the European weather model ECMWF; Source: MeteoNews, UBIMET
Fig. 3: Wind conditions at 850 hPa, i.e. at around 1500 meters in the night to tomorrow Wednesday according to the European weather model ECMWF; Source: MeteoNews, UBIMET
You can see that the winds at altitude and near the ground are blowing from practically opposite directions; this is referred to as a counter-current situation. This can also be seen if you look at the wind conditions in the altitude profile in Zurich on Wednesday night (see Fig. 4).
Fig. 4: Calculated temperature and wind conditions in the altitude profile on Wednesday night in Zurich; Source: MeteoNews, UBIMET
Heavy precipitation along the Alps
In this weather situation, the northern side of the Alps is flooded with cold air from the northwest, while at the same time humid sea air is brought over the Alps from the south. As the cold air is heavier than the air flowing in from the south, the latter slides up over the cool air. This upward glide causes uplift processes and heavy precipitation. In addition, there is also a damming effect in the foothills of the Alps with northerly winds in deep layers of air, forcing the air to rise even more. This results in heavy precipitation, particularly along the Alps, which becomes heavier the further east you are (see Fig. 5). The heaviest precipitation is expected between around midday today and midday tomorrow.
Fig. 5: Precipitation total from around noon today until noon tomorrow; Source: MeteoNews, UBIMET
From the Bernese Oberland across central Switzerland to eastern Switzerland and in large parts of Graubünden, between just under 30 and over 40 liters of precipitation per square metre are expected in many places. The snow line will drop from 1000 meters and just over this afternoon to 600 to 800 meters tomorrow morning. This will result in around 30 to 50 centimetres of fresh snow in many places in the mountains.
Precipitation cooling with snow in the valleys?
With the expected heavy precipitation in the foothills of the Alps and in the northern valleys of Graubünden, the so-called precipitation cooling effect may set in (see Fig. 6).
Fig. 6: Precipitation cooling during heavy rainfall; Source: MeteoNews
During precipitation cooling, melting snowflakes extract energy from the surrounding air, which cools the air and lowers the snow line. In extreme cases, the snow line can be up to 1000 meters lower than calculated, especially in the Alpine valleys. The following factors are decisive for this:
- Persistent and heavy precipitation (as a rule of thumb at least 2 mm per hour) with a zero degree line around or below the ridge level of the Alps
- Low wind conditions so that the wind does not displace the cooled air
- Narrow valley locations, as considerably less air needs to be cooled here than, for example, over the same area on the Swiss Plateau. The narrower the valley, the more effective the precipitation cooling
The wind could become a problem if it snows right down to the northern Alpine valleys, as some wind from northerly directions is always to be expected with rising air pressure conditions, which ensures a certain amount of mixing. The question is whether the effect of precipitation cooling is stronger than the effect of mixing. This question cannot be answered conclusively, so it will only become clear tomorrow whether it will really snow down to the valleys.
Slow calming on Wednesday afternoon
In any case, the countercurrent situation will slowly ease during the day tomorrow, Wednesday, and the high winds will turn to the east. The damming effect will also slowly weaken, so that the precipitation will also slowly subside along the Alps in the afternoon. It is also possible that the snow line, which previously fell in the valleys, will rise again slightly during the day tomorrow as the mixing improves. In any case, it will be exciting in terms of snow as far as the northern Alpine valleys during the night and tomorrow, Wednesday...
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