From Friday until well into the coming week, the Alpine region will be subject to a strong northerly current, with the jet stream running right over the Alps. This northerly current will bring cold and intermittently moist air to the north side of the Alps and accumulate on the mountains. This will result in considerable amounts of fresh snow over several days!
No continuous northern alpine precipitation
Compared to yesterday's forecast, the course of events has changed somewhat, but this does little to change the wintry weather phase with a good portion of fresh snow. Our weather will still be dominated by a high pressure system today, but this will retreat to the Atlantic next night. Tomorrow morning, the north-westerly high-altitude current will bring a first cold front to the north side of the Alps and showers will spread.
Colder and colder air
The snow line will initially be around 1500 meters. With strong westerly winds, temperatures will reach 8 to 10 degrees. A second cold front will follow towards the evening, bringing much colder air with it. The snow line will fall below 1000 meters in the evening and then quickly drop to low levels during the night. On Saturday, new waves of cold and humid polar air will follow, which will accumulate along the Alps. Saturday will be cloudy and wintry here, with snow falling right down to the valley floor. However, there are often gusty winds and the ground is not frozen. The amount of fresh snow is therefore likely to be limited at low altitudes. In the Swiss Plateau, there will only be occasional snow or sleet showers anyway. On the mountains, however, there will be a considerable increase in fresh snow, as it will continue to snow on Sunday night.
Fig. 1: Weather on Friday – Repeated showers in the north, snow line dropping significantly in the evening; Source: MeteoNews
Intermediate high pressure
On Sunday itself, however, an intermediate high will extend from the west to Switzerland, the snow showers will retreat to the eastern northern slopes of the Alps and will also subside here during the day. The clouds will clear, and in French-speaking Switzerland it will even be quite sunny at times in the afternoon. In the south, the sun will dominate anyway under the protection of the Alps, with a northerly Foehn blowing in the valleys throughout the weekend. From Friday to Sunday afternoon, up to half a meter of fresh snow will fall on the mountains in the north, with up to one meter possible in some regions. However, the snow will be transported by the wind, forming treacherous accumulations of drifting snow – and increasing the risk of avalanches.
Fig. 2: 48-hour snowfall forecast until Sunday, November 26, 12 noon UTC ; Source: MeteoNews, Ubimet
Low over the English Channel
At the beginning of next week, we will be on the front side of a small low over the English Channel, with the associated warm front approaching. As a result, Monday will bring a lot of clouds again, but from today's perspective, a large part of the day will still be dry. However, this timing may well change! During the afternoon, or towards the evening at the latest, new precipitation will set in from the west. Initially, it may still snow down to lower altitudes, but the snow line will then rise somewhat, especially in the west. On Tuesday night, the low pressure system will move across France, Switzerland and Italy towards the Adriatic. On its backside, the upper-level current will turn north once again, bringing very cold polar air to us by Wednesday. The snow line will drop to low altitudes, but precipitation will also decrease as the coldest air arrives. The models are still somewhat divided as to exactly how cold this air mass will be.
Fig. 3: 48-hour precipitation amount until Wednesday 03 am UTC ; Source: MeteoNews, Ubimet
On Thursday, an intermediate high will probably have a temporary effect on the weather again. The unusually warm 2/3 of fall will come to an end with wintry temperatures!
Fig. 4: Outlook for the coming days; Source: MeteoNews
From Friday, the Bionda high pressure area will position itself over the Atlantic and western/north-western Europe. On the other side is a low pressure zone Niklas in eastern and north-eastern Europe. In between, the band of strong winds in the higher layers of the troposphere (lowest part of the atmosphere in which the weather takes place) – the jet stream – runs from north to south over the Alps (Fig. 1). The situation is blocked for several days, so that cold and intermittently moist air reaches the northern side of the Alps. The north wind also causes the moist air to accumulate on the mountains, forcing it to rise, which leads to an increase in precipitation.
Fig. 1: The jet stream will run exactly from north to south over the Alps from Friday until well into the coming week.; Source: MeteoNews / UBIMET
Lots of snow for the mountain regions
The weather conditions described above will result in exceptionally interesting snow conditions for the northern slopes of the Alps. Although enormous amounts of snow do not fall within a short period of time, the fact that snow falls repeatedly over several days means that there is still a large amount of new snow in total. The largest amounts of fresh snow are likely to fall between the Bernese Oberland, central Switzerland as far as the Alpstein and northern Grisons/Rätikon and further east over the Voralberg, Tyrol to the Hohe Tauern and the most localized foothills of the Alps. Although there are still some uncertainties in the models, there are many indications that the regions mentioned above 600 to 800 meters will see widespread 50 to 100 cm of fresh snow in an initial phase from Friday morning to Monday evening.
However, this will probably not be the end of the story. Snowfall is also likely to be the order of the day for the rest of the coming week. The risk of avalanches will increase massively – also because the snow at high altitudes will also be heavily displaced by the stormy north wind!
Little snow for the lowlands
While the mountains in the middle and higher altitudes will be heavily snowed in, there will be significantly less snow in the lowest altitudes of the valleys. Only modest amounts of snow are also expected on the Central Plateau, with a few centimetres at most, especially in the eastern Central Plateau.
The following maps illustrate the daily amounts of fresh snow from Friday to Monday for the entire Alpine region (Fig. 2 to 5) as well as the total accumulated amount of fresh snow from Friday morning to Monday evening for Switzerland and Austria (Fig. 6 and 7) with the forecast time at midday on Wednesday.
It should be explicitly pointed out once again that the last two maps do not simulate the snow depth on Monday. It is the accumulated amount of new snow over 4 days. Due to the heat still present in the ground, there are melting processes at low altitudes, for example, which cause the small amounts of fresh snow to melt again quickly, at least partially. In the mountains, the snow is also subject to a constant settling process. This means that the snow depth does not grow 1:1 with the amount of new snow that has fallen due to the weight of the large amounts of snow, because the snow cover is constantly being compressed.
New model maps and further assessments of the weather situation will follow here tomorrow.
Fig. 2: Expected amount of fresh snow on Friday, November 24, 2024; Source: MeteoNews/UBIMET
Fig. 3: Expected amount of fresh snow on Saturday, November 25, 2024; Source: MeteoNews/UBIMET
Fig. 4: Expected amount of fresh snow on Sunday, November 26, 2024; Source: MeteoNews/UBIMET
Fig. 5: Expected amount of fresh snow on Monday, November 27, 2024; Source: MeteoNews/UBIMET
Fig. 6: Fresh snow forecast for Switzerland from Friday morning to Monday evening; Source: MeteoNews/UBIMET
Fig. 7: Fresh snow forecast from Friday morning to Monday evening for Austria; Source: MeteoNews/UBIMET
The content of this article has been at least partially computer translated from another language. Therefore, grammatical errors or inaccuracies are possible. Please note that the original language version of the article should be considered authoritative.