Once again, the weather models had some trouble with the amounts and hotspots of this expected snowfall, but today a lot more details are known. After a mediocre second half of November, we will dive into winter in the first days of December with a good amount of snow in the southern Alps! Time for Powder Alert number 1!
In this weather report:
Before that, we see a divided weather pattern in the Alps today. While the western Alps are seeing a sun-drenched day, it is significantly cloudier in the eastern Alps. With a south-easterly flow, some snow showers pass over here. West of the Tyrol - Brenta Dolomites line it will remain pretty much dry. To the east, 1 to 5 centimetres of snow may fall. In the southeastern Alps, it may snow into many valleys, the snow reaching the alpine main ridge and north side of Austria falling to around 800 to 1000 metres. Just in the evening, some snow showers follow for the western half of the Italian Alps, a precursor to Saturday's snowfall.
The surface weather maps do not show a strong low pressure area which is often responsible for snowfall on the southern side, but looking higher up, we see a upper level low moving southwards over France. The axis of this trough higher up rotates counterclockwise. Long story short: in front of this trough, we see a strengthened south-easterly flow towards the southern Alps. Along the way, this flow has picked up quite a bit of moist over the Mediterranean Sea, so we can expect quite some snow from tomorrow.
First of all, it will be the turn of the Alpes-Maritimes on Saturday. In areas like Isola 2000, Mondolé Ski and Limone Piemonte, around 30 to 40 centimetres and maybe locally up to half a metre of snow could fall. Snow initially falls to (locally possibly even well below) 1,000 metres, but during the course of the day the snowline rises by several hundred metres. Winds also increase in strength on Saturday with the snowfall.
On Saturday afternoon and evening, the precipitation on the southern side of the Alps spreads further and further eastwards, but it also starts snowing in more and more places in the remaining parts of the French southern Alps. On Sunday, all regions in the southern Alps still benefit from the snowfall, with possibly 20 to 40 centimetres up to the Écrins. All in all, Ticino and the northern regions of Piedmont look set to benefit the most. In this convergence zone (read the definition of it in the article about southstau), some 50 to 70 centimetres could fall until Monday afternoon, with local outliers well possible. In the regions east towards the Brenta Dolomites, the amounts decrease again, by around 20 to 30 centimetres. For the Dolomites, Osttirol, the Carnic and Julian Alps, the amounts are still somewhat uncertain. The European model foresees a picture we also see in our weather model, with 20 to 50 centimetres of snow. However, the US model and the Mitteleuropa Super HD model by Kachelmann are still a bit more cautious in these regions. Still, I think 20 to 30 centimetres will definitely be possible.
As the flow turns a little to the southwest instead of southeast, we also see some more snow for the French northern Alps during the afternoon. It will remain at around 5-10 centimetres of snow for now. This snowfall could possibly move eastwards on the northern side of the Alps during the night to Monday and during the day on Monday as a result of colder air moving in, but this is not yet certain and I do not expect much more than 5 centimetres here anyway. Based on today's weather maps, I don't think we need to count on snow in the Northern Alps.
A side note on the snowfall for the southern Alps is that with this south-easterly flow, increasingly milder air is being transported into the Alps, as you can see above from the temperature at around 1,500 metres altitude. Due to precipitation cooling, it can continue snowing for a surprisingly long time, especially in narrow and deep valleys, with a low snowline, but in more and more places we will really see a gradually rising snowline. At the beginning of the snowfall, the snowline is mostly still well below 1,000 metres, but especially in the areas at the southern alpine edge, we will see the snowline rise to around 1,500 metres.
It is still very early in the season, so caution is advised. Even higher up, the snow cover is still quite thin or even non-existent in some places. Lower down, the first snow can also cause problems in the form of glide-snow avalanches. So keep a close eye on the avalanche reports.
Many ski areas are still closed, so if you want to enjoy the powder it will be touring in most places. Check our forecast for snow forecasts per area. Monte Rosa has been open since today! At the moment still with just a few lifts, but more will follow soon. Saturday is still too early for powder, Sunday there is already some possible (though with poor visibility), but on Monday the sun may come through in more and more places.
In addition, there may be some areas that could spontaneously open some lifts. San Domenico says it will open on Tuesday 6 December, immediately after the snowfall. Nassfeld, as mentioned, may also get a nice layer of snow and here it has been snowing quite a bit recently. Tuesday looks to be a brilliant day here too, but the season start here is not until Wednesday (7 December).
After Monday, things temporarily calm down again due to an intermediate high, but from Wednesday onwards we can already expect some new snow again. At the moment, the French Alps and Piedmont seem to be in the line of fire again, but details are still very uncertain! More on this in a next weather report.