Yesterday we encountered more sun than expected in the northern Alps with a hefty layer of fresh snow. Locally, some 40 to 50 centimetres fell on the northern side of the Alps (southern Germany), but also other regions got fresh snow. Today it is the turn of the south-eastern Alps and Piedmont. Both regions could see very heavy snowfall.
Part two of PA#5: a lot of snow is falling in the Southeast Alps today. The low-pressure area over the Adriatic Sea is responsible for this flow. Until tomorrow afternoon, half a metre of snow will fall in Karawanken and Koralpe, among others. Locally, up to a metre of snow may fall. There are not many ski resorts in these regions, but Petzen and Koralpe, among others, will get a lot! Ski resorts such as Nassfeld, but also the Dolomites, however, will benefit well with some 20 to 30 centimetres.
The winds will pick up with this snowfall in the Southeast Alps. Especially higher up, it can really get quite heavy and most of the fallen snow will be moved again. Wind speeds above 120 km/h will occur. Also on the northern side of the Alps, these strong easterly winds will be noticeable. So watch out for avalanche danger! Slightly milder air will also move in with the south-easterly flow, allowing the snowline to rise to around 800 to 1,000 metres, but where the wind is slightly weaker it may also continue to snow down into the valleys.
On Friday, I already wrote about the snowfall in Piedmont. During the day, the core of the low pressure area moves from the Adriatic Sea to the Gulf of Genoa. Over the Po Plain, the flow turns to the east, which means that a retour d'Est could bring a lot of snow to Piedmont. The main snowfall will be for the areas south of (and including) Via Lattea. Think Prali, Limone Piemonte, among others. Note that there is not everywhere a proper base here.
It was not certain exactly how much would fall, but the calculated snow amounts increased over the weekend. Snow will follow in this corner in two phases: firstly today until tomorrow afternoon and then also on Wednesday. On a large scale, half a metre of snow could fall, locally even 70-100 centimetres is not out of the question either. Of course, some French areas such as the Queyras also pick up very well, as always with a retour d'Est.
In the northern Alps, things are a lot calmer. Here we encounter dry conditions with a mix of a fairly dense cloud deck and occasional sunshine. On Wednesday in particular, it will clear up significantly. Early this week, the core of the high pressure area lies just north of the Alps. Later this week, this high-pressure bridge between the Azorean high and the high-pressure area over Russia weakens and snow is again possible in the Northern Alps. In the current calculations of the American model, the high pressure area west of the Alps is too far west, causing the snowfall to pass the Alps and then provide some snow in the Pyrenees. So this snowfall is not yet completely certain.
Early next week another interesting situation could arise which could possibly produce a proper Nordstau, but this still depends somewhat on the location of the high pressure area. If it shifts too far to the east, the party will not happen. Again, there are still differences in the models. The ECMWF shows the snowfall mainly for Austria, but the GFS also temporarily has a northwestern component in it, allowing Switzerland to benefit more as well. We'll keep an eye on it!