After weeks of dry and warm weather with a lack of snow in the Alps, it is finally time for some fresh snow. Unfortunately, it will still remain mainly dry for much of the Alps, but the Northern Alps will get a nice refresher with a cold front from the north on Friday evening. Just enough for a PA in these difficult times. More details PA#7 will follow in an update (Friday morning at latest).
In this weather report
Before we head to the Alps, I want to give a quick preview for the Pyrenees, because here we can expect quite a bit of fresh snow, especially tomorrow. Taking the weather map at about 5 kilometres altitude, we see that a strong high-pressure area over the Atlantic blocks things and a large trough reaches the Iberian Peninsula. Initially, it causes snow in the Picos d'Europa from tonight, but during the night a core over Spain causes winds in the Pyrenees to turn south and push up can take place.
Until Friday morning, half a metre of snow could fall, especially in the western half of the Pyrenees, higher up even possibly more. The snowline drops from around 1600 to 1000 metres during the snowfall. In the east, however, it will be milder and the snowline will remain at around 1400 metres. In Andorra and the areas east of it, for example, there will also be significantly less snow. Friday clears up early in the morning everywhere.
In the Western Alps, it started snowing this afternoon. It really only stays at a few centimetres with still a fairly high snowline of around 1600-1800 metres. Tonight, this precipitation will move further eastwards, weakening a bit. So it mainly ensures that the sun-drenched conditions are over again for a while, but for decent snowfall we still have to wait until the weekend.
Incidentally, west of the Alps, quite a bit of saharan dust is being transported northwards. This was already quite noticeable in the Pyrenees yesterday and visibility was also slightly reduced today in the French Alps. Tonight and overnight, we will also see these increased dust concentrations moving further east. However, it will not have a big impact like last March, but it may cause more cloudiness as the particles act as condensation nuclei, on which water vapour can condense.
Some showers may fall across the southern Alps and the northern Alpine rim on Friday. Again, it will not deliver much. In between, in the inner-Alpine areas on the northern side, it may clear up a lot better. This is because we temporarily see a larger air pressure gradient between the north and south sides, making it a bit föhny on the north side. Over the course of Friday evening, however, the cold front from the north will follow, clearing the föhn and also finally bringing snow to the northern Alps.
The centre of gravity seems to be in the northern stau areas between eastern Switzerland and Salzburg. The cold front will create a snowline that will rapidly drop to around 500-700 metres. In the cold air behind it, it could still snow during the day Saturday in the stau areas. Especially during the cold front passage, we have to reckon with strong north winds with stormy gusts higher up.
Higher up, some 20 to possibly 30 centimetres of snow could start falling. Just enough for a powder alert, especially as it will likely continue to snow during the day on Sunday. Due to increasing air pressure, this snowfall will get less strong during the day. Note that inner-Alpine areas like the Ötztal Alps may get significantly less. In the Zillertaler, Kitzbüheler Alps and the Western part of the Tauern, snowfall is more likely to get further south.
Despite increasing air pressure from the north, low pressure still remains present at high altitudes. Early next week, this bubble of cold air moves further towards the Iberian Peninsula. With low pressure building over the Mediterranean, there are possibilities for (quite some) snow in the Alps, but it is still far away to pinpoint the possible hotspots. Some model runs hint at a retour d'Est, others for snow across the southern Alps, but with Nordföhn and/or a slightly different flow, among others, this snowfall could also be stopped. In any case, these are interesting developments with finally some snow chances again, but as it is still far away we will wait and see.