Interesting developments await us for next week. First, a cold outbreak from the northwest will follow early next week and then the zonal jet stream shoots one low-pressure system after another towards Europe. In particular, the higher parts of the north-western Alps look set to take full advantage of this.
It is only the end of September and we can already get ready for a second round of snowfall. In the previous snowfall, the western and southern Alps got almost nothing with only a few centimetres in the high mountains. By far the most snow fell in Austria and especially in the north-eastern regions. We can clearly see this difference on a satellite image from the Alps.
The first event left locally up to half a meter of snow with snow falling even all the way down into the some higher valleys of Austria. In the inneralpine areas we didn't see more than 5 to 30 centimetres. It produced stunning pictures like the one below in Lech, but of course, by now much of the snow has disappeared again. Don't forget: it's still only September!
Yet the snow in the Eastern Alps is still holding out for a surprisingly long time. This is due to the high-pressure influence and weak northern flow currently prevailing here. We have had a few (for September) really cold nights with night frost reaching many valleys. We do not really find these cold air masses in the Western Alps at the moment, here it is milder, especially higher up.
This mild air will spread over the Alps today, pushing the cold further east. Due to an approaching depression, clouds are also increasing from the west. In the Eastern Alps, it will remain sunny today. The depression could cause quite a bit of precipitation in the regions south of the Po Valley, partly due to the warm Mediterranean Sea. In the Alps, some precipitation will also follow from the west on Saturday, but amounts will remain limited. After light föhn conditions, the precipitation will also extend further towards the Eastern Alps on Sunday. Here on the north side, the snowline may eventually drop to around 2200 metres due to incoming cooler air.
Things start to get really interesting after the weekend. A strong high-pressure core west of Europe and an approaching low-pressure area from Greenland towards the North Sea will create a slide of cold air that will reach the Alps on Tuesday. It is not yet certain how much snow this cold outbreak will bring. The European model shows 20 to 30 centimeters of snow possible for the north-western Alps, but the GFS is still somewhat cautious. What is certain, however, is that the cold will cause a sharply falling snowline to around 1,500 metres (and temporarily on the north side even a little lower).
In the following days, the wind turns more to the west and things could really get going. The jet stream has a more zonal pattern which causes depression after depression to be shot towards Europe. As a result, a lot of snow could start falling in the Western Alps. Precise details are still tricky because the models still differ (considerably), but keep in mind that the snowline will rise again (and may swab considerably in between). More info on these interesting developments in a new weather report after the weekend.