The mid-winter conditions of the past few days are over. Check out Arjen's wonderful live report from St. Anton. Winter is retreating back to the high alpine regions. Especially the Northwest Alps are going to have some rough days starting Thursday with lots of snow, stormy winds and a high snowline. Only on Saturday, the snowline will temporarily be lower again, but most of the precipitation will have fallen by then. Locally, more than a meter of snow could fall, but especially for Friday and Saturday's snowfall, the weather models are still a bit inconsistent.
Today a rain area will pass north of the Alps. The northern areas will see a bit of rain and some snow above 1800 meters, but it won't be much. Tomorrow will start out sunny in many places, but during the day more and more stack clouds might develop. The wind will turn to the west and will pick up. Especially between the French Northern Alps and the Salzburgerland region, the clouds may develop into showers. From tomorrow evening on, there will be precipitation on a larger scale on the northern side. Until Thursday morning, the amounts will be about 5 to 15 centimetres above 1600 to 1800 metres. Most of it will fall in the French Northern Alps and Switzerland.
On Thursday, much more precipitation will follow from the west. The driving force is the strong jet stream just north of the Alps and a strong depression over the North Sea. While the French Northern Alps and the west of Switzerland have been covered in precipitation since the morning, Austria will most likely remain dry until the end of the afternoon. Here, the sun may even shine a little before the cloud cover becomes increasingly dense in the course of the afternoon.
To the north of the Alps there is considerably colder air than a few hundred kilometres further south. Precisely on the border of these two air masses there can be quite a bit of precipitation and the Northwest Alps will also benefit from this from Thursday evening, but some details are still uncertain. However, the Alps are just on the warm side of this border, so the snowline will still not drop. On the contrary, I expect the snowline to rise above 2000 meters in the night and Friday daytime. Until Thursday night, I expect accumulations of about 50 centimetres in the French Northern Alps.
On Friday, the next depression from the Atlantic will soon follow. With an eastern route over northern France and central Germany, this depression will also bring a lot of precipitation. During the day, it will continue to snow in the Northwest Alps above 2000 metres. Parts of Austria may have to deal with föhn for a while. In particular, the inner-Alpine areas east of Arlberg will remain mostly dry until Friday afternoon. In the evening, the cold front of this depression will follow, causing the snowline to drop quickly to well below 1500 metres.
On Saturday, the Alps are on the backside of the depression and therefore between high pressure to the west and low pressure to the east. This will give us a more northwesterly flow, which will also allow cooler air to enter and the snowline to drop further below 1000 metres. It will continue to snow all day Saturday in the form of (heavy) snow showers. From Sunday onwards, high pressure seems to take over temporarily, but with a new depression west of Europe over the Atlantic Ocean, this setting might also result in heavy föhn on the northern side early next week.
Up to Friday night, a metre of snow could fall above 2000 to 2200 meters in the French Northern Alps. Also the west of Switzerland will get a lot of snow, but further east, the uncertainty increases a bit because of the tricky snowfallevent on Friday. The models still calculate the course of the depression core in very different ways, which ultimately also has a big impact on the precipitation amounts in the Alps. According to the European model (with the core further north), only about 20 to 40 centimetres remain for the areas from Central Switzerland to the Arlberg and along the Alpine north edge. On Saturday, the ECMWF predicts an additional 10 to 15 centimetres in the northern and north-western stau areas, but these amounts will not come close to what will fall in the French Northern Alps.
The GFS also fluctuates a bit, but shows more precipitation for the rest of the northwestern Alps and Austria with more than half a meter for the northwestern areas. The GFS also shows larger precipitation amounts for Saturday than for example the ECMWF. The inner alpine areas of Tyrol and Salzburg will benefit less from this snowfall. With the exception of Saturday, there will be significantly less.
With the high snowline, you'll have to look higher up, but both Thursday and Friday, many lifts higher up the mountains will remain closed due to the strong storm. On Saturday the westerly wind will decrease a little bit, but still remains fairly strong. Only on Sunday the wind will really die down, but the avalanche danger will still be a problem due to the strong winds during Thursday to Saturday.
An update with more information about the snowfall will follow at the latest on Thursday. Hopefully I can provide some more clarity about the snowfall on Friday and Saturday!