I have written enough about the expected rain with a high snowline and stormy westerly winds higher up in the past two weather reports. Today is the day, but I also want to comment on a possible bright spot and look ahead for the long term through to the end of the year. Can we expect some more snow, also for the lower areas?
It's a powerful westerly flow we are now dealing with. It became clear last night with recorded wind gusts of 146 km/h on the Hoher Kasten, 130 km/h on the Moleson, 113 km/h in Disentis and 111 km/h on the Corvatsch. Also this morning, we will see wind gusts of 80 to 120 km/h in many places. Especially during the afternoon, the winds will pick up again in strength considerably.
Today, the Alps are in the warm sector behind the heat front of a depression over the Atlantic. Higher up, we will get a lot of snow today as expected (locally around the Mont Blanc massif over a metre and on a large scale 50 to 80 centimetres in the high mountains of the Northwest Alps!), but in combination with the stormy winds, we can thus expect wind slabs which will be deposited on a weak old snow layer in large parts of the Northwest Alps. Avalanche danger will be very high! At 8am there will be an update of the avalanche danger map below on the website of slf.ch.
So this high snowline of around 2200 - 2500 metres in the west and up to 2000 metres on the north side is unavoidable, but a bright spot in this rain phase is that the cooler air from the north will push the snowline down a bit during the evening anyway, especially in the eastern regions of Switzerland and western Austria (Arlberg). Here, rain could turn back into snow around 1,500 metres (and possibly temporarily a little below). A side note here though is that the biggest precipitation amounts are already behind us as this cooler air moves in.
For powder, we will have to look considerably higher over the weekend, but even then it will still be stormy in the mountains (and don't forget the high avalanche risk!). Switzerland and western Austria will also have to reckon with remnants of snowfall tomorrow, which could still be quite heavy, especially in Switzerland with some 20 to 30 centimetres higher up in the stau areas. The snowline is still at 2,000 metres in the west and several hundred metres lower further east. On Sunday it will clear from the west and a new portion of warm air already reaches the Alps from the southwest. With föhn, temperatures in the northern and western Alps could reach around 8 to 10 degrees at 1500 metres.
The cooling we saw in the European model (which I mentioned on Wednesday) we now also see in the US model, but all in all the impact remains limited. Indeed, it will not be a prolonged cooling. After the weekend, we face a passing cold front from the northwest. The snowline drops from around 1,600 to 1,800 metres to 1,200 to 1,400 metres and possibly even a little lower during the night to Tuesday. From the French Northern Alps to Austria, some 5 to 15 centimetres of snow could fall. Behind it, high-pressure influence increases rapidly.
After that, a strong westerly to south-westerly flow seems to set up again. Models still differ a lot about the exact outcome, but from Thursday onwards the precipitation chances increase a bit again. GFS seems to give mainly some snow for the northwestern Alps with a western flow. The European model, on the other hand, keeps it mostly dry until the turn of the year. All in all, it is likely that temperatures will remain quite high for the time of year for longer.