Once again, it is the turn of the north-west Alps for quite a bit of snow with a focus more towards the west. The run-up to the snowfall has been quite mild and turbulent, read here what I wrote on Wednesday, but from Saturday onwards the snowline will also start to drop a bit. So we start April with PA#12!
In this weather report:
Yesterday, the first cold front already brought several centimetres higher up. The snowline was still very high in the process. With rain on a weak old snow layer, many wet snow avalanches came down again below 2200 metres, as the SLF reported yesterday. Higher up, wind slabs are a problem. With the stormy winds it will stay tricky, also during the weekend!
With a strong westerly flow due to a low-pressure core moving from England to the Netherlands, quite a lot of precipitation could already fall today. In the process, it is still quite mild, so snow will initially fall only in the high mountains. During the day, the snowline will drop from around 1800 - 2000 metres to 1400 - 1500 metres in the evening. In the strong showers reaching the north-west Alps, there will also be graupel and thunderstorms embedded. From time to time it can really dump. With this strong westerly, the wind is also very present, so wind slabs remains a serious problem especially at higher altitudes.
Most snow will fall in the French Northern Alps (Haute-Savoie and Savoie) and Wallis (especially the western part). Around 20 to 30 centimetres of snow could fall here, with up to half a metre locally possible in the high mountains (>2500m). Further east, the amounts decrease significantly. Up to and including the Arlberg, it will stay at about 5 to 10 centimetres, locally with a heavy shower also possibly some more.
In the second half of the upcoming night, it will cool down further from the northwest, bringing the snowline to around 1,200 metres, but possibly rising slightly to 1,400 metres during the day. Again, it is mainly the same regions that can expect a lot of snow. Here again, some 10 to 30 centimetres may fall, locally some more. For the regions east of Wallis, the amounts have been slightly reduced over the past runs. Up to and including the Arlberg, I expect around 10 to 20 centimetres of fresh snow until the end of the day. Behind the Arlberg in Tirol, the amounts are of course a bit lower, although some 5 to 10 centimetres could also fall in Salzburgerland.
After a in many places dry night into Sunday, another precipitation area will follow from the north in the morning. The northern stau areas could receive around 10 to possibly 20 centimetres, although here too there is still some uncertainty in the models about the exact amounts! Most French areas won't need to count on very large amounts anymore.
Clearings are only possible on a large scale in the Western Alps and Switzerland from Monday onwards. On Monday, the intensity of the snowfall in the Northern Alps already decreases significantly, especially in Austria, where a northerly flow could keep it cloudy and lightly snowing a bit longer. Here it will also remain quite cold through Wednesday. In the Western Alps, temperatures rise a bit earlier, but it won't get really warm here either until mid-week.
The really big amounts are going to fall in a more limited area around the Mont Blanc massif this time. In the higher regions, 50 to maybe 80 centimetres are possible here. Of course, the rest of the north-western Alps will also pick up, but less. I think our model is a bit too generous with the amounts at the moment, but it does give a good indication. Above, I added another map of precipitation amounts until Sunday morning according to Kachelmann's Mitteleuropa Super HD model. These amounts are also a bit on the high side in my opinion, but the largest amounts are clearly for the French Northern Alps and western Switzerland. The full amounts are only for the high alpine regions because the snowline is still fairly high today, but there will also be quite a bit of snow above 1500 metres. Haute-Savoie and (the west of) Valais are good options.
Further east, therefore, it remains to be seen whether so much snow can start falling here as well. Despite the region normally getting ample amounts with a westerly to northwesterly flow, it is not yet a done deal especially around the Arlberg, but partly due to last week's snowfall as a base, I expect it to be fine here too. So here you will probably have to settle for some less fresh snow, but at the same time we know that a surprise in the Arlberg is never out of the question.
The wind is still very strong today resulting in many closed lifts. Fortunately, the westerly flow is already weakening a bit tomorrow and Sunday will be even calmer. With the large amounts of fresh snow, the tricky situation with wind slabs should not be underestimated! Also for the weekend, it is of course important to keep a close eye on local avalanche reports.