We are in the middle of a warm phase in the Alps. In the past few days, the Western and Northern Alps have had to deal with a lot of precipitation and a high snow line. From now on it will be a lot drier, sunnier and a bit warmer due to increasing high pressure. Only after the weekend a change is on the weather charts again and it looks like the Alps are diving back into winter.
In this weather report:
Most areas weathered yesterday's rain well. It is especially the lower northern areas that are having a harder time. Higher up, it snowed 30 to 50 centimetres yesterday in for example Valais. In total, up to one metre of snow fell locally in the high mountains in the north-west over the past few days. Rather surprisingly, the snowline stayed nice and low for a while. As is often the case with a warm front, this was due to the phenomenon of evaporative cooling. The wind was weaker, especially in the narrower and deeper valleys, which allowed the cold to hold even better. At the edge of the Alps, however, the snowline rose quickly. At the top, there was a lot of heavy wet snow, which increased the risk of avalanches.
Today it clears up well in most parts of the Alps. Only in Austria the clouds remain a bit more persistent and there may be some rain in the east until the afternoon. Snow only falls well above 2000 metres because the heat has also arrived here. Elsewhere, the day will be fairly calm with, especially in the Western Alps, more and more sunshine.
Friday, Saturday and Sunday will be sunny and above all very warm thanks to a high pressure area over the Alps. Very warm air will be brought in from the south-west. In the French Southern Alps, the temperature at 1500 metres will be above 15 degrees. On sunny slopes you can find spring conditions with firn everywhere in the Alps. Please note that rain and high temperatures increase the risk of wet snow avalanches. In Austria, Switzerland and France we see avalanche danger 4 in large areas. Please read the avalanche bulletins carefully before setting off.
We see some great developments in the weather models with more and more signs for a return of cold. From the night of Sunday to Monday, a cold front will approach from the west, which could bring some snow, especially on the northern edge of the Alps, but most of the precipitation will pass by to the north of the Alps. Really cold air is not there yet, so the snowline will not be very low. At this moment, it looks like the snowline will start around 1500 meters and could drop a few hundred meters during Monday. Much more than 10 centimetres seems not to be possible at this moment.
From the middle of the week (night from Tuesday to Wednesday as it looks now) there is more to come. The wind will turn to the north and cold air will reach the Alps, causing the snowline to drop to the lowest levels. However, it's still unclear how much precipitation this will bring, because the Azores High is approaching quickly from the west, which might dampen the snowfall. The amounts above show the potential of the weather situation, but don't focus too much on the exact amounts yet.
This was the last weather report of 2021. A new weather report will follow on Monday 3 January. I wish you all a happy New Year! Let's hope for a snowy 2022 in which we can increase the number of PA's!