The period of deep winter conditions in the Alps comes to an end. A very strong high pressure area forces storms to Scandinavia, allowing very mild air to flow into the Alps for a few days. But this doesn't happen without a struggle. The cold air in the Alps is not going away just like that and the next 48 hours will be dominated by a warm front that dispels the cold air out of the Alps. This leads to a shifting snow line (first it will be rising, then temporarily decreasing again and will rise significantly during the weekend). In addition, there is a strong wind in the high alpine in Austria. Fortunately, there won't be any precipitation from Saturday and the Alps will have todeal with a few mild and sunny days. You can expect new storms after Christmas, when a very powerful jet-steam is approaching the Alps full throttle. Christmas Day is still mild, but the weather will change on Boxing Day. In this forecast:
The Alps are slowly but surely under the influence of a very powerful high pressure area above the Bay of Biscay. Warm and humid air is pushed towards the north side of the Alpsfrom the west and confuses all the models. Especially the amount of snow, the duration of the precipitation and the freezing level are not clear yet. This is not a perfect front. Warm air is sent to the Alps and it gets even warmer after the snowfall. Most precipitation is calculated on the north side of Switzerland and Austria and I expect about 15-30 cm of fresh snow above 1800 meters between Thursday afternoon and Saturday morning. In addition, there is a strong wind in the high alpine in Austria which will result in transported snow (wind slabs).
This results in three red flags in terms of avalanche danger:
It will get more crowded in the Alps next week and the avalanche danger will increase... Make sure that you have the right knowlegde when you ride out of bounds! Always check the local avalanche forecast and adjust your plans to it, always carry an avalanche beacon, shovel and probe and ride with powder friends. Be sure not to get in situations like in the video below.
It starts to snow on the northern side of the Alps in the course of Thursday afternoon. The mild humid air arrives in the northern Alps in the night to Friday. The snow line rises towards 1,800 meters and the freezing level towards 2,100 meters in the French Alps and western Switzerland. The snow line fluctuates between 1200 and 1600 meters in the east of Switzerland and the west of Austria, while it fluctuates around 900-1200 meters in the east of Austria. There will be a cold front coming in in the course of Friday and the snow line will drop on the northern side of the Alps to around 1000 meters. The high-pressure area will move further into the Alps on Saturday and then it will quickly become milder and drier. Biggest question mark in all this is the humidity on Saturday. If the humidity is still high, it will pull in the snow cover and this will result in humid snow below 1800 meters. I am afraid that this will certainly happen in a number of places. But if this does not happen, treeruns are still possible in the east of Switzerland and the north of Austria on Saturday and Sunday. For the other areas: go search for powder above 2000 meters.
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It is sunny in the south and (south)west of the Alps and that also applies for the rest of the Alps from Saturday afternoon/Sunday. It becomes mild and the wind lies down. It's all caused by the jetstream that is situated north of the Alps (see the picture above). As a result, storms are kept at a distance and the Alps have to deal with warm air.
The freezing level rises towards the 2000 meters or higher, but fortunately the air becomes very dry. Because the nights are clear and cold, the moisture can pull out of the snow cover and you might be able to ride some dry powder on the lower shady parts of the mountain on Sunday/Monday. Great days to ride powder, but keep in mind that the fresh wind-drifted snow can cause some trouble in the high alpine in Austria.
The jetstream will hit the Alps again from Boxing day and the weather will change. The biggest question mark is where exactly the jetstream will be located and what its angle will be. Its positioning will determine the exact path of the storm. In the current calculations, it's coming from the west. That would result in some snow for the southern Alps (warm front) and a southern Föhn for the northern Alps, but with the arrival of the cold front the northern Alps will also get some fresh snow. In such a scenario, the French Alps hit the jackpot with a lot of fresh snow. The exact position of the jet stream is decisive for the snow line. When the current turns slightly turns more to southwest that would result in a lot of snow for the southern Alps, while a current from the north brings snow to the northwest.
But we are talking about a period that's about 120 hours away. A lot of things can change...
Stay stoked Morris