It's been snowing in the Alps the last 24 hours, but there's much more to come the next 48 hours. A low-pressure area above the Adriatic Sea sends two throughs of upper level lows (zones of cold air at very high altitude) towards the Austrian Alps in the night of Monday to Tuesday. These zones of cold air will enter the east of Austria slowly but surely. As a result the low-pressure area will move really slow as well and this will result in lots of rain and snowfall.
You can expect a lot of rain in the valleys and snow above 1300-1700 meter in the east of Tyrol, the Salzburgerland, Styria and Carinthia on Tuesday. The snow line might even drop a bit more locally during persistent snowfall. Expect 50-100 mm of rain and locally even more. You can expect between 40-120 cm of fresh snow above the 1700-2000 meters between Monday evening and Thursday morning. The quantities will be huge especially in those areas where the front keeps hanging around. Check our snow maps for all the details.
The more west you go, the less snow will come down. It will definitely snow (thanks to the instability of the upper air) in the French northern Alps, Wallis, the Swiss northern alpine ridge, Graubünden, Vorarlberg and Tyrol, but with 5-20 cm of snow it won't be that much. The proximity of a high-pressure area that moves toward the east on Tuesday will keep the huge amounts of snow at a distance.
Wednesday will start with heavy snowfall and rain in the east of Austria, but the intensity will decrease because the low-pressure area is moving to the east. A current from the north will bring some extra centimeters of fresh snow to the northern Stau regions of the Salzburgerland and Styria. I expect the sun (and higher temperatures) to return there on Friday.
The models are calculating more instability for the long term, which might result in a realistic chance that the Alps can expect some more fresh snow in the last week of September. After a very warm summer, September is the first month in which the weather is cooler than usual. If it was November, we could have been riding in deep powder. Let's hope that this unstable weather will repeat itself later this year!