First snowfall on the way with excessive precipitation amounts

A new season with new powder is coming! Another very warm summer is coming to an end and once again the Alpine glaciers have had a difficult period with large ice losses. Fortunately, the glaciers are getting a much-needed first layer of protection in the upcoming week and we are approaching the (hopefully snowy) winter. Still, it is not all positive news, as precipitation amounts may become too much.

In this weather report:

• Still a high snowline at first
• Slightly lower snowline in the north-western Alps
• Strong cooling with a second cold front
• Then a ‘Vb-low’ with lots of snow

Still high snowline at first

From this Sunday, the first cooling starts already and precipitation follows with a cold front. It will still remain quite mild though, with a high snowline dropping to just below 3,000 metres on Monday. Especially in the southern and eastern Alps, very large amounts of precipitation could occur, causing local flooding and landslides. This is because a low-pressure area is also developing over the Gulf of Genoa, sending moist air to this side of the Alps.

In large parts of the Alps, 20 to 50 millimetres of rain will fall, with locally increasing amounts of rain of 100 to 150 millimetres in the Southeastern Alps. This is something that could be important for the weather setting later this week, as much more is going to fall. In our forecast you can see that the expected snow is still limited and only for the highest peaks.

Slightly lower snowline in the north-western Alps

Monday during the day, a westerly flow will bring more precipitation in the north-western Alps, from the French Northern Alps to the Arlberg, with a snowline that could drop a little further to 2500-2800 metres due to the inflow of slightly cooler air.

Strong cooling with cold front - Then ‘Vb-low’ with lots of snow

Calm returns briefly on Tuesday, but a second cold front follows Wednesday evening with a strong cooling from the northwest. The snowline rapidly drops below 2000 metres, but even behind it, colder air continues to flow towards the Alps.

It also causes the development of a strong Genoa Low on the lee side, which then seems to follow a typical ‘Vb’ path (northeastwards towards Poland). The Vb-low draws in large amounts of humid-hot air, which could cause precipitation amounts to rise sharply. The current extremely warm sea water temperatures of the Mediterranean Sea will also add some extra energy to the system, potentially increasing precipitation amounts.

Together with the north-westerly supply of cold air, the snowline could end up surprisingly low. The exact course of the low pressure system cannot be determined this far in advance, but we take a short look at today’s model runs:

The ECMWF main run showed this Sunday morning an option in which the high-pressure area over the Azores quickly exerts more influence over Western Europe, forcing this depression towards Eastern Europe and quickly halting precipitation from the west. In this setting, the Eastern Alps could still get serious snow amounts. The evening run gives all precipitation for the Alps with worrying precipitation amounts for much of the Eastern Alps. The snowline is around or just below 1500 metres, but in the valleys it could still cause flooding and landslides.

The American weather model also showed a typical Vb-setup this morning with sustained snowfall and very large precipitation amounts in the Austrian Alps with a snowline that could locally drop to 1,000 metres. The 12z run of GFS shows the low moving faster towards Poland, with Friday’s decreasing intensity, but Saturday possibly additional pushing from the north again for the Austrian Northern Alps. Temperatures at 1500 metres are around 0 degrees in this case.

In short: we’ll have to be patient for the exact details, but the higher regions in the Eastern Alps will get a lot of snow. In the valleys, the adverse effects of potentially very large amounts of rain must be taken seriously. In the Western Alps, current calculations suggest that it will remain largely dry after the cold front on Wednesday/Thursday.