Another southern Stau on its way


By Henri on 29 December 2020 · 3

What a winter for the southern Alps…yesterday they got hit again by lots of snow and there is even more to come by the end of the week! On a large scale, many regions received 40 to 50 centimeters of snow. In some regions like Osttirol more than 30 to 40 centimeters of snow fell within just 6 hours, like here in Lienz!

White in the city of Lienz in Osttirol
White in the city of Lienz in Osttirol

Snow in Trento, Italy at 400 meters
Snow in Trento, Italy at 400 meters

Even many low-located valleys in Italy received up to 30 centimeters of snow. Trento in Trentino where the garden of wePowder user Matteo turned into a winter wonderland (and that’s at 400 meters), but also Champoussin on the Swiss side of Les Portes du Soleil got 30 cm. As expected, the föhn hit the Northern Alps pretty hard, with wind gusts up to 140 kilometers per hour in the typical föhn locations.

High pressure above the Atlantic
High pressure above the Atlantic

Low temperatures
Low temperatures

A high pressure system dominating above the Atlantic Ocean causes a blockage of the zonal flow. Low pressure systems are not able to follow their usual eastward track towards Europe. This situation we’re currently experiencing does not particularly result in much snow for the Alps, but at least the Alps are in the upcoming days dominated by fairly low temperatures. We will still have some chances for some snow showers, but they will deliver less snow. So let’s zoom in a bit and see what this means for the different regions in the Alps.

The front on Tuesday
The front on Tuesday

Under influence of the low pressure above Denmark the Western Alps will receive some snow showers today. It’s nothing big. I expect around 10 centimeters in the Northern French Alps and in West-Switzerland. The arctic origin of this air will cause that even the lowest valleys receive some snow.

The rest of the Alps will stay mainly dry today. Only the Dolomites, the southern part of Austria and the regions further to the east will see some light snowfall during the afternoon. Due to the light Südföhn situation the Northern Alps will receive some sunshine, especially in the morning and early afternoon. Tomorrow, the western Alps can still expect some snowfall during the day, but it won’t be much more than a couple of centimeters. The north side of the Alps will stay mainly cloudy during the day, with now and then some snow flurries which won’t lead to significant amounts. The largest changes of sun are for the southern part of the Alps.

The front on Thursday
The front on Thursday

On Thursday the eastern Alps will be dominated by sunshine throughout the day. The western part of the Alps will start the day with some clear skies as well, but a new front will approach from the west with some new precipitation. Again, it won’t be that much, but the Northern French Alps can still get another 5 to 15 centimeters of fresh snow until Friday morning.

Southern Stau coming in
Southern Stau coming in

After a fairly calm end of 2020, the first days of 2021 will be amazing for the southern Alps. Like the other Südstau settings, a low pressure core above the Mediterranean Sea provides the advection of moist air masses towards the southern Alps.

Great colours again!
Great colours again!

The forecasts on wePowder are powdered by our friends at Ortovox

The weather models seem to agree that lots of snow is possible by the end of this week. Also our forecast map is showing some beautiful colours again. The European model shows up to 1 meter of snow for the Julian Alps and the southern Dolomites. Further to the west, in Lombardy and Ticino there is still more than 50 centimeters of fresh snow possible until Monday. Piemonte and the inneralpine regions like Südtirol will receive much less. The American GFS model is still not sure and creates major differences in model output in terms of precipitation. The different runs yesterday forecasted up to 1 meter of snow for the Southern Dolomites, but this morning the model is predicting less deep conditions for Ticino and the Dolomites, with about 30 centimeters of snow.

Both models agree that the temperatures will increase a bit during the snowfall, but will be still low enough to keep the snow line below 1000 meters for most of the time. Only during the coarse of Saturday the snow line can rise temporarily a couple of hundred meters higher.

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Comments


  • rich_a_potter
    Tourist
    rich_a_potter op 31 December 2020 · 14:15
    hey Henri, stupid question but the T on the pressure map above, I'm guessing that's the low pressure areas - what does T stand for....
  • Quelle
    Beginner
    Quelle op 2 January 2021 · 20:28
    Yeah a 'T' is in German (and probably other languages) the symbol for an area of low pressure.
  • Jenson
    Jenson op 4 January 2021 · 15:10
    Yes T is German and stands for Tief (Low) and H stands for Hoch and also High in english. So it means Tiefdruckgebiet and Hochdruckgebiet.
    Which means what @rich_a_potter already suggested. low pressure areas and high pressure areas.

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