Calm returns after great April days - Some snow later this week?

For quite a few ski resorts, this was the last weekend of the season, but at least they ended the season with a blast! In large parts of the Northern Alps, we saw fantastic conditions with great amounts of snow. This week will remain changeable in the Alps, but large amounts like we have seen in recent days will not fall again.

Vb-low

Responsible for this snowfall was the Gegenstromlage with a low-pressure core over northern Italy and a north-westerly flow at low altitudes in the Northern Alps. Initially, the continuation was still uncertain, but the low-pressure core followed a Vb path (with a northeasterly course), allowing very large-scale snowfall. With a northeasterly flow, some more snow was pushed against the eastern Swiss Alps and westernmost Austria over the weekend.

Persistently changeable

This week starts a lot calmer. The real stau precipitation has now passed, but with a high-pressure area over Scandinavia, the Alps remain under the influence of a rather fresh continental easterly flow. It means we will see some more cloudy days especially on the northern and eastern sides with precipitation possible especially on the alpine northern edge. In the inner-Alpine areas, however, it may clear up now and then. In the western Alps, the sun has much more room, as shown in the satellite image.

Mid-week more snow?

By mid-week, precipitation chances increase a little further. An upper-level low from an unusual angle could start bringing more snow from Wednesday onwards. On the surface weather maps, this pool of cold air is barely visible, but in higher air layers this bubble of cold air will cause instability and precipitation. Meanwhile, the models calculate a rather unambiguous trajectory of this upper layer: from Poland (Wednesday during the day), the cold air bubble moves westwards towards Benelux/Northern France (Thursday evening).

Wednesday, this upper-level low will bring snow from the north into Austria. Thursday, the upper-level flow turns to west to southwest, with snow likely in the inner-alpine areas, the Swiss and Italian Alps. The snowline here will be around or just above 1,500 metres, in the southern Alps also possibly towards 2,000 metres. In Austria possibly temporarily dropping to around 1,000 metres.

Exact amounts are still difficult to determine due to erratic nature of such an upper-level low. In Austria and Switzerland, some 10 to possibly 20 centimetres could fall, especially in the areas on the northern edge. In the southern Alps, precipitation seems limited for now to regions such as Ticino where ski resorts are no longer open. It is possible that, for example, Tonale - Presena and perhaps the Tyrolean glacier areas could pick up some 10 to maybe 20 centimetres.

Transition to southföhn

After that, it seems to warm up strongly, especially in the Northern Alps, due to increasing southföhn conditions, with temperatures reaching around 20 degrees by the weekend. A possible new colder and changeable phase is not out of the question after that. More and more members in the models’ ensembles seem to opt for this option. An interesting trend, but we will have to wait and see how the models calculate it in the coming days.

Read also:

• What is a Sudden Stratospheric Warming?
• What is an ensemble forecast?
• What are low- and high pressure areas?
• What is a northstau/nordstau?
• What is a southstau/südstau?
• What is föhn?
• What is a retour d’Est?
• What is the jet stream?