PA#14: May-PA for the Eastern Alps

Surprise! After a brief mild phase in the Alps, a powder alert follows this week to end the season well. A “Gegenstromlage” is going to bring lots of snow in the eastern Alps! Even after that, it will remain quite cool and changeable.

Still mild today, precipitation front follows later

Today it is still quite mild at first with light southföhn conditions on the northern side of the Alps, but during the afternoon, a precipitation front of a low pressure system with a core over the North Sea follows from the west. The front initiates a changeable phase where a lot of snow will fall, especially in the eastern Alps.

The front itself will give a considerable amount of precipitation anyway. At first still with a high snowline, but behind the front cooler air is already being transported to the Alps. The really interesting developments are for afterwards, as at the same time a low pressure area with its core over the Gulf of Genoa develops over the Mediterranean Sea tomorrow morning. This puts the eastern Alps into a moist southern flow at higher altitudes. With orographic lifting over the Alps, this flow will give a lot of rain and, higher up, snow.

Low snowline due to Gegenstromlage

Notable is the low expected snowline in the eastern Northern Alps. Although the low pressure area over northern Italy provides the southern flow of moist air masses, on the northern side of the Alps a western to northwestern flow prevails, which creates a “Gegenstromlage” with opposite wind directions. The southerly flow won’t descent after the alpine main crest, but continues to rise, resulting in a lot of precipitation at the northern side of the Alps as well. Due to these colder air masses in the lower air layers, it could snow below 2,000 metres as early as tomorrow and even below 1,500 metres on Thursday. Lots of fresh powder will therefore fall on the glaciers! With the continued snowfall until the night of Thursday to Friday, I expect around 50 centimetres of snow in the still-open Austrian glacier areas with outliers of up to 80 centimetres. The largest precipitation amounts are expected further south in Italy and on the Carinthia border, where more than 100mm of rain could fall until Friday morning.

Persistently changeable

From Friday onwards, the intensity of the precipitation decreases again, but the low-pressure area will continue to circulate over the Alps. There is a little more room for clearings, but in the unstable air, new showers may soon develop again across the Alps. The snowline thus remains between 1,600 and 2,000 metres. On Saturday, for now, there seems to be some room for sunshine again, but it can also quickly close up completely again due to increasing cumulus clouds from which some precipitation may fall again during the afternoon. With the low pressure area right over the Alps, detailed weather forecasts for Friday and the weekend are really still uncertain. So I cannot yet say which areas will see more clearings and possibly sunshine from Friday.

Where to go?

With the moist southern high and a more (north) westerly flow at lower altitudes, the Austrian glacier areas can expect a substantial amount of snow. Meanwhile, most of the ski areas are closed, so for lift-assisted powder in Tyrol, you only have Kaunertal, Stubai and Hintertux as options. In addition, in Austria you still have the Kitzsteinhorn near Kaprun and the Mölltal Glacier still open. Until Friday morning, it could really dump here with a snowline (well) below 2000 metres. Visibility will be poor on Wednesday and Thursday, with some clearing only possible from Friday onwards. How good it will still be on Saturday depends on the extent of clearings Friday during the day (solar radiation, it’s May!) and at night (outgoing radiation).

In the Western Alps there will of course also be snow in the coming days, first with the front passing later today and in the coming days in the form of showers, but the long-lasting snowfall will be for the Eastern Alps only.

Outlook

The Alps seem to be under the spell of low pressure for quite some time after that too. A newly developing low pressure area over Italy could once again bring quite a bit of precipitation to the eastern Alps on Sunday. From the northwest, fairly cold air is still flowing towards the Alps, keeping temperatures (just) below normal for the time of year for a long time.

Once again, this spring shows that the high alpine regions often measure maximum snow levels around this time of year. All in all, it is not only a nice end to a rather precipitation-poor winter season, but this snowfall is of course also extremely positive for the upcoming summer. A thick layer of snow in spring acts as sunscreen for the glaciers.

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?