WeatherBlog 18 2023/24 | Some background for the current PowderAlert

Current situation and outlook

The driving force behind the current weather is a strong Atlantic trough centered slightly west of England. Upstream, the trough is flanked by a Greenland high, downstream by high pressure over Central and Eastern Europe. The Alps are positioned between the Atlantic trough and the high pressure in the east in a strong south-westerly flow, which is producing pronounced pressure differences between the south and the north. The result: clouds and precipitation in the south, foehn in the north. Over the next few days, various smaller storms embedded in the large-scale flow will pass through. The first front will arrive today (Wednesday), the second round is expected on Thursday afternoon, then the Föhn will continue. Details can be found in the current PowderAlert and a possible follow-up alert for the weekend. The big uncertainty factor, especially for the precipitation at the weekend, will - once again - be the snow line.

The further development in the crystal ball is still quite uncertain. After a very warm weekend (the freezing level in the current runs beyond 3000m - see also the corresponding PowderGuide weather maps), temperatures are likely to return to a more normal level with a cold front on Monday or Tuesday. None of this is reliable and there is currently no planning certainty for multi-day tours. For the Easter holidays, it is advisable to develop at least a Plan B and a Plan C in addition to a Plan A...

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500hPa geopotential and ground pressure, Wednesday 27.3., GFS northern hemisphere. Strong Atlantic trough, the Alps lie east of it in a southerly flow.

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Early April weather

Temperatures have been well ahead of the season for some time now (= warmer than the climatological average) and “april weather” in March is not surprising. Nevertheless, the WetterBlog briefly flinched last weekend when there was lightning outside during a snow shower. Last weekend was comparatively wintry, with some snow down to below 1000 metres due to a blast of cold air from the north-west. However, the air in the lower layers of the atmosphere was quite warm when the colder air arrived at altitude, resulting in unstable stratification (warm at the bottom, cold at the top). This is rare in winter, as the ground and the air near the ground cannot heat up due to the low solar radiation. When cold air masses move in at altitude, they usually flow over equally cold or even colder air on the ground and the stratification remains stable (cold at the bottom, cold or even warmer at the top -> inversion). Classically changeable April weather is typical when the air at ground level is already relatively warm due to the seasonally stronger solar radiation, but cold polar air still occasionally flows into the mid-latitudes. Last weekend, other thunderstorm ingredients (moisture, lifting processes) were also sufficiently present, so that the late-winter snowfalls were accompanied by thunder and lightning here and there.

Snowfall line for Saturday, March 30, from the PG weather maps. According to the ICON model, precipitation will fall as snow in the red areas. Much too warm!

Misc: Very wet winter months in Germany, melting glaciers in Austria

The past winter half-year (October-March) was the wettest in Germany since measurements began in 1881. The DWD explains this in more detail here. The very low groundwater levels have largely recovered and the multi-year, pronounced drought period in Germany has ended in most regions. Only parts of Thuringia and Saxony-Anhalt are still far too dry at deeper ground layers.

On the occasion of the newly established "World Glacier Day" (from next year always on 21 March) Geosphere Austria draws our attention to the drastic melting of the glaciers in the Hohe Tauern. The Pasterze and its neighbours are in a similar situation to the rest of the glaciers in Austria and the Alpine region - they are disappearing and rapidly losing surface area and volume. We are keeping our fingers crossed that the current storm will at least provide a good supply of snow at altitude. The more snow cover the glaciers have at the start of summer, the better the ice is protected from summer ablation. And of course, more snow is also desirable for the alpine touring season!