WeatherBlog 6 2024/25 | Turbulent Christmas weather

General weather situation

The active westerlies and Atlantic storm systems are also reflected in the ECMF's weather regime probability graph. Wetterlagenwahrscheinlichkeitsgraphik is an approximate translation of "weather regime frequency ensemble forecast" Graphik and we use the word here primarily to challenge the automatic DeepL translation for PowderGuide in English with a German composite word!

In any case, we are currently seeing a strong tendency towards the "ATR" - Atlantic Ridge - and NAO+ patterns in the weather situation probability graph and for the next few days. NAO is the North Atlantic Oscillation and the NAO index is positive when the Icelandic Low and the Azores High are both strong. The resulting pressure gradient over the North Atlantic produces the westerly flow and therefore often humid, mild westerly to north-westerly weather in Central Europe. "ATR", on the other hand, refers to high pressure over the Atlantic, which extends relatively far to the north and thus also displaces the Icelandic low that we would need for NAO+.

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500hPa Geopotential und Bodendruck, Nordhemisphäre, GFS Prognose für Donnerstag. Zonale Strömung mit kleinen Wellen über dem Atlantik. Ein Tief streift den Alpenraum von Do. auf Fr. und bringt etwas Schnee.

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Prospects

Translated into Alpine weather, the weather situation probability graphic tells us that the high pressure (ATR) of the last few days will change to more turbulent "westerly weather" (NAO+) from today (Wednesday). Not much will happen today, the rather mild air will stay with us and it will gradually become cloudier. On Thursday, we will feel an approaching area of low pressure (also shown in the graphic above right) in the form of a Föhn wind downstream of the trough, i.e. a southerly flow to the east of the trough axis, and a subsequent change in the weather with precipitation and a falling snow line. The trough axis moves from west to east and everything (Föhn, then precipitation) happens first in the western Alps and then somewhat delayed in the east. On Friday, it will remain widely cloudy, quite windy and fairly cold. Saturday will bring a brief intermittent high and is expected to remain dry with a relatively friendly weather character.

Wetterlagenwahrscheinlichkeitsgraphik: Tägliche Wahrscheinlichkeiten für vier “Wetterregime” und eine graue Zwischenlösung, die sich nicht eindeutig zuordnen lässt. Neben NAO+ und NAO- gibt es Atlantic Ridge (ATR) und “Block” (blockierendes Hoch über Skandinavien).

Snow under the Christmas tree?

Things will get interesting again from Sunday. It currently looks like there will be heavy precipitation, with a low snow line at first and a rising one from Monday/Tuesday. We are hoping for a substantial supply of snow at least for the high and medium altitudes and would like to avoid the traditional Christmas rain event at >2000m this year. Substantial snow currently seem likely, and rain is within the realms of possibility. We take the liberty of exclusively quoting a personal message from the oracle: "There should be an alarm at the weekend. Still questionable for Friday. So-Di quite certain."

For the Christmas holidays, the crystal ball sees warming temps and high pressure pushing in from the west. The questions relevant to skiing are probably how quickly it will get warmer between Sun. and Tue. and how much of the precipitation will arrive at what altitude and in what aggregate state.