WeatherBlog 9 2025/26 | Air mass boundary at the turn of the year

Current situation

Let's refrain from complaining about the snow situation in non-Piedmont. After all, much is a question of attitude. Snow is fascinating and there are some particularly interesting processes to observe at the moment! Thanks to the very dry air and the strong sunlight (it may be December, but the cloudless conditions mean that some snow is still falling on south-facing slopes), the beginnings of penitential snow are slowly forming. Instead of melting in the sun, the snow sublimates when the air is sufficiently dry, so the water molecules change directly into a gaseous state. As a result, rough, jagged formations gradually form and the snow surface becomes increasingly bumpy. We are still a long way from the meter-high penitentes of the dry Andes, but this effect has been observed on a small scale on local southern slopes in recent days, provided there was any snow at all. Incidentally, several 100-metre-high penitentes of nitrogen and methane ice are suspected on the surface of Pluto!

Or, as unnamed people from the WB circle of acquaintances like to say: there is little snow, but at least it's not good.

Anyway, the weather is moving a little and the conditions for penitential snow are getting worse. The stubborn, huge Atlantic high is still in the west (or north - it reaches as far as Greenland) and is preventing any westerly weather that could bring large amounts of moisture. Instead, cold air and low pressure will push towards the Alps from the north-east. The first wave of colder air, including a few clouds and even some snowflakes in the far east, reached us yesterday.

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500hPa geopotential and ground pressure, GFS, 31.12. 2025: Blocking high over the Atlantic and Greenland. Cold air flows south over the Alpine region. The small low pressure system, which is currently still a little to the west of Spain, will be relevant for the medium term.

meteociel.fr

Outlook: Colder, snow in the south-east next week?

In the first few days of the new year, this weather character will remain with us - quite cold overall, fresh wind, cloudy in the east and a few snow showers here and there, the further west the more the high pressure dominates. More interesting, albeit more speculative, is the path of a small high-altitude low that will push south past the Atlantic blockade high and is expected to slip into the Mediterranean region at the weekend. The combination of wintry cold air in the north and a Mediterranean low (warm, humid) in the south offers the potential for plenty of fresh snow. Where and how much will arrive and whether it will arrive at all will be largely determined by the air mass boundary between cold in the north and warm in the south. It is not yet possible to say with much confidence exactly where this will be. The current model opinion tends towards PowderAlert-worthy snowfall in the southeast (AT-IT-SLO border triangle) from the beginning of next week. But as I said, a lot can still change!

The PG new snow forecast is currently quite optimistic for Sun/Mon in the southeast, but the forecasts are still uncertain.

PowderGuide Wetter

Farewell to 2025

Globally, 2025 was in all probability the second or third warmest year in recorded history after 2024 and more or less on a par with 2023. In Austria and in large parts of the rest of the Alpine region, 2025 was "only" a top 10 year in the lowlands and the second warmest after 2024 at high altitudes. To welcome in the new year, we recommend avoiding throwing burning objects into forests and meadows as much as possible. There are increasing reports of forest fires in very dry ski areas away from artificial snow slopes. For example, extensive fire-fighting operations have been underway for days on the Nordkette in Innsbruck, because: "Twelve-year-old caused forest fire. The child had set off several pyrotechnic objects during a hike with his family."

Rule of thumb: if the snow conditions in December are more conducive to hiking than skiing, don't set off any fireworks!

Happy New Year to everyone, hopefully not on penitent snow.