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Polar vortex split brings winter in the north – and then the Christmas thaw?

WeatherBlog for freeriders | 03/2010

by Lea Hartl 12/16/2010
Last week finally brought the long-awaited onset of winter in the north. While the base in the south grew with every Italian low, the northern Alps have lagged far behind. All the more pleasing now is the abundant northern accumulation: on Saturday (11.12.), a warm front nestling lovingly against the Alps brought up to half a meter of fresh snow in the (eastern) northern Alps, in addition to the starter that fell the day before.

Last week finally brought the long-awaited onset of winter in the north. While the base in the south grew with every Italian low, the northern Alps have lagged far behind. All the more pleasing now is the abundant northern accumulation: on Saturday (11.12.), a warm front nestling lovingly against the Alps brought up to half a meter of fresh snow in the (eastern) northern Alps, in addition to the starter that fell the day before.

It continued with heavy showers in places and those who caught one of the rare holes in the sun at the beginning of the week were able to enjoy the first serious Northern Alps powder to the full. If, on the other hand, you were outside involuntarily last week and stood around a lot, for example (like me) on a training course, then you have a few uncomfortable days behind you. While it was great to powder in the shelter of the forest, the wind turned many an exposed slope into blown-off slabs of ice, including free face peeling from the swirling artificial snow. Yes, I speak from experience and yes, I was duly annoyed by many a "fat powder here, is sliding down the slopes fun?" text messages.

Icy cold polar air and lots of fresh snow

A low pressure system over Central and Eastern Europe is responsible for the wintry weather, which has been supplying us with frosty polar air since the end of last week (and will probably continue to do so for the next few days). Our low can stay in the same place for so long because it has a useful helper: A strong high is lolling comfortably in the Atlantic and stretching its fingers far up north to tickle the polar vortex.

Polar regions set the pace for circulation

Large-scale low-pressure areas form over the poles in winter due to the negative radiation balance (i.e. the areas receive less energy irradiation than they lose due to radiation and therefore become colder and colder), which set the pace for atmospheric circulation and ensure that smaller highs and lows always move more or less from west to east.

If an annoying high wedge blows warm air into the face of a polar vortex, it may feel severely disturbed and sometimes even split into two independent vortices, resulting in what is known as a polar vortex split.

Thanks to our Atlantic high, the polar vortex is currently almost at this point. Weather changes from the west are blocked very effectively and interesting details tend to happen on a north-south axis, not along a roughly west-east path as usual.

Powder again for the weekend ... and then the Christmas thaw?

The next potential powder is therefore coming from the northwest again and will provide a little refreshment in the known congested areas just in time for the halfway relaxed weekend.

As usual, the future, not to mention Christmas forecasts, is still relatively uncertain. However, every blocking situation comes to an end at some point and there are currently signs of a gradual change in the flow with corresponding moderation after the weekend...

This article has been automatically translated by DeepL with subsequent editing. If you notice any spelling or grammatical errors or if the translation has lost its meaning, please write an e-mail to the editors.

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