Tourism authorities in the Jura & Three-Lakes region posted the video online on Monday and it has now been seen thousands of times.
Fog-wave over the Jura Mountains ?❄️? Impressive weather phenomenon captured yesterday by the 1st cross-country skiers of the season. Some trails are now open ?⛄️❄
Snow report: https://t.co/86p1bxC11B / https://t.co/qscJLCTnRU
Webcams: https://t.co/x1xpBSjC8p #Jura3Lacs pic.twitter.com/n3ar0H1h9B
— Jura & Trois-Lacs (@Jura3Lacs) December 16, 2018
Fog waves are something of a meteorological speciality in the Jura range of Switzerland with the Belchenflue mountain on the borders of the cantons of Basel-Landschaft and Soluthurn offering ideal conditions, according to Swiss daily NZZ.
A combination of geographic and weather conditions is required for fog avalanches to form.
A long, flat ridge is required. The windward side of the ridge needs to have a long steep slope – ideally a cliff – fronted by several kilometres of level country.
On the other side of the ridge, which is sheltered from the wind, the slope needs to be less steep so that the fog can slowly drift downwards.
At the same time, to get conditions like those seen in the Jura on the weekend, you need an upper fog line at the same altitude as – or just above – the ridge line.
A high-pressure area is also needed to ensure stable atmospheric conditions. In addition, the wind must also be blowing down on the ridge line as close as possible to vertical so that fog can be pushed along. Otherwise, it dissipates immediately.