The cold, dry wind known as the Bise, which blows across the Swiss plateau, occurs when the air pressure in eastern Switzerland exceeds that in the west. As the wind reaches Lake Geneva it gains intensity as it is channeled through the narrow gap between the pre Alpine mountains and those of the Jura to the north. According to Meteocentrale, the strength of the Bise can be measured by calculating the air pressure difference between Guettingen and Geneva.

The region running from Yverdon through to Geneva is typically hit the hardest. Wind speed rises with altitude, with higher speeds towards the top of the Jura.

Montreux at the other end of Lake Geneva is normally left unaffected, one reason why palm trees can be found in Montreux but not in Geneva.

According to MeteoNews, the Bise will strike between Monday evening and Wednesday reaching a peak late Tuesday morning. MeteoNews warns of snow drifts on the roads. Winds could reach 70 km/h on the plateau and 85 km/h at the foot of the Jura. Vaud is forecast to be the worst affected canton. The image below shows MeteoNews’ Bise impact forecast for the next few days in Vaud.

Frozen spray off the lake will provide photo opportunities. The image below shows frozen lake spray in Geneva in 2012.

Temperatures are unlikely to rise above -4 to -5 on the plateau and -3 by Lake Geneva. However, the wind will make these temperatures feel like -15 C.

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