On 10, 11 and 12 February, two cyclonic systems located north of the British Isles caused the succession of warm and cold fronts over Switzerland, generating precipitation as they passed over the country. The cold fronts brought polar air, inducing rather cold temperatures (snowline at approx. 700m) and, those days, the precipitation fell as snow over a large portion of the country.
On 13 February, an atmospheric river approached western Europe from the west-north-west, bringing large amounts of moisture towards Switzerland. An atmospheric river is a narrow corridor of air located at relatively low altitude (0-2km) that transports large amounts of moisture from lower latitudes to the mid-latitudes. It is visible in the figure below where high moisture values are found, i.e. approximatively where the total column water vapor is larger than 20 kg/m2 (green and yellow colors).