What looks like an avalanche of clouds was seen descending on Swiss Alps in Obergoms on Monday during a meteorological event known as Alpine foehn.

Timelapse video shows the “river of clouds” as it makes its way down the Grimsel Pass.

According to the Federal office of Meteorology and Climatology MeteoSwiss, “foehn occurs wherever strong winds sweep across mountain ranges. One of the major effects of foehn is that it brings warm and, above all, dry downdrafts on the leeward slopes, with winds often reaching gale force.”

The federal office also says it is one of the most distinctive weather phenomena.