Heavy rains have been flooding the northern California coast for the past few days. Some areas received up to 500mm of rain. Roads have completely disappeared under water, landslides are endangering several buildings. It’s the heaviest rain streak in Sana Francisco since 1871.
Enough snow to cover a house
And meanwhile, less than 300 km east of the coast, the Sierra Nevada mountains could receive up to 7.5 meters of snow. That’s the height of a three-story building that the falling snow could reach in the next two weeks.
Unity is strength
It is the combination of a weather bomb, a drop in atmospheric pressure of at least 24 hectopascals in less than 24 hours, and an atmospheric river that will create this extreme phenomenon. A weather bomb mainly generates strong winds, as well as heavy rains and/or heavy snowfalls. Atmospheric rivers are large successions of clouds that form in the tropics and reach higher latitudes. They form about a kilometer above sea level. Quite narrow, they can therefore stretch over thousands of kilometres, thus dumping precipitation for several days. The combination of these two phenomena multiplies their impacts. This region will therefore be a paradise for skiers … if they can get there.