California and Pacific north-west brace for an atmospheric river – but what is it?

Powerful storm is predicted to be strongest region has seen this season, causing ‘life-threatening’ conditions

Northern California and the Pacific north-west are bracing for what is expected to be a powerful storm that will bring enough heavy rain and winds to potentially cause power outages and flash flooding.

This week’s weather event is predicted to be the strongest atmospheric river the regions have seen this season. Heavy rainfall is expected to begin Tuesday evening with the worst of the event unfolding throughout the rest of the week, causing “life threatening” conditions, according to the weather prediction center for the National Oceanic and Atmospheric Association (Noaa).