Dozens of evacuation orders were in place Friday as a powerful atmospheric river, known as a “Pineapple express,” surged into an already-sodden California, sparking warnings of widespread flash flooding.
Up to nine inches (23 centimeters) of rain were expected in some parts of the state, with several feet of heavy, wet snow falling over mountains where a huge snowpack has built up over months of near-record storms.
Forecasters said the Pineapple Express – so called because it is bringing warm, subtropical moisture from Hawaii – could cause some of that monster snowpack to melt, overwhelming river systems.
“Rainfall totals of 4-9 inches, atop areas with saturated soil and deep snowpack will cause widespread and severe flooding impacts,” the National Weather Service (NWS) warned.
“Higher elevations in northern California and the Sierras will receive a heavy, wet snow leading to difficult travel.”
US President Joe Biden on Friday approved an emergency declaration for the state, clearing the way for federal assistance to help local agencies.
The move came after a request from California Governor Gavin Newsom, who said he was mobilizing resources to help anyone in need.
“California is deploying every tool we have to protect communities from the relentless and deadly storms battering our state,” Newsom said.
The bulk of evacuation orders affect northern California, with seven rivers expected to burst their banks.
Many of them flooded at the start of the year as a daisy chain of atmospheric rivers dumped massive rain on the state.
More than 20 people died as back-to-back storms washed out communities, bringing down trees and causing landslides – and emergency services now are worried the fresh storms could cause more problems.