California residents near Big Sur have been told to stock up on enough supplies to last them at least two weeks ahead of a new storm.

Intense flooding and snow is expected in the state, which is still recovering from extreme weather that left mountain communities under several feet of snow.

Experts say the combination of rain and snowmelt could lead to extreme flooding.

California has already had one of its wettest winters on record.

The state has been hit with back-to-back storms in recent weeks.

Nine atmospheric rivers - which occur when water evaporates into the air and is carried along by the wind, forming long currents that the sky that can bring severe rains and mountain snow - came through the state in early January.

Up to 7ft (2.1m) of snowfall earlier this month left residents in the San Bernardino Mountains stranded.

The San Bernardino County Sheriff said the department has rescued 100 people in the region so far, but at least one person has died.

Volunteer helicopters are bringing in supplies for those still trapped in the mountains without enough food and water.

Northern and central California are expected to bear the brunt of this storm though, with 16 million people under flood watches as of Wednesday.

Noah Diffenbaugh, earth system science professor at Stanford University, says the context of this storm is important - while the current forecast might not look too severe, the extreme weather that preceded it makes it more risky.

"We have had a lot of moisture accumulation, saturating soils and so the potential for landslides, debris flows, is enhanced," he told the BBC.

Incoming rain could rapidly melt existing snow putting lower elevation areas at high risk of flooding.

Coastal areas could see as much as 5in (12.7cm) of rain.

Big Sur, south of San Francisco, as well as the central coast and Bay Area, are under a flood watch till Sunday.

Monterey County is offering residents sandbags to protect their property ahead of the storm. Earlier this year storms caused landslides near Big Sur, closing off a major highway and cutting residents off from supplies.

Fearing a repeat, Big Sur residents have been urged to gather essentials now..

Meanwhile, in high elevation areas residents have been told to try to clear their roofs of snow as rainfall could weigh down existing snow leading to potential roof cave-ins.

Central parts of the state with elevation over 8,000ft (2,438m) - including Yosemite National Park - could expect to get 6ft (1.8m) of snow.

Yosemite National Park, closed from the last winter storm, said it will remain closed till 12 March - possibly longer.

In terms of how this storm affects California's drought, Dr Diffenbaugh says the overall "outlook is certainly a lot better now than it was in October" but there remain "accumulated water deficits".

About 30% of the state's water supply is dependent on snowpack, which is accumulated snow on the ground, according to the California Department of Water Resources.

"The larger amount of snow accumulation is great news from a water resources point of view" but it "does create some elevated risk of spring flooding", Dr Diffenbaugh said.

Source:
courtesy of BBC NEWS

by Chloe Kim | BBC News, New York

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