Southern California, already reeling from days of flooding, thunderstorms and tidal surges, braced for even more furious weather yesterday, as forecasters warned of the arrival of yet another powerful storm.

A new weather system, forecast to be the most intense of the past week, was expected to spawn more wind, rain and even small tornadoes in the state, which has suffered an unrelenting barrage of inclement weather.

Yesterday’s forecast is “definitely going to be the main event” of an eventful climatological week, Bill Patzert, a specialist at California’s Jet Propulsion Laboratory, said.

Rainfall was expected to total as much as 3.8 centimetres per hour, which could cause flooding not only in low-lying areas, but in the state’s saturated foothills and mountains.

Meanwhile, rising flood waters also were causing problems throughout southern California. Local news programmes broadcast numerous reports of stranded motorists who had to be plucked from their cars after becoming trapped by raging flash floods.

Officials warned residents, particularly those near local creeks and waterways, to take the risk in earnest.

“This is not a playground. This is no time to do extreme sports,” said Jack Wise of the Los Angeles Fire Department.

“Even 15 centimetres of water in the flood control channels is enough to wash you down the river... There’s nobody to hear you scream,” Mr Wise said.

Officials in Los Angeles County order the evacuations of hundreds of homes in the shadow of the denuded San Gabriel Mountains, which recent fires have made bereft of vegetation and where there was a high risk of flooding and landslides.

“If you fail to comply, it could result in death,” Los Angeles County Supervisor Michael Antonovich said.

California Governor Arnold Schwarzenegger meanwhile has declared a state of emergency in a half dozen southern California counties because of the storms. Weather officials said the rain would be accompanied by winds between 24 to 40 kilometres per hour and gusts of up to 100 kilometres per hour.

Heavy snows, rain, winds and lower-than-usual temperatures have buffeted the western US throughout the weekend, hitting Oregon and California especially hard.

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