Dangerous flash floods in the forecast as California braces for tropical downpours

California is bracing for potentially life-threatening flooding as Tropical Storm Rachel barrels toward Southern California, bringing the possibility for torrential rain, dangerous flash floods and damaging winds across the region.

The National Weather Service issued a stark warning Saturday, cautioning that the storm could trigger widespread flooding, force evacuations and leave roads and bridges washed out.

“Prepare for life-threatening rainfall flooding having possible extensive impacts across San Diego County,” the weather service warned.

“Major rainfall flooding may prompt many evacuations and rescues. Rivers and tributaries may rapidly overflow their banks in multiple places.”

“Flood waters can enter many structures within multiple communities, some structures becoming uninhabitable or washed away,” it added, warning that bridges and roads could also be destroyed by the deluge.

Rain bands were already sweeping into Orange and San Diego counties by late Saturday morning, according to the latest Doppler radar imagery, with forecasters warning that the worst could arrive Sunday.

Rachel could dump 1 to 2 inches of rain across coastal areas, valleys and deserts, while higher-end scenarios call for as much as 2 to 4 inches in the mountains.

“Confidence is high that the heaviest rain will occur over San Diego County mountains and deserts,” the NWS warned.

“Areas of flash and urban flooding are probable, especially where the maximum rainfall rates occur.”

Forecasters have also flagged a 40% chance of excessive rainfall triggering flash floods across mountainous and desert areas of Riverside and San Bernardino counties, including Palm Springs, Joshua Tree National Park and Twentynine Palms, according to the San Francisco Chronicle.

The storm could unleash wind gusts of 39 to 73 mph in some areas, snapping trees, breaking limbs and toppling fences and road signs. Powerful gusts could also make driving dangerous on bridges and elevated roadways while triggering scattered power and communications outages.

The heaviest thunderstorms and rainfall are expected Sunday, with gusts of 20 to 45 mph possible in parts of the desert, according to the National Weather Service.

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Rachel’s unusual behavior has also raised concerns among meteorologists, who say the storm is developing amid an emerging El Niño weather pattern and exceptionally warm ocean temperatures off California.

“It’s notable that this is an unusual event that’s being made possible by both coincidence of this early arriving low-pressure trough off the coast of California and the record warm — and I do mean record warm — ocean temperatures off the coast of California right now,” UC Agriculture and Natural Resources climate scientist Daniel Swain said during a briefing Friday, the Los Angeles Times reported.

Officials are urging residents to prepare for rapidly changing conditions, check emergency supplies and closely monitor weather alerts and local news as Rachel moves through the region.

Residents in flood-prone areas should be ready to evacuate if instructed and avoid driving through flooded roads, where even seemingly shallow water can conceal dangerous currents or washed-out pavement.