The National Weather Service expanded its flash flood watch to include all of San Luis Obispo County on Wednesday afternoon, with the heaviest rain still on the way.
"Flash flooding and mud and debris flows are likely in and around recent burn areas in the watch area," the NWS said. In San Luis Obispo County, "the heaviest rainfall intensities are expected later tonight into Thursday morning."
The agency added that rainfall rates, especially in the northwestern portion of SLO County, could potentially exceed 1 inch per hour.
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"Highway 1 north of Morro Bay especially at risk for flooding with rock/mudslides," the NWS tweeted.
The peak of the storm is predicted to arrive at 4 a.m. Thursday, when rainfall rates are expected to reach 1 inch per hour, according to PG&E meteorologist John Lindsey.
By noon Wednesday, most San Luis Obispo County locations recorded between 1 and 2 inches of rain, Lindsey said. Rocky Butte recorded the most rain, at 3 inches.
By Wednesday afternoon, the storm had already caused multiple car crashes and road closures throughout SLO County.
"We're already seeing significant rain everywhere," Lindsey said.
Moderate to heavy rain will continue into Wednesday night, Lindsey said, with the heaviest rain arriving Wednesday night through Thursday morning.
By 4 p.m. Thursday, the rain is expected to taper off. A break in the rain is expected Friday and showers are forecast for Saturday and Sunday, according to Lindsey.