Flash flood watch expanded, heaviest rainfall to come as storm charges into SLO County

Update: 6:30 p.m.

Several areas in South County saw flooding on roadways Wednesday as the rain poured down on the low-lying communities.

CHP declared a hard closure of the Highway 1 at 13th Street in Oceano about 8:35 a.m. The road was reopened around 12:15 p.m., but closed again about 6 p.m. Drivers are asked to used alternate routes and exercise caution.

In Avila Beach, workers about 4 p.m. were working to pump water from a flooded First Street. Water there was between one and three inches deep. The one-block portion of the road was closed to vehicles while crews worked. More flooding could be on the way for South County.

See crews try to clear flooded roads in Avila Beach:

Ray Dienzo, technical unit supervisor for San Luis Obispo County Public Works, said the Arroyo Grande Creek would likely reach "full storm" stage overnight. The water level there reached a peak of about 25 feet on Wednesday according to Public Works. Full storm stage, or the level at which county personnel are notified to closely monitor the stream, is 27 feet.

Dienzo said the low-lying area, including a large portion of Oceano, would flood if the water reached 30 feet.

Update: 5:15 p.m.

A woman was killed Wednesday afternoon in a weather-related car crash on Highway 41 west of Atascadero, according to the California Highway Patrol.

The woman — who investigators believe was about 19 years old — was driving south on Highway 41 near Old Morro Road West about 12:45 p.m. when she lost control of her vehicle, which tumbled down an embankment, said Officer Jordan Richards, a CHP spokesman.

For more on this developing story, go here: Woman killed after car tumbles down embankment on Hwy. 41

Update: 3:15 p.m.

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.

For a full weather forecast, go here: Heaviest rainfall still to hit SLO County. Here's what to expect

Update: 2 p.m.

Santa Rosa Creek Road in Cambria has reopened and the rock slide has been cleared, according to SLO County Department of Public Works. The agency announced the reopening about 1:45 p.m.

Separately, Highway 41 was partially closed between San Gabriel Road and Los Altos because of a car crash. According to Atascadero police about 11:40 a.m., crews will need about an hour to remove a vehicle that went over the roadway last night. The roadway is expected to fully reopen by 1 p.m. As of 2 p.m., it was unclear whether the road was fully reopen and there were reports of a second, fatal car crash on Wednesday afternoon.

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Update: 12:30 p.m.

According to local PG&E meteorologist John Lindsey, San Luis Obispo County and the Santa Lucia Mountains could see up to 10 inches of rain Wednesday and Thursday. Up to 8 inches of rain could fall in the burn areas of Santa Barbara and Ventura counties.

Original story:

The storm dousing SLO County was causing slides, crashes and flooding on major roads on Wednesday.

In Arroyo Grande, a vehicle spun out and went over the right-hand side of southbound Highway 101 south of El Campo Boulevard about 7:47 a.m., according to the CHP. A woman inside the vehicle received minor injuries in the crash; additional details were not immediately available.

A separate crash happened on Highway 46 East, west of Whitley Gardens Road in Paso Robles just before 8 a.m. In Atascadero, CHP officers responded at about 9:50 a.m. to a three-car crash on northbound Highway 101 south of Highway 41. No one was injured, the CHP said.

Just before 10:40 a.m., a vehicle spun out and hit the center divider on northbound Highway 101 just north of the Highway 58 off ramp in Santa Margarita, according to the CHP.

At 12:25 p.m., the CHP was responding to a single-vehicle crash on northbound Highway 101 a mile north of Highway 58. No injuries were reported.

As well, at 11 a.m., the CHP reported that it had received several calls of a rock and mudslide across westbound lanes of Highway 46, just west of the summit. As of 11:45 a.m., the roadway remained open.

Just before 1 p.m., CHP officers responded to northbound Highway 101 near Laetitia Vineyard & Winery for a yellow Ford Mustang in the bushes on the right-hand side of the road, according to the CHP's incident information page. The car was about 10 to 15 feet off of the road, the CHP said.

At about 1:15 p.m., a vehicle was reported over the side of the road on Highway 41 West at Old Morro Road, according to emergency scanner traffic. The CHP's incident information page reported a solo vehicle collision in that area at about 1 p.m.

Flash flood watch

A flash flood watch will remain in effect until 5 p.m. Thursday, according to the NWS. The watch, which was originally in effect for the burn areas of San Luis Obispo, Santa Barbara and Ventura Counties, was expanded at 2 p.m. Wednesday to include the entirety of SLO County.

"Flash flooding and mud and debris flows are likely in and around recent burn areas in the watch area," the NWS said.

The agency added that rainfall rates, especially in the northwestern portion of SLO County, could potentially exceed 1 inch per hour.

"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.

Highway 1 closures

Highway 1 at Ragged Point is closed between Ragged Point and Gorda in Monterey County due to a rockslide, according to Caltrans. The road closed in SLO County at about 7:40 a.m., according to the California Highway Patrol.

Caltrans said in a news release they hope to have the road reopened by Friday.

This is the second slide caused by the storm: On Tuesday night, a large rock slide forced the closure of Santa Rosa Creek Road near Cambria.

At 8:35 a.m., authorities closed Highway 1 at 13th Street in Oceano due to flooding. The road reopened at about noon, according to the CHP.

Flooding was also reported about 8 a.m. on southbound Highway 101 just north of Laetitia Vineyard & Winery, according to the CHP. Water had made it about halfway into the No. 1 lane of the road and authorities had called Caltrans to come check the drains.

Flooding also caused Highway 1 at Division Street near Guadalupe to close at about 9:40 a.m., the CHP said. As of 11:30 a.m., it was passable, according to the CHP.

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Forecast: Thunderstorms possible

According to PG&E meteorologist John Lindsey, increasing instability in the atmosphere is causing thunderstorms to develop along the coastline.

According to the National Weather Service, there is slight chance of thunderstorms from Wednesday morning until Thursday afternoon. Any thunderstorms will likely produce rainfall rates that exceed 1 inch per hour.

At 8:12 a.m., the NWS issued a flood advisory for south-central SLO County that was in effect until 11 a.m. The advisory also affected northwestern Ventura County and Santa Barbara County.

"Rain rates have already reached 0.25 inches in less than 10 minutes in southwest San Luis Obispo County this morning," the NWS said. The agency added that Santa Barbara County and western Ventura County should expect a sharp increase in rain over the next few hours.

Santa Barbara County

Steady rainfall across Santa Barbara County caused minor roadway flooding and fallen trees Wednesday, according to Southern areas of Santa Barbara County reached the half-inch per hour rainfall rate, which is the minimum threshold for causing debris flows, Noozhawk said. Emergency responders are keeping a close eye on Montecito and Carpinteria for mud flows.

The storm is expected to continue dumping rain on Santa Barbara County through Thursday.

Mandatory evacuation orders for communities below recent wildfire burn areas remained in effect Wednesday. The orders affect about 30,000 people, Noozhawk said.

This story will be updated through the day Wednesday. contributed to this report.