This story was last updated at 9:55 a.m. Thursday.

Rainfall rates from a powerful storm soaking Santa Barbara County were lower than predicted Wednesday, with only relatively minor flooding and related problems reported, but heavy rain and possible thunderstorms were expected to hit the region Thursday. 

As of 9:45 a.m. Thursday, a strong cell had dropped about 3/4-inch of rain in an hour on the Gaviota Coast, and the National Weather Service issued a Flash Flood Warning for the Sherpa and Whittier fire burn areas through 12:30 p.m.

“At 9:25 a.m., Doppler radar indicated heavy rain across the warned area. Flash flooding and mud and debris flows are expected to begin shortly,” the warning said. Potential flooding areas include El Capitan State Beach, Refugio State Beach, Lake Cachuma and Highway 154. 

“Residents living in or immediately downstream should take immediate precautions to protect life and property. Quickly move away from the burn area only if it is safe to do so, otherwise shelter in place and move to a second story or the highest location in your home to stay out of the path of fast-moving water and debris flows. Turn around, don`t drown when encountering flooded roads. Most flood deaths occur in vehicles.”

Following a brief period of intense rain about 4:30 a.m. Thursday, the Santa Barbara County Office of Emergency Management sent out a message warning people to comply with mandatory evacuation orders if they hadn’t already.

The orders were issued for South Coast areas below the recent Thomas, Whittier and Sherpa fire burn areas, including the western Goleta Valley, Montecito and Carpinteria communities. 

“The storm is setting up as predicted. Expect heavy rain and debris flows in and below the Santa Barbara County burn areas. Flooding in lowland areas, creeks and streams is possible countywide. If you have not evacuated from the burn areas, leave now. Use caution when driving as road conditions may be hazardous,” the county’s message said. 

Weather forecasters and emergency officials have been stressing that the multi-day storm — fueled by a very wet “atmospheric river” of sub-tropical moisture coming in from the Pacific Ocean — could still pack a dangerous punch before it moves out of the area.

Responders assigned to the storm, including firefighters and California Army National Guard personnel, get a Thursday morning briefing at the Earl Warren Showgrounds in Santa Barbara.  (Mike Eliason / Santa Barbara County Fire Department photo)

Wednesday afternoon and evening, with light or no rainfall in most areas, was considered a lull before the next big wave of the storm. 

“We are referring to this moment as ‘half time’ for this storm because the area is seeing a slight lull, but we have to be ready for the next much stronger part of this storm,” said Rob Lewin, director of the Santa Barbara County Office of Emergency Management.

All of Santa Barbara and San Luis Obispo counties are under Flash Flood Watches through 5 p.m. Thursday due to the potential of high rainfall rates, reaching 1/2-inch or even 1-inch per hour, perhaps more in thunderstorms. 

“Rainfall rates over San Luis Obispo/Santa Barbara/Ventura counties will range from .50 to 1.00 inches per hour with rates in excess of 1 inch per hour under thunderstorms,” the National Weather Service said in its Thursday morning forecast discussion.

As of early Thursday morning, creeks were reported flowing well within their banks throughout Montecito, Carpinteria and other affected areas on the South Coast.

There were numerous reports of minor street flooding, as well as several vehicle accidents on the rain-slick roadways on Wednesday. 

Highway 192 was reported shut down in both directions due to a tree that fell into power lines.

Periods of moderate to heavy precipitation were expected Thursday morning, according to Joe Sirard, a meteorologist with the National Weather Service in Oxnard.

There is also a slight chance of thunderstorms, Sirard said, which could lead to rainfall rates of 1 inch per hour or more.

“While there will be lulls throughout the duration of the storm, the heaviest rain is expected between 5 a.m. and 11 a.m. tomorrow, Thursday,” county officials said. “The foothills and mountains could see up to 0.5 to 0.75 inches per hour, which meets or exceeds the threshold to trigger debris flows.”

The focus of the atmospheric river was shifting to the north Wednesday afternoon, and all of San Luis Obispo County was added to a Flash Flood Watch already in effect for communities below the Thomas, Whittier and Sherpa fire burn areas in Santa Barbara and Ventura counties.

At 7:17 p.m. Wednesday, the National Weather Service issued a Flood Advisory for most of the North County and all of San Luis Obispo County after Doppler radar detected moderate to heavy rain over much of the area.

“Rainfall rates between 0.20 and 0.33 inches per hour will be likely across portions of the county through this evening, especially from Gaviota northward,” according to the advisory. “Locally higher rates will be possible near thunderstorms.”

The advisory was expected to remain in effect until 10:15 p.m., but was extended until 3:15 a.m. Thursday for San Luis Obispo County and parts of the Santa Maria Valley.

A second Flood Advisory was issued at 6:50 a.m., effective until 10:45 a.m., for Santa Barbara and Ventura counties.

As of 6:30 p.m., several areas had set daily rainfall records, including the Santa Barbara Airport, which recorded 1.67 inches, a number that was expected to rise since rainfall was still falling Wednesday night.

Evacuation orders remained in effect for some 21,000 people living in communities below the burn areas in Santa Barbara County, and were expected to remain in effect until Friday morning.

“It looks like rain will taper late in the day (Thursday),” Sirard said, and give way to scattered showers through the nighttime hours.

Cool, dry weather is expected Friday through next Wednesday, Sirard said, although there is a small chance of showers Saturday afternoon and evening.

Mandatory evacuation orders were in effect Wednesday for western Goleta Valley, Montecito, Summerland and Carpinteria areas, affecting about 30,000 people. 

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» Click here for Ventura County evacuation orders and emergency information.

Noozhawk Managing Editor Giana Magnoli contributed to this report.

— Noozhawk executive editor Tom Bolton can be reached at tbolton@noozhawk.com. Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.

San Ysidro Creek flows Wednesday morning in Montecito. (Ray Ford / Noozhawk photo)