A calm between two back-to-back winter storms allowed residents in foothill communities to continue with flood protection measures as a more powerful system surged toward drought-stricken Southern California.
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About one inch of rain fell in downtown Los Angeles by early Thursday as the storm system moved along the coast from Northern California. Some parts of the region received more rain overnight than the total since July 1, marking the start of what the National Weather Service called the "largest rain event" in Southern California since March 2011.
Most Southern California communities have seen just over one inch of rain since July 1, but Ventura received 1.47 inches overnight. In Venice Beach, 1.02 inches of rain dropped overnight and about 1.50 inches fell in foothill and mountain communities during a one-two punch of winter storms that might bring more rain through the weekend.
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Some of the heaviest rainfall overnight was reported northwest of Los Angeles in Ventura and Santa Barbara counties.
The break between storms Thursday will include a few hours of clear skies before the more powerful of the two systems arrives Thursday evening and into the overnight hours. That storm might bring up to 2 inches of rain in central and southern valleys, 2 to 4 inches in foothill areas and 6 inches of rain in some mountains.
Isolated thunderstorms are possible as part of a system that could lead to problems during the Friday morning drive.
Gusty south-to-southwest winds will buffet mountain areas, especially "over higher terrain," the National Weather Service advisory said. Snow and wind could affect travel along the Grapevine section of the 5 Freeway north of Los Angeles. The conditions could lead to closures along the major north-south route through central California.
- Read: Preparing for the Storm
A wind advisory will be in effect in Los Angeles County in the San Gabriel Mountains and the Antelope Valley from noon today until 9 p.m. Thursday, the NWS said, forecasting south-to-southwest winds of between 20 and 30 miles per hour and gusts of between 45 and 55 mph this afternoon.
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Several freeway crashes and spinouts were reported early Thursday, including a multiple-big rig crash on the 210 Freeway that closed the freeway as crews removed the wreckage.
Flood Threat in San Gabriel Valley Communities
Voluntary evacuations are in effect for the San Gabriel Valley foothill communities of Azusa and Glendora. The neighborhoods are below an area that burned during the Colby fire in January, forcing residents to stack sandbags around their properties for protection from possible mudslides and debris flows as the rain saturates hillsides.
The city of Glendora issued an Orange Level alert Wednesday for residents in the burn area, meaning voluntary evacuations are in effect. Residents are directed to remove vehicles, trash bins and other obstructions from streets prior to evacuating.
The city could issue a Red Level alert, which includes mandatory evacuations. Officials planned to meet Thursday morning to discuss the weather forecast.
Voluntary evacuation orders were issued Wednesday night in Azusa along Ridge View Drive.
Evacuated residents of Azusa and Glendora residents can go to the Crowther Teen & Family Center located at 241 W. Dawson Ave.
Glendora Mountain Road will be closed Thursday morning through noon Monday.
Crews placed concrete barriers along several streets in Glendora, a community of about 50,000 people. More than 18,000 sandbags -- enough to cover four miles if placed end to end -- were been distributed to residents to protect properties from floods and debris flow.
The National Weather Service also warned of the potential for mud and debris flows from the burn area of the May 2013 Springs Fire. The wildfire scorched nearly 38 square miles of the Santa Monica Mountains as it burned from the edges of suburban homes down to the beach about 50 miles west of downtown Los Angeles.
Other wildfires statewide left scarred landscapes over the past year, including a 400-square-mile area devastated by last summer's forest fire in and adjacent to Yosemite National Park in the Sierra Nevada.
Storms Arrive Amid Dry Spell
As for the drought impact, the effects could be more significant than moisture left by a storm earlier this month. That so-called Pineapple Express storm brought rain and snow to Northern California and increased the Sierra Nevada snowpack, but it still remained at 29 percent of normal.
Sierra snow runoff provides a major source of water for California.
- Running Dry: Drought Resources, Updates
Only very small amounts of precipitation reached Southern California, making this week's weather the first major event of the year. Downtown Los Angeles has recorded only 0.23 inch of rain this month, 3.05 inches below normal to date.
The location has received only 1.23 inches since July 1, a deficit of 9.52 inches.