Southern California is bracing for what could possibly be the strongest storm system to hit the area in years, according to the National Weather Service. Mandatory evacuations have been issued in at least one community ahead the storm.
Rain will arrive along the Central Coast and then move south into Los Angeles and Ventura Counties Thursday evening, according to NWS. It will then intensify Friday midday, with rainfall up to about 1 inch per hour. On Saturday morning, the area will start to see the rain taper off, with scattered showers possible throughout the evening.
The region could get 2-6 inches of rain in the coastal and valley areas but between 5 and 10 inches in the mountains and foothills, with winds adding to the intensity of the storm and its rainfall.
"We're going to get oodles of water," meteorologist Kathy Hoxsie told KPCC. The intensity and direction of forecasted winds are largely what makes this storm so wet.
During a typical winter storm, winds shift from south to north, halting precipitation. In this storm, however, winds coming from the southwest will intensify.
That means two things. Winds will be drawing moisture from the coast and lining up "almost perfectly" to come up against the mountains and drop water.
"The closer [the wind] can get to perpendicular, the more efficient we are at pulling moisture out of the clouds," she said. "That's why our mountains and foothills are going to get dumped on."
The region has not had a storm of this type since 2011 and it has not seen this much rainfall in a single day since 2004.
Officials are concerned about areas recently burned by wildfires.
The City of Duarte has issued a mandatory evacuation order, known as a red alert, for the community within the Fish Fire Impact Area. Effective 7:00 a.m. on Friday, 180 households are to leave their homes, officials said. The city will open the Duarte Community Center for evacuees.
“When you get that much rain in a recent fire area [and] combine that with wind, mud and debris flows are almost certain,” said Karen Herrera, Duarte's deputy city manager.
Glendora issued a yellow alert Thursday. A yellow alert means residents should clear streets of parked cars, trash cans and other objects in case of flooding.
To prepare for the storm, L.A. County workers have been clearing debris basins, especially in the foothill communities, which are likely to receive the most rain.
"It’s critical, when you’re expecting a mud flow of this magnitude, that they be as empty and cleared out as possible to enhance public safety to the maximum," said Herrera.
Crews have been working "around the clock," said Steven Frasher with L.A. County Public Works. "A lot of material came down in the mid-January storms, but the debris basins areas are ready for the next storm."
He said crews from the county's flood maintenance and road maintenance departments will also be on hand when it starts to pour.
Public works crews are also standing by for another round of possible road closures in the Laurel Canyon area, especially around Laurel Canyon Boulevard. The hillsides there could also be impacted by the coming rain, according to Kate Hutton of the city's Emergency Management Department.
"We did leave some k-rails up there, and what that's gonna do is if there's any additional sliding off of that slope, that'll catch any debris that's flying off hill," she said. "So the k-rail will remain up there and hopefully that will prevent any additional impacts to that roadway."
Officials encourage drivers to report anything they see that could block the roads – whether that's a downed tree or mudslides. You can report anything obstructing traffic by dialing 311.
L.A. County issued a press release with these safety and preparation tips:
If you experience flash flooding, move to higher ground and/or the highest point in the house. Stay out of riverbeds and flood control channels during the storm. Water flow during storm is unpredictable and dangerous. Dial 9-1-1 if you see someone caught in a flood control channel.
In the event of thunderstorms, take shelter in a sturdy building. Avoid isolated sheds, garages or small structures in open areas. Avoid contact with electrical equipment or cords.
Follow evacuation orders issued by law enforcement agencies immediately – hesitating or not leaving may put you and your loved ones in life threatening danger.
Drive with your headlights on during rainy weather, and make sure your windshield wipers are working properly before rain starts.
Freeway flooding may happen – avoid driving in pooled water. Standing water is often deeper than it looks, and can conceal tire-damaging debris or make vehicles inoperable.
“Turn Around Don’t Drown.” Don’t attempt to cross swift moving water; as little as two feet of rushing water can sweep a vehicle away.
At Home and in the Community:
Power outages may happen – keep a working flashlight, and a battery operated radio handy.
Help keep your neighborhood flood safe by parking vehicles and placing trash containers away from catch basins.
Avoid parking on streets that may be vulnerable to mud and debris flows.
Report clogged drains, blocked roads or fallen trees in the unincorporated areas by calling the Los Angeles County Department of Public Works Dispatch at 1-800-675-HELP (4357).
Avoid beach areas. Storm surges may cause beach erosion and damaging high surf conditions with dangerous waves and rip currents to coastal areas.
Visit the Los Angeles County’s Storm Season website at http://www.lacounty.gov/LARain to view tips on how to prepare your home, where to pick-up sandbags, and how to register for Alert LA County so that emergency messages are sent to your mobile telephone or e-mail.
Los Angeles County residents, renters, and business owners, including persons with disabilities and others with access and functional needs, may call 211 LA County for emergency preparedness information, and other referral services. The toll-free 2-1-1 number is available 24 hours a day and seven days a week. 211 LA County services can also be accessed by visiting http://211la.org.
You can be a part of our storm coverage by sharing photos and video of the rain’s effect on your neighborhood. Text RAIN to 63735 to share with us and let us know what problems you might be seeing. You can also tag KPCC in photos on Twitter or Instagram.
This story has been updated.