Heavy Rainstorm Will Drench LA Overnight Before Moving South
It's about time to plug that hole in your roof, Los Angeles!
The atmospheric river that's been causing debris flows and shutting down roads, is coming for us next. It's expected to park itself over the area Tuesday night, bringing especially heavy rain — as much as one inch per hour — which could overwhelm small rivers and streams, and lead to urban flooding.
And once again, authorities are pleading with drivers to slow down on these wet roads and to not drive into standing water — seriously, very little water can push your car into danger. We've already had a number of deaths this year due to drivers making this mistake. Please do not do this.
Here is the updated afternoon rainfall forecast map through Wednesday evening. Periods of heavy rain tonight will transition to scattered showers Wednesday. The showers will end from NW to SE through the afternoon and evening, lingering longest in the mountains. #cawx pic.twitter.com/S8lrFhL107— NWS San Diego (@NWSSanDiego) March 14, 2023
Latest radar loop, valid at 936 PM:— NWS Los Angeles (@NWSLosAngeles) March 15, 2023
Light to moderate rain continues to move across #SoCal. Ventura and LA counties most likely to experience an increase in rainfall intensity this evening. #CAwx pic.twitter.com/eAHlGKsbNV
Santa Barbara County got hit by the brunt of the storm on Tuesday, seeing 3 inches of rain in some spots. Schools remained closed and roads near Lompoc and Santa Maria were at least partially shut down due to debris.
Meanwhile, residents living in and around Montecito and Carpinteria were told to evacuate. The good news is that the area, known for suffering deadly damage during storms, hasn't reported any substantial flooding or debris flows yet, and evacuation orders for areas around the Alisal, Cave, and Thomas fire burn scars were cancelled as of 5:30 p.m.
Evacuation Orders for the identified properties and areas associated with the Alisal, Cave and Thomas Fire burn scars in south Santa Barbara County are CANCELLED as of 5:30 PM. Take caution when returning home. Expect slick roads and debris in the area. pic.twitter.com/na9iiXjTV6— Santa Barbara County (@countyofsb) March 15, 2023
As of Tuesday afternoon, Ventura and L.A. counties had evacuation warnings in place.
@CountyofVentura Road closures due to local flooding. Visit https://t.co/w90W5iWyBt for more information.— Ventura County Sheriff (@VENTURASHERIFF) March 14, 2023
Cierres de carreteras debido a inundaciones locales. Visite https://t.co/w90W5iWyBt para obtener más información.#VCSheriff #CountyofVentura #VCOES pic.twitter.com/Ow2qs4bvRZ
As the storm migrates South, flood watches will likely remain in effect for much of SoCal into Wednesday.
A list of maps that should display evacuation warnings and orders when they're issued.
- Santa Barbara County
- Ventura County
- L.A. County
- Orange County
- Riverside County
What to expect
By the time this rainstorm wraps up on Wednesday, coastal and valley areas should've gotten between 2 to 4 inches inches of rain, while our foothills could see up to 8.
On Tuesday, rainfall rates exceed a quarter inch per hour, a general threshold of concern for debris flows.
That raises serious concerns about mudslides, particularly in areas that've seen them before and on hillsides that've recently burned.
Think Montecito or any number of spots along Pacific Coast Highway that are regularly inundated with debris during rains.
There's also elevated concern of mudflows up in the mountain areas that've received substantial snow.
“The real threat looks like the foothills at or below 6,000 feet where you have pure saturated ground, continued snowmelt running down the creeks, and then you have this period of heavy rain,” said Alex Tardy, meteorologist with the National Weather Service.
Those above 8,000 to 9,000 feet will likely see a couple of inches of heavy and wet snow by the end of Wednesday.
Concentrated areas of heavy rainfall combined with snowmelt over the higher terrain, and especially the foothills of the central and southern Sierra Nevada will foster locally significant runoff and flash flooding concerns going through the afternoon and evening hours. https://t.co/e4AGq1MWM0— National Weather Service (@NWS) March 14, 2023
Expect high wind gusts starting Tuesday afternoon peaking late at night into Wednesday morning. Wind gusts are expected to reach 30 miles per hour in the coastal/valley areas and 65 miles per hour in the mountains/deserts, according to the weather service.
Understanding flood warnings
Here's an excerpt from our guide to understanding flood warnings:
- Flood advisories are how the National Weather Serivce begins to raise the alarm. The goal is to give people enough time to take action.
- Flood watches are your indicators to get prepared to move.
- A flood warning is issued when a hazardous weather event is imminent or already happening. When one is issued for your area, you need to get to higher ground immediately.
- A flash flood warning is issued when a flash flood is coming or in progress. Flash floods are sudden and violent floods that can start within minutes.
Read more: Flash Flood Warnings? Watches? Here’s What You Need To Know
About the evacuation warnings in Ventura County
Warning in effect Monday (March 13) at 6 p.m. through Tuesday (March 14) at 10 p.m.
- South Matilija Road, Matilija Springs Area — Camino Cielo
- North Fork Springs Road
- Creek Road/Old Creek Road
- Camp Chaffee Road / Casitas Vista Road Area
- Select residences in the 700 block of Grada/Trueno Avenue due to a damaged storm drain
Warning in effect Monday (March 13) at 6 p.m. through Thursday (March 16) at 10 a.m.
- Piru Canyon Road from Northeast Piru to Lake Piru
Warning in effect Monday (March 13) at 6 p.m. through Wednesday (March 15) at 10 a.m.
- Ventura Beach RV Resort
About atmospheric rivers
Expected to wrap up Wednesday, this atmospheric river is shorter lived than others we've seen recently.
Curious why we focus so heavily on these , storm systems when they pop up?
We make a big deal about them for a few reasons.
One is that, on average, they're responsible for roughly half of our precipitation each year. And just a handful of atmospheric rivers can be the difference between a wet year and another bleak, drought-ridden one.
The second reason is that because they can drop so much water, they're also some of our most destructive storms, causing billions of dollars of flood damage to states across the Western U.S.
About this atmospheric river
This atmospheric river is ranked as a 2-3 on a 5-point intensity scale.
• AR 1 (Weak): Primarily beneficial. For example, a Feb. 2, 2017 AR hit California, lasted 24 hours at the coast, and produced modest rainfall.
• AR 2 (Moderate): Mostly beneficial, but also somewhat hazardous. An atmospheric river on Nov. 19-20, 2016 hit Northern California, lasted 42 hours at the coast, and produced several inches of rain that helped replenish low reservoirs after a drought.
• AR 3 (Strong): Balance of beneficial and hazardous. An atmospheric river on Oct. 14-15, 2016 lasted 36 hours at the coast, produced 5-10 inches of rain that helped refill reservoirs after a drought, but also caused some rivers to rise to just below flood stage.
• AR 4 (Extreme): Mostly hazardous, but also beneficial. For example, an atmospheric river on Jan. 8-9, 2017 that persisted for 36 hours produced up to 14 inches of rain in the Sierra Nevada and caused at least a dozen rivers to reach flood stage.
• AR 5 (Exceptional): Primarily hazardous. For example, a Dec. 29 1996 to Jan. 2, 1997 atmospheric river lasted over 100 hours at the Central California coast. The associated heavy precipitation and runoff caused more than $1 billion in damages.
Driving in the rain
Roadway safety experts advised motorists to:
- Check weather and road conditions all along your planned route
- Slow down
- Keep a wider-than-usual distance between your vehicle and the one in front
- Don't drive through standing water — as little as 12 inches of rushing water can carry away most cars, and two feet can carry away SUVs and trucks.
- Make sure tires are fully inflated
- Check windshield wiper blades and replace if necessary
How to stay safe in high winds
- Watch for traffic signals that may be out. Approach those intersections as four-way stops.
- Make sure you have a battery-operated radio and flashlights. Check the batteries to make sure they are fresh. Use flashlights for lighting during a power outage; do not use candles because they may pose a significant fire hazard.
- If you’re in a vehicle with a fallen power line on it, stay in the vehicle and remain calm until help arrives. It is OK to use your cellphone to call 911. If you must leave the vehicle, remember to exit away from downed power lines and exit by jumping from the vehicle and landing with both feet together. You must not touch the vehicle and the ground at the same time. Then proceed away from the vehicle by shuffling and not picking up your feet until you are several yards away.
- Water and electricity don’t mix. Water is an excellent conductor of electricity. Do not step in or enter any water that a downed power line may be touching.
- Do not use any equipment inside that is designed for outdoor heating or cooking. Such equipment can emit carbon monoxide and other toxic gases.
- If you use a generator, place it outdoors and plug individual appliances directly into it, using a heavy-duty extension cord. Connecting generators directly to household circuits creates “backfeed,” which is dangerous to repair crews.
- Leave the doors of your refrigerator and freezer closed to keep food as fresh as possible. Place blocks of ice inside to help keep food cold. Check food carefully for signs of spoilage.
- Check on your neighbors to make sure everyone is safe.
Additional storm resources
Here's what you need to know when storms hit Southern California:
- Tips To Stay Prepared For The Next LA Storm
- Mudslides Can Be Dangerous And Destructive. This Is How You Can Prepare
- Storms Can Bring Lots Of Water — But Much Of It Winds Up In The Ocean
- Your Guide To Driving Safely In The Rain In LA (And Really Anywhere)
- How LA County Prepares For Massive Rainfall — Like The Storm Hitting Us Now
- Flash Flood Warnings? Watches? Here’s What You Need To Know
- Why Atmospheric Rivers Can Be A Blessing And A Curse
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