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Climate and Environment

Brace Yourselves — A 'Pineapple Express' Atmospheric River Is On Its Way

Off the shore of the California coast, massive cloud cover is visible.
A look from satellite at the weather conditions Thursday.
(Courtesy NOAA)
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  • This story is no longer being updated. Get our latest coverage: Flash Flood Warnings North Of LA As 'Entirely Visible' Atmospheric River Hits California

If after that last storm you were hoping you'd finally have more time to fix that hole in your roof before water started pouring through it again, you're out of luck. And in some areas, you have to be cautious.

Southern California is in for yet another drenching as an atmospheric river moves into the region. We'll start to see rain late Thursday, but it should wrap up by early Saturday. Those in Santa Barbara should be ready for flooding.

What to expect from the weather today

The further north you get from L.A., the more intense the storm will be.

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Santa Barbara has a flood watch in place, with 2-4 inches of rainfall anticipated. Northern San Luis Obispo County could see 5-10 inches.

In Ventura and L.A., we'll see 1.5 inches max in most places, though 3 inches is possible along the coast. While they don't have flood watches in place, both Ventura and L.A. are warning of potential debris flows, particularly near drainages and recently burned areas.

The counties south of L.A. should largely see 1 inch of rain or less.

You can call this atmospheric river a 'Pineapple Express'

A "Pineapple Express" is a strong atmospheric river pulling moisture from the tropics, which turns into heavy rainfall and snow.

It all comes down to where the moisture is coming from. Every bit of that late February storm came down from the freezing cold north. The current storm's main energy is coming over from the northern Pacific, but the jet stream that's fueling it is bringing up tropical moisture from below Hawaii.

The two are combining off the west coast of North America and slamming into us, as you can see here:

A satellite image of clouds, pulling moisture from the north and mid Pacific regions into California.
You can seen the storm's main energy coming from the northern Pacific.
(Courtesy National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration)

All that means is that this storm is warmer than the last one, bringing with it a whole different set of hazards.

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How will this affect mountain communities?

When it comes to snow-covered mountain communities, warm rain is a concern because it's one of the best ways to melt snow and create all sorts of flooding issues.

That said, the snowpack is so deep in our mountains that it should absorb the 2 inches or so of rain that could fall over 24 hours. Lower elevation snow that's been sticking around in our foothills will likely melt away.

There are other hazards to look out for besides flooding. The warmer weather is going to increase the risk of avalanches at elevations above 5,000 feet — and, wind gusts up to 40 mph can send things flying.

Goodbye to La Niña

La Niña is now officially over, according to NOAA. The climate pattern — indicated in part by cooling waters in the equatorial Pacific — is often associated with drier conditions in Southern California, though this winter it clearly was not.

Our snowpack is at nearly 200% of normal across the Sierra and L.A.’s gotten drenched with 184% of the rain we’d expect in an average year.

El Niño vs. La Niña
  • The climate patterns known as El Niño and La Niña can have substantial impacts on weather in California. They tend to develop some time around March, with one or the other coming along every three to five years, according to the National Oceanic and Atmospheric Administration.

  • But what's the difference between them? Here are the basics:

  • El Niño

    • Tends to last 9-12 months
    • Occurs when trade winds weaken, and waters in the eastern and central equatorial Pacific warm
    • Can result in wetter weather in Southern California and drier weather further north
  • La Niña

    • Can last 1-3 years
    • Indicated by cooling waters in equatorial Pacific
    • Occurs when strong trade winds build, and waters in the eastern and central equatorial Pacific cool.
    • Can result in drier weather in SoCal and wetter weather further north.

NOAA also explains that we could see El Niño start to shape up in time for our next rainy season, though it’s a bit far out to say for sure. If it does, that could theoretically mean wetter conditions than normal (what it’s often associated with), though the last time it came around in 2018, we didn’t see much standout precipitation.

The bottom line is this: Save as much water as you can, because besides hotter temperatures, we don’t know what kind of weather the next year is going to bring.

Staying safe while 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

Safety tips from Southern California Edison
    • 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.

Tips to keep your heating bills down

  • State law requires residential units to have heating systems that can keep indoor temperatures at a minimum of 70 degrees. That means every dwelling unit and guest room offered for rent or lease should offer heating equipment, usually central air conditioning (A/C) or a wall heater. — Caitlin Hernández

  • Use heat smartly to save money: Cranking things like the A/C and wall heaters can be expensive. If money is tight, be judicious about how and when you use your utilities. For example, only use heaters at night or only set the thermostat to around 70 degrees.

  • Open and close those vents: If you have central A/C, look at where the vents are around your home. Are any open in places where you don’t stay long? Practice opening and closing those so warm air only goes where you need it (most vents should have a small toggle lever). Humidifiers can also help you warm things up — and it’s useful to add moisture into our dry air.

  • Adjust your wall heaters: If you have a wall heater, you can change the output by adjusting the knob (usually at the bottom). Since wall heaters can only warm the areas where they’re placed, it’s essential to close doors to rooms you won’t be in so hot air doesn’t get wasted.

  • Turn on your ceiling fan (really): If you have a ceiling fan, try turning it on. This sounds counterintuitive, but there’s science behind it. The direction a fan turns can push air in different directions, and since hot air floats up, you’ll want to move that around. Your fan should spin clockwise to create an updraft to circulate. Not all fans will have this option, though.

Additional storm resources

What questions do you have about the weather we're experiencing?
A massive winter storm is hitting Southern California. We're here to answer your questions.

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