Southern California storm tracker: Pineapple Express to bring massive flooding, gusty winds through Christmas
Weather Forecast for Monday, Dec. 23
The latest forecast and air quality conditions for the greater Los Angeles area, including beaches, valleys and desert regions.
LOS ANGELES - Holiday travel plans are under threat as a powerful atmospheric river targets Southern California, bringing a week of relentless rain and damaging winds that could cause severe flooding and debris flows, especially recent burn scar areas.
Multi-day atmospheric river
Big picture view:
Forecasters are warning of a very strong, subtropical weather system—an atmospheric river—that will stall over Southern California for five consecutive days.
This system is carrying "copious" amounts of moisture, leading to a high-impact weather event that will likely last from Tuesday through Saturday evening.
Unlike typical winter storms, this is a warm system, meaning heavy rain rather than snow will be the primary concern for most residents.
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A Flood Watch was issued for Tuesday afternoon through Wednesday evening for much of Los Angeles County, with mud and debris flows possible across foothill and mountain areas, including recent burn scars, according to the National Weather Service.
According to the FOX Weather Center, the Los Angeles metro area is under a Level 3 out of 5 risk of flash flooding from Wednesday through Christmas Day morning, with 5-8 inches of rain possible.
Key impacts and hazards
What we know:
Beyond the rainfall, "very strong winds" will pose a threat Tuesday night and into Wednesday, according to the latest forecast.
Mountain peaks could see gusts up to 80 mph, while lower elevations may experience 40-50 mph winds, the NWS said.
Rainfall Totals: Widespread totals of 4–8 inches for coastal and valley areas, with 8–12+ inches expected in the foothills and mountains.
Damaging Winds: A High Wind Watch is in effect. Peak gusts could reach 80 mph in favored mountain passes and 40–60 mph across Santa Barbara, Ventura, and LA Counties.
Flood & Mudslide Risk: Hourly rain rates may exceed 1 inch per hour on Wednesday. This intensity is high enough to trigger mudslides, debris flows in burn areas, and severe urban flooding from clogged drains.
According to the FOX Forecast Center, rain rates could approach an inch per hour, threatening areas near burn scars from January's wildfire disaster with mudslides.
According to the mayor's office, the Los Angeles Fire Department will have stepped-up staffing in place to respond to swift-water rescues or mud and debris flows. Crews from the Department of Water and Power, Street Services and L.A. Sanitation are also on standby.
Timeline of the storm
Timeline:
While Tuesday will start with light rain, intensity will spike after midnight, the NWS said.
Forecasters expect "upslope" areas and south-facing mountains to see the most significant impact, with rain rates capable of clogging storm drains and causing severe urban flooding. Residents in vulnerable areas are urged to take protective actions immediately.
The worst of the weather is slated for Wednesday, but periods of heavy rain will likely persist through Christmas Day, according to the latest forecast.
Monday: The last "quiet" day with temperatures well above normal.
Tuesday: Winds increase rapidly after 10 a.m. Light showers begin in the afternoon, but rain intensity remains low until midnight.
Wednesday: The Peak of the Storm. Extremely heavy rain and peak wind speeds will occur throughout the day.
Christmas Day (Thursday): A second "burst" of heavy rain and strong wind is now expected, potentially causing holiday travel disruptions.
Friday – Saturday: Rain tapers off to sporadic showers, with dry weather finally returning by Sunday.
What we don't know:
While mountain areas are almost certain to see 1"+ per hour rates, there is still some uncertainty regarding exactly how intense the rain will be in the lower elevations of Ventura and LA Counties.
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While not a "convective" storm by nature, isolated thunderstorms are possible Wednesday, which could locally double the rainfall intensity.
Be prepared, NWS warns
What they're saying:
"Hourly rain rates, especially in the upslope areas, should easily top one inch per hour during the peak of the storm on Wednesday," the NWS said. "The heaviest rain will be in the south-facing mountains, but very heavy rain, possibly close to an inch per hour, is possible at lower elevations as well and anyone in particularly vulnerable areas ... or any recent burn scars should start taking protective actions ASAP.
"There will almost certainly be numerous mudslides, severe flooding either from heavy rain or clogged storm drains, and possibly debris flows near recent burn scars," forecasters continued.
"Los Angeles city personnel are preparing for the storm this holiday week," Mayor Karen Bass said in a statement. "First responders, public works crews, and utility personnel are ready to respond to potential impacts due to the weather. Angelenos planning to travel to spend time with family and loved ones this holiday week should use caution on the roads, plan ahead, and stay informed. Sign up for emergency alerts at NotifyLA.org."
When will the rain end?
What's next:
A cooling trend will arrive ahead of the storm, with Monday's high temperature expected to reach 67 degrees in downtown Los Angeles, then decrease gradually to 59 on Friday, according to the NWS.
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Overnight lows will generally be in the 50s for the beginning of the week, then drop into the 40s in some areas later in the week.
A Tesla motorist drives through the rain near the Eaton Fire burn zone as a powerful atmospheric river storm impacts the region on February 13, 2025 in Pasadena, California. (Photo by Mario Tama/Getty Images)
Safety tips
What you can do:
- Clear Drains and Gutters: Ensure storm drains and home gutters are clear of debris to prevent localized flooding.
- Burn Scar Safety: If you live near a recent wildfire burn area, prepare for potential evacuation. Debris flows can move faster than you can run.
- Secure Outdoor Items: With gusts up to 80 mph possible, secure patio furniture, trash cans, and holiday decorations.
- Travel With Caution: Avoid mountain passes if possible during peak wind periods (Tuesday night–Wednesday) and watch for "Turn Around, Don't Drown" conditions on flooded roads.
The Source: This report is based on information from the National Weather Service and FOX Weather. City News Service contributed.