Flash Flood Watch issued for Los Angeles ahead of strong atmospheric river, California
A Flash Flood Watch has been issued for Los Angeles through Thursday, February 13, 2025, ahead of the atmospheric river forecast to bring heavy rainfall to the region.
Precipitation forecast map for California until Thursday night, February 13, 2025. Image credit: NWS/WPC
The National Weather Service (NWS) has issued a Flash Flood Watch for much of Los Angeles through Thursday, February 13, as an atmospheric river approaches California.
The watch will be in effect from 13:00 local time (LT) on Thursday to 04:00 LT on Friday, February 14, covering all recent burn scars due to the risk of debris flows and flash flooding.
According to the NWS, there is a high risk of urban flooding on some roads and parking lots, as well as a high risk of swift-water rescues. There is also a moderate risk of small stream flooding.
Residents are advised to avoid roads, adjust travel plans, and stay out of streams, creeks, and rivers.
The heaviest precipitation and greatest impacts from this atmospheric river are expected in 24 hours from Thursday, February 13, into Friday, February 14, according to the Center for Western Weather and Water Extremes (CW3E). Precipitation totals of 75 – 150 mm (3 – 6 inches) are forecast for the Sierra Nevada, Central California Coast Ranges, and Transverse Ranges.
The NWS Weather Prediction Center (WPC) has issued a slight risk excessive rainfall outlook (ERO) for much of coastal California, the Central and Southern Sierra Nevada, and portions of the Central Valley.
Between 125 and 250 mm (5 to 10 inches) of rain is expected in the Sierra Nevada, Central California Coast Ranges, and Southern California Transverse Ranges. Lower elevation areas of Southern California are forecast to receive around 50 to 100 mm (2 to 4 inches) of precipitation.
More than 1.2 m (4 feet) of snow is expected in the Central and Southern Sierra Nevada, with major to extreme winter storm impacts likely in these areas.
According to the California-Nevada Forecast Center, 15 stream gages are forecast to rise above the action stage, while 5 gages are expected to exceed the minor flood stage between Tuesday and Saturday, February 15.
Streamflow remains elevated across much of the Sacramento Valley due to heavy rainfall from recent atmospheric rivers. Additional rainfall this week is expected to worsen flooding in the region.
Heavy snow combined with strong winds is expected to create hazardous conditions over the Sierra Nevada, particularly from Thursday into Friday.
The WPC’s Winter Storm Severity Index (WWSI) indicates an over 80% probability of major winter storm impacts in the Central and Southern Sierra Nevada, while higher terrain areas have a more than 50% chance of extreme winter storm impacts.
References:
1 Short Range Public Discussion – NOAA/WPC – February 11, 2025
2 CW3E AR Update: 10 February 2025 Outlook – CW3E – February 10, 2025
3 Strong atmospheric river to impact California with heavy rain and mountain snow – The Watchers – February 11, 2025
Rishav Kothari is Editor-in-Chief of The Watchers, where he runs the newsroom and covers earthquakes, volcanoes, severe weather and space weather.
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