A record atmospheric river hit the West Coast hard over the weekend, causing flash floods, debris flows, and even death.
The storm, which started in Northern California at the end of last week, brought up to 9 inches of rain to Southern and Central California over three days, causing deadly flash floods that claimed two lives and left a 5-year-old girl missing after she was swept away in Carmel, where her father died attempting a rescue.
Power outages began to climb into the thousands as widespread gusts of 40-60 mph were reported with higher elevations seeing gusts over 80 mph. Trees and power lines were downed in some areas, including in far northwest California, where multiple downed trees required a closure of the Pacific Coast Highway north of Point Arena.
There were 22 reports of flooding in Northern California Thursday, particularly around the Bay Area and Sacramento metro areas. Rainfall totals of 2 to 5 inches have occurred in the foothills of the northern Sierra, as well as the Santa Cruz and Santa Lucia mountains south of the Bay Area.
Rainfall Records Broken Across Central and Southern California
On Saturday, there were quite a few rainfall records broken across Southern California. A record 3.18 inches fell in Oxnard, breaking the old record of 1.80 inches set in 1934. This was also the 3rd wettest November day on record.
A record 2.90 inches fell at Santa Barbara Airport, breaking the old record of 1.92 inches set in 1952. With 6.01 inches of rainfall over the last three days, this was the wettest three day stretch in the month of November. Daily rainfall records were also broken in Sandberg (2.46 inches), Burbank (1.71 inches), Downtown Los Angeles (1.65 inches), Paso Robles (1.49 inches), Long Beach (1.34).
Saturated soils and wildfire burn scars heighten mudslide risks, with officials warning of more rain on Monday in Los Angeles, Ventura, and Santa Barbara counties. Evacuation orders were lifted Sunday evening, but flood advisories continue amid ongoing showers. The band of soaking rain is expected to move through Southern California during the day on Monday, then into Nevada and Arizona Monday night. Scattered showers and thunderstorms are possible in the rest of California.
What is an Atmospheric River?
When that happens this time of year, it can tap a deep plume of moisture known as an atmospheric river. They’re typically responsible for the lion’s share of California’s precipitation in their wet season, from later in the fall through spring.
According to The Weather Channel, an atmospheric river (AR) is a long, narrow plume of moisture transported by winds from the tropics. Think of it like a river in the sky. They often stretch from the tropics or the subtropics into higher latitudes, often thousands of miles long. These thin ribbons of humid air can be identified and tracked in satellite imagery and computer model forecasts.
While this atmospheric river is of moderate strength, when they move slowly, they can wring out heavy rainfall, especially as the warm, moist air piles into hills and mountainsides, enhancing lift.
Atmospheric rivers are beneficial for the West and provide much-needed lower elevation rainfall and mountain snowfall. However, too much of these conditions too quickly, along with gusty winds, can bring hazardous conditions to communities in the region.
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