California Hit by Heavy Rains and Flooding as Atmospheric River Hits State
California is currently in the grip of an atmospheric river, which has brought heavy rains and flooding to the state. The rainfall totals are reaching double digits in the mountains north of Santa Barbara, and the situation could worsen with another day of sporadic downpours and isolated thunderstorms. Flood watches are in effect along the entire coastline from Eureka to the Mexican border and across most of the Central Valley, affecting over 35 million people. The threat of additional flooding is expected to last until Wednesday.
The impact of the atmospheric river has already led to debris flows and mudslides, including in Los Angeles. Numerous roads in Central and Southern California have been closed due to high water, mud, and debris. The westbound lanes of the Pacific Coast Highway were blocked by a mudslide in Santa Monica, while large boulders blocked both lanes at the intersection of Malibu Canyon Road and Piuma Road in Agoura Hills. Flooding also caused the closure of a lane on Interstate 5 in Burbank for a period of time.
The hardest-hit areas are between Los Angeles and San Luis Obispo. Montecito has reported 8.84 inches of rain, with even higher amounts in the mountains near Toro Canyon Creek. Most of the Ventura County mountains have received at least 6 inches of rain, with significant rainfall also recorded in Malibu and at Pepperdine University. Downtown Los Angeles has seen less rainfall, but more is expected. If two more inches of rain fall, it would make this February the wettest on record.
Southern California is also at risk of isolated tornadoes or waterspouts, following tornado warnings in the Sacramento Valley on Monday. One of these storms even produced snow in the mountains. Strong winds in central and northern parts of the state have caused trees and power lines to topple, leaving over 10,000 customers without power.
The atmospheric river is expected to weaken by Wednesday evening, but active weather is predicted to return during the upcoming weekend.
Where is the atmospheric river now?
The atmospheric river, which is a stream of deep, tropical moisture originating near Hawaii, is currently being pushed ashore by low pressure off the coast of Oregon. It has made its way down the coast and is now targeting Southern California, particularly San Diego and Los Angeles. The moisture plume will remain over these areas for most of Tuesday. Behind it, a pocket of cold air aloft is moving overhead in connection with the core of the upper-level low pressure, resulting in scattered downpours and potential thunderstorms across California until Wednesday evening. Some of these thunderstorms may produce small hail, funnel clouds, or even tornadoes.
What’s next?
Rainfall:
There is a Level 3 out of 4 risk of flash flooding and excessive rainfall in the Los Angeles metro area. Showers and storms will move rapidly, but there will be constant rainfall over specific areas, similar to train cars moving on tracks. The mountains north of Los Angeles could see an additional 2 to 4 inches of rain, while downtown areas could receive around an inch, or possibly more if downpours persist.
The concern with this storm is not necessarily the total amount of rainfall, which will be less than the previous storm, but rather the high rainfall rates exceeding half an inch per hour. This intense rainfall can overwhelm already saturated ground and lead to further flooding. Central and Northern California will experience isolated showers over the next 36 hours, but the majority of rain has already passed.
Heavy snows and high winds:
Snow levels in the Sierra Nevada will drop from 7,000 to 6,000 feet, resulting in greater snow accumulations at higher altitudes. The resort areas above 6,000 feet may see a few more inches of snow, while the higher peaks could receive 2 to 4 feet of additional snowfall. The Sierra Ridge may experience gusty winds over 40 mph, but the strong winds have mostly subsided elsewhere. In the mountains of Southern California, 10 to 20 inches of new snowfall is expected with snow levels dropping from 7,500 to 6,000 feet.
Looking ahead:
By Thursday, the upper-air disturbance causing the atmospheric river will have moved away, bringing a period of calm weather. However, another atmospheric river is predicted to arrive late Sunday, bringing the potential for more rain and flooding to California.
In conclusion, California is currently facing heavy rains and flooding due to an atmospheric river. The state is experiencing double-digit rainfall totals in some areas, and flood watches are in effect for millions of people along the coastline and in the Central Valley. The threat of additional flooding will persist until Wednesday. The impact of the storm includes debris flows, mudslides, road closures, and power outages. Southern California is also at risk of isolated tornadoes or waterspouts. The atmospheric river is expected to weaken by Wednesday evening, but more active weather is on the horizon for the weekend.
