An atmospheric river is currently unleashing torrential rain across Northern California and depositing substantial snowfall in the Sierra Nevada mountains, creating significant flooding hazards and increasing the risk of mudslides as it progresses southward through the state on Friday.
The storm has been identified as the first major rainmaker of the season, initially evolving into a powerful bomb cyclone, characterized by its rapid intensification before making landfall along the coast.
After unleashing strong winds and heavy rainfall across the northern part of the state on Wednesday and Thursday, the storm is now advancing toward the central and southern regions.
Ukiah experienced a remarkable rainfall of 3.66 inches on Thursday, surpassing the city’s previous record of 3.16 inches set in 1977. Similarly, Santa Rosa Airport recorded a staggering 4.93 inches of rain on the same day, obliterating the daily record of 0.93 inches established in 2001.
According to National Weather Service meteorologist James White from the Eureka office, Humboldt and Mendocino counties saw unprecedented rainfall, with the highest totals reaching 17.7 inches near Laytonville and around 15 inches near Honeydew in the King Range mountains. Weather forecasts predict an additional one to two inches of rain across the region through the weekend.
In Shasta County near Sacramento, Whiskeytown received 12.21 inches and Sims in the Klamath Mountains recorded 13.37 inches, as reported by NWS forecaster Bill Rasch. The area is likely to experience further rainfall, with foothill locations in interior Northern California expecting between two and five inches.
The storm system is anticipated to begin bringing snowfall after Friday, with higher elevations above 6,000 feet expected to accumulate between one and three inches by Tuesday, according to Rasch, who added, “Today is the last big day of rain.”
In a Friday morning forecast, the Weather Service cautioned that “prolonged rainfall will result in an increased risk of flooding, an increased risk of landslides, and downed trees and power lines across the North Bay.”
In the San Francisco Bay area, the rainfall has predominantly impacted Sonoma, Marin, and Napa counties, as highlighted by National Weather Service meteorologist Dylan Flynn in the Monterey office. Santa Rosa has experienced historic rainfall levels, with three-day totals exceeding 10 inches, a record previously set in October 2021.
Flynn remarked, “Over a 72-hour period, we’ve never seen this much rainfall reported anytime of the year. This is the most rainfall we’ve seen in the last 123 years.”
The storm is expected to move beyond the North Bay, affecting the broader San Francisco Bay area on Friday, where around one to three inches of rain are projected across the region before the system begins to decline on Saturday. Following this, it may continue its journey southward into the Central Coast and potentially reach Southern California.
On Saturday, the forecast predicts Los Angeles and Ventura counties could receive anywhere from a tenth to a third of an inch of rain, while San Luis Obispo and Santa Barbara counties may see up to an inch in certain locations.
A subsequent round of rain is anticipated to commence on Sunday and may be “a little stronger than the first but still likely in the ‘beneficial rain’ category,” according to the National Weather Service’s latest L.A. forecast.
Although forecasters indicate a low likelihood of flooding or significant complications in Southern California, there remains a possibility for slick roads that could disrupt traffic flow.
Concern is growing among residents living near the Portuguese Bend landslide area in Rancho Palos Verdes, as increased rainfall contributes to elevated groundwater levels, exacerbating the already troubling land movement.
However, city officials maintain optimism that extensive “winterization efforts,” which include enhancing drainage systems, repairing cracks, and reinforcing canyon walls, will mitigate the impact of any forthcoming rain. Much of the preliminary work has been completed, although some projects are still ongoing. David Copp, the city’s deputy public works director, expressed this commitment to preparedness, stating the initiative aims “to best prepare ourselves for the wet weather season ahead.”
Moreover, the city has reported that certain parts of the landslide have shown signs of recent stabilization, which has been encouraging, although additional rainfall continues to pose a concern for this fragile area.
How can residents effectively prepare for the expected impacts of the atmospheric river, including flooding and landslides?
**Interview on the Atmospheric River Impacting Northern California**
**Interviewer:** Good afternoon! Today we’re diving into the powerful atmospheric river currently causing significant rainfall and snowfall across Northern California. Joining us is meteorologist James White from the National Weather Service office in Eureka. James, thank you for being here.
**James White:** Thank you for having me. It’s a crucial time to talk about the ongoing weather events.
**Interviewer:** Let’s start with the basics. Can you explain what an atmospheric river is and how it’s impacting Northern California right now?
**James White:** Absolutely. An atmospheric river is essentially a narrow corridor of concentrated moisture in the atmosphere. When these weather systems move over land, they can release extraordinary amounts of rainfall and, in higher elevations, snowfall. Currently, we’re seeing this phenomenon bring torrential rain to Northern California and significant snowfall to the Sierra Nevada mountains. The impact has been severe, with flooding hazards and an increased risk of mudslides as the storm moves southward.
**Interviewer:** That’s quite concerning. We’ve heard reports of record-breaking rainfall in areas like Ukiah and Santa Rosa. Can you provide some specifics on those figures?
**James White:** Sure! Ukiah recorded 3.66 inches of rain on Thursday alone, which broke its previous record of 3.16 inches. Santa Rosa Airport took it a step further with 4.93 inches, shattering the old daily record of 0.93 inches. In some mountainous regions, rainfall totals have been even more extreme; for example, we’ve seen numbers close to 17.7 inches near Laytonville and over 15 inches near Honeydew.
**Interviewer:** Those are staggering amounts of rain. Looking ahead, what should residents expect as the storm continues to progress?
**James White:** We are predicting more rainfall throughout the weekend, with additional totals of one to two inches possible in many areas. The National Weather Service is particularly concerned about the risk of flooding and landslides given the prolonged nature of the rain. Also, as the storm progresses to the Sierra Nevada, we expect snowfall at elevations above 6,000 feet, which could add one to three inches of snow through Tuesday.
**Interviewer:** It sounds like a precarious situation for many communities. You mentioned the potential for landslides and downed power lines. How should residents prepare for these hazards?
**James White:** Preparation is key during these events. Residents in flood-prone areas should be aware of their surroundings and have an emergency plan in place. It’s also important to stay informed through local alerts and weather updates. We advise against travel unless absolutely necessary, as road conditions can rapidly worsen due to flooding and trees downed by strong winds.
**Interviewer:** Thank you for those insights, James. As this is the first major rainmaker of the season, what does this mean for the rest of California as we move further into winter?
**James White:** This storm is a reminder of the intense winter conditions we can experience here in California. It sets the stage for more frequent atmospheric rivers and storms, which can lead to both beneficial rainfall for our water supply and hazardous conditions. It’s important for residents to stay vigilant throughout the season.
**Interviewer:** Thank you, James, for sharing your expertise today. We appreciate your insights into this critical weather event.
**James White:** Thank you for having me. Stay safe out there!
**Interviewer:** That was meteorologist James White discussing the current atmospheric river impacting Northern California. Please stay tuned for more updates and advice from local authorities regarding this ongoing situation.
