### Intense Storms Pummel Northern California, Setting Rainfall Records and Raising Flood Concerns

Northern California is currently grappling with heavy rainfall and significant snowfall in the Sierra Nevada, triggering flooding and potential mudslides. This weather system, the first significant rain event of the season, developed into a bomb cyclone due to rapid intensification before making landfall. Since then, it has moved southward, leaving its initial impact on the northern part of the state felt on Wednesday and Thursday.

On Thursday, Ukiah recorded a remarkable 3.66 inches of rain, surpassing its previous record from 1977 by half an inch. Meanwhile, Santa Rosa Airport experienced an astounding 4.93 inches of rainfall on the same day, shattering its previous daily record of 0.93 inches set in 2001. Humboldt and Mendocino counties saw the highest rainfall totals, with 17.7 inches near Laytonville and around 15 inches near Honeydew in the King Range mountains, according to James White from the National Weather Service in Eureka.

Over the weekend, Northern California is expected to receive an additional one to two inches of rain. Whiskeytown in Shasta County received 12.21 inches, while Sims in the Klamath Mountains recorded 13.37 inches, as noted by Bill Rasch from the NWS Sacramento office. The region could still see another one to two inches of rain, with some interior Northern California foothill areas potentially receiving between two to five inches. Snowfall is expected to begin after Friday, likely accumulating between one and three inches at elevations above 6,000 feet by Tuesday. Rasch emphasized that Friday would be the last significant day of rain for the region.

A Friday morning forecast from the Weather Service highlighted risks of prolonged rainfall, including increased chances of flooding, landslides, and downed trees and power lines in the North Bay. In the San Francisco Bay Area, the brunt of the rain has mainly affected Sonoma, Marin, and Napa counties, reported Dylan Flynn from the National Weather Service Monterey office. Santa Rosa encountered historical rainfall, smashing its three-day record of roughly 10 inches set in October 2021. This amount of rainfall is unprecedented in the past 123 years for the area.

The storm is expected to taper off in the North Bay and extend to the rest of the San Francisco Bay Area on Friday, potentially dropping one to three inches before diminishing on Saturday. The system might then move further south, affecting the Central Coast and possibly Southern California.

Come Saturday, Los Angeles and Ventura counties could see anywhere from a tenth to a third of an inch of rain, while parts of San Luis Obispo and Santa Barbara counties may receive up to an inch. According to the latest forecast from the NWS in Los Angeles, a second round of rain expected on Sunday could be slightly stronger but still falls under the "beneficial rain" category.

For Southern California, the likelihood of flooding or significant issues is low, though wet roads could possibly complicate traffic. In Rancho Palos Verdes' Portuguese Bend landslide region, increased rainfall is a concern due to its potential to aggravate ongoing land movement. However, Deputy Public Works Director David Copp highlighted efforts like improved drainage and stabilization projects aimed at minimizing new rain impacts.

Despite some recent slowing and stabilization in parts of the landslide zone, additional rainfall remains a potential threat to this vulnerable area.