Southern California is preparing for a dramatic weather shift this week, transitioning from unseasonably hot temperatures and strong Santa Ana winds to widespread rain, cooler conditions, and potential thunderstorms. The National Weather Service anticipates localized flooding, debris flows near recent wildfire burn scars, hazardous driving conditions, and coastal erosion across the region. Heaviest precipitation is expected Wednesday night into Thursday morning.
Much of the region, from southern Santa Barbara County across Ventura and most of Los Angeles County, can expect between half an inch and 1.5 inches of rain, according to Carol Ciliberti, a meteorologist with the National Weather Service in Los Angeles/Oxnard. Higher totals, between 1.5 and 3 inches, are forecast for south-facing mountains and foothills within this area. Specifically, Ms. Ciliberti indicated that Los Angeles International Airport could see just over an inch of rain, with about 1 inch in Oxnard and 1.3 inches in Santa Barbara.
Farther south, rain could begin in Orange and San Bernardino counties as early as Wednesday morning, spreading by the afternoon and evening. Sam Zuber, a meteorologist with the National Weather Service in San Diego, stated that mountains in the southern region could receive about an inch. Coastal Orange County and the Inland Empire are forecast for approximately three-quarters of an inch, with similar amounts for parts of northern San Diego County. Downtown San Diego might see about a half an inch within a 48- to 72-hour timeframe.
There is a 30 percent to 40 percent chance of thunderstorms in the Los Angeles/Oxnard forecast area, which could bring dangerous lightning, heavy downpours, and small hail. These conditions also carry the risk of waterspouts that could move onshore as weak tornadoes. Ms. Ciliberti noted that "shorter term, 15- to 30-minute heavy showers" often deliver significant rainfall in a brief period during these types of storms. A slight chance of thunderstorms is also present Wednesday night into Thursday morning across Orange, Riverside, San Bernardino, and San Diego counties.
Recent wildfire burn areas are particularly vulnerable to the approaching rain. The National Weather Service warns of a minor risk of flood and debris flows in these areas, with a 10 percent chance of heavier rainfall rates leading to more significant events near recent burn scars. Along the coastline, the combination of elevated surf and higher tides, brought on by an approaching full moon, could contribute to minor to locally moderate coastal flooding and erosion.
The storm's arrival coincides with ongoing stabilization efforts for a damaged hillside beneath Pacific Coast Highway near Laguna Beach, close to Crystal Cove State Park. A large crack on the bluff has prompted Caltrans to close one southbound lane. Crews are covering the hillside with plastic tarps, and Caltrans plans to place large boulders at the slope's base and develop a long-term stabilization plan. The potential impact of the approaching storm on this damaged hillside remains uncertain.
Additionally, the timing of the heaviest rainfall, particularly Wednesday afternoon and Thursday morning, could create problems for Southern California commuters. Ms. Zuber warned that heavy rain could reduce visibility and urged drivers to slow down, increase space between vehicles, and allow extra time for travel. Ms. Ciliberti also advised residents to prepare for possible localized flooding, especially if their properties have experienced drainage issues, emphasizing the need to "watch out for localized flooding" and to "slow down because the roads could be slick" due to lower visibility.
This storm represents a sharp reversal from last week's weather, which featured warm temperatures and heightened fire danger due to Santa Ana winds. Temperatures will continue to fall through midweek, with many coastal and valley communities seeing readings in the 60s and 70s by Wednesday and Thursday. Despite the dramatic shift, forecasters characterize these changing conditions as typical for fall in Southern California. Ms. Ciliberti described it as "a pattern change. It is fall," while Ms. Zuber noted that October frequently brings alternating periods of wet weather and dry Santa Ana wind conditions, stating, "This is not abnormal for this time of year at all." She added that "We start to see our winter storms coming down now." Unlike colder winter storms, this approaching system is expected to be relatively warm, with no snow forecast at higher elevations. Ms. Zuber referred to it as "just going to be a nice wetting rain." The storm is projected to move out of the region by Friday, making way for drier weather and sunshine. Temperatures are expected to rebound over the weekend, at which point another round of Santa Ana winds could develop, according to the weather service.