26 Jan 2021 | 03:25 PM UTC
US: Adverse weather forecast across portions of California through at least early Jan. 29
Heavy rainfall, strong winds, and possible flooding forecast across California, US, through at least Jan. 29. Disruptions possible.
Event
Rounds of heavy rainfall, strong winds, and possible flooding associated with a low-pressure system are forecast to occur across portions of central and southern California, US, through at least early Jan. 29. The Weather Prediction Center (WPC) has issued a "Moderate Risk" for excessive rainfall for coastal western Monterey and San Luis Obispo counties. Additionally, a "Slight Risk" for excessive rainfall for Sonoma, Napa, and Marin, far western Yolo, northwestern Solano, San Mateo, Santa Cruz, southern Alameda, southern San Joaquin, Santa Clara, southwestern Stanislaus, far southern Merced, Monterey, San Benito, far southern Fresno, western San Luis Obispo, Santa Barbara, and central Ventura counties, where the heaviest rainfall is forecast. Additionally, the National Weather Service (NWS) has issued flash flood watches for portions of coastal west-central California. Officials could update and possibly extend the coverage of the relevant weather alerts over the coming days.
As of early Jan. 26, authorities have issued evacuation orders and evacuation warnings for portions of San Mateo and Santa Cruz counties. Emergency shelters for displaced residents are located at San Lorenzo Valley High School in Felton, Scotts Valley Community Center in Scotts Valley, and Pacific Elementary School in Davenport.
Hazardous Conditions
The storms will be capable of producing heavy downpours and damaging winds across the affected area through at least early Jan. 29. Forecast models indicate rainfall accumulations of 20-30 cm (8-12 inches) are possible in central coastal California, where the "Moderate Risk" is in place. Widespread accumulations of 10-20 cm (4-8 inches) are forecast across central California. Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed or a lack of stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are possible in hilly or mountainous areas, especially where the soil has become saturated by heavy rainfall.
Authorities could issue mandatory evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are possible where significant flooding or landslides impact utility networks.
Transport
Floodwaters and debris flows could render some bridges, rail networks, or roadways impassable, impacting overland travel around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.
Severe weather could also trigger flight delays and cancellations at regional airports. Authorities may temporarily suspend port operations or close beach fronts along the Pacific Ocean if strong winds trigger hazardous sea conditions. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas that see heavy rainfall and potential track inundation. Localized business disruptions may occur in low-lying areas; some businesses might not operate at full capacity because of flood damage to facilities, possible evacuations, and some employees' inability to reach work sites.
Advice
Monitor local media for weather updates and related advisories. Confirm all transport reservations and business appointments before travel. Make allowances for localized travel delays and potential supply chain disruptions where flooding has been forecast. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.
