20 Mar 2023 | 05:57 AM UTC
US: Flooding ongoing across California as of late March 19
Flooding and evacuations ongoing across California, US as of late March 19. Further severe weather forecast.
Event
Flooding and evacuations are ongoing across California as of late March 19. California remains under a state of emergency after being impacted by a series of winter storms that have struck the state over recent days and weeks.
Evacuation orders remain in place for hundreds of people in Monterey County; the worst affected is the community of Pajaro, where a 37 meter (120 feet) breach in the levee along the Pajaro River late March 10 resulted in widespread flooding. Authorities have also issued evacuation orders for the community of Allensworth and Alpaugh in Tulare County and Airport Court in Manteca and Lathrop's Haven Acres Marina in San Joaquin County.
Authorities have confirmed significant structural damage across Mono County; the damage is likely to increase with additional rooftop snow loading. Crews in the county are removing snow and debris while repairing erosion on roadways to limit future damage. Reports indicate one fatality in Oakland, California, early March 10 due to a roof collapse and another two deaths in Placer and San Bernardino counties. A boat capsized in San Diego County late March 11; at least eight people died, and search and rescue operations are underway for the remaining missing people.
Government Advisories
Additional rain and mountain snow is forecast over California from March 21 due to another atmospheric river. As of late March 19, the National Weather Service (NWS) is maintaining winter storm and high wind watches across southern California. Winter storm warnings and watches are in place across northeastern parts of the state. Flood watches are also in effect for portions of central California.
Hazardous Conditions
The storms could produce rounds of heavy precipitation (including rain and snow), strong winds, and isolated thunderstorm activity in the affected area. Where precipitation falls as rain, flash and areal flooding is possible. Such flooding is possible in low-lying communities near watercourses and other large bodies of water, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites downstream of large reservoirs may be subject to flash flooding after relatively short periods of intense rainfall.
Precipitation could fall as snow in the higher elevations over the coming days. Wind gusts could cause blowing and drifting snow; decreased visibility is likely in mountainous areas. Rain-induced landslides cannot be discounted in areas of elevated terrain; there is also the possibility of avalanches in mountainous areas where the snowpack has become unstable due to heavy snowfall. Power outages are likely throughout the affected area.
Transport
Floodwaters and related debris may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around the affected area. Flooding in urban areas could also result in significant traffic congestion. Heavy snow will likely make driving hazardous in some areas; authorities could implement temporary road closures or detours in such locations. Mountain passes and tunnels could be closed as a precautionary measure during periods of intense snowfall.
The disruptive weather will likely cause some delays and cancellations at airports in the region. Authorities may temporarily suspend port operations along the Pacific coast if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding or snow could block regional rail lines; freight and passenger train delays and cancellations are possible in areas that see heavy rainfall and potential track blockages.
Disruptions triggered by inclement weather and resultant hazards, such as flooding or avalanches, could persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. If there is severe damage to infrastructure, repair or reconstruction efforts may result in residual disruptions.
Advice
Monitor local media for weather-related updates and advisories. Confirm all transport reservations and business arrangements before traveling in the affected area. Seek updated information on road conditions before driving or routing shipments through areas where severe weather is forecast; plan for possible supply chain disruptions throughout the affected areas. Stay away from elevated streams, creeks, and other watercourses that are prone to flash flooding. Do not attempt to navigate flooded roadways. Exercise caution in elevated terrain due to the threat of landslides, as well as mountainous regions where avalanches pose a threat. Charge battery-powered devices in the case of prolonged electricity outages.
