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Critical Infrastructure Impacts from Atmospheric River in California, Where another Episode is Expected this Week (Updated January 17, 2023)

Critical Infrastructure Impacts from Atmospheric River in California, Where another Episode is Expected this Week (Updated January 17, 2023)

Created: Tuesday, January 17, 2023 - 12:30
Emergency Response & Recovery, Natural Disasters

January 17, 2023

Forecasters believe the weather system fueled by atmospheric rivers that has brought heavy rain and flooding to California the past few weeks is finally easing. In the meantime, a ninth atmospheric river impacted the state over the weekend and another is expected to hit midweek, although it is expected to be relatively mild.

The latest system was relatively weak compared with earlier storms, but flooding and mudslide risks remained because the state was so saturated. Mountain areas experienced some of the greatest effects, particularly in the northern Sierra Nevada’s where heavy snow led to highway closures due to whiteout conditions. Mountain areas in Southern California were under winter storm warnings and advisories, where many roads remained impassable because of mud and rockslides. Meanwhile, downtown Los Angeles set a rainfall record Saturday with 1.82 inches. The weather that is expected to hit the state midweek “barely qualifies” as an atmospheric river, Michael Anderson, the state climatologist with California’s Department of Water Resources (DWR), said Monday. It is forecast to be confined mostly to Northern California when it makes landfall Wednesday. More long-term, forecasters are also concerned of the potential for springtime flooding given all the snow brough by recent storms. Ever mindful about California’s extreme drought, the DWR is partnering with the State Water Resources Control Board to fast-track efforts to capture flood waters to recharge groundwater basins. Read more at the Associated Press, the Washington Post, California DWR, and in the FEMA Daily Operations Briefing posted below.

January 12, 2023

Since late December California has experienced between seven and eight atmospheric rivers, whose heavy precipitation have brought damaging floods, landslides, and critical infrastructure impacts. There is a possible pause in sight, but not before more episodes of heavy precipitation.

An ongoing atmospheric river is mostly affecting Northern California, where FEMA reports river, creek, stream, roadway, and urban flooding are possible. Areas up and down the California coast are still recovering from ongoing and recent events, with at least two more atmospheric rivers on the way that will hamper recovery efforts. The first is forecast to surge into California over the weekend. Coastal areas over almost the entire state as well as the Central Valley could see another 1 to 3 inches of rain, including around the Bay Area, Sacramento, Santa Barbara, and Los Angeles. The second will affect California late Sunday into Monday or Tuesday. While it’s too early to pinpoint rainfall or snow totals, a general inch or two of rain can be expected in Northern California, with amounts probably waning farther south. So far, prolific rain totals of 10 to 20 inches have accompanied the promenade of storms, which are expected to continue until at least around January 20, when there could be a change. Read more at the National Weather Service, the Washington Post (articles one and two), the Associated Press, and in the FEMA Daily Operations Briefing posted below.

January 10, 2023

More than 34 million Californians – about 90 percent of the state’s population – are under a flood watch as an atmospheric river lingers and continues to bring heavy precipitation to areas much more accustomed to drought. Whereas much of the focus last week was on Northern California, this week communities in Southern California are increasingly affected, with the National Weather Service calling what’s being experienced there “the most impressive storm” since 2005.

The storm barreled into Southern California yesterday, forcing evacuations in numerous communities. It dumped more than 16 inches of rain in some areas and is expected to move through Los Angeles, Orange, and other counties today. Significant power outages are being reported in the area, with approximately 12,000 Los Angeles County customers without power as of this morning. Statewide, approximately 220,000 customers are without power, according to In terms of critical infrastructure, the most significant impacts appear to be in the transportation sector, in particular with numerous road closures due to flooding, debris and mud flows, and at least one sinkhole. Despite the rains, much of California remains in severe to extreme drought, though the storms have helped fill depleted reservoirs. The parched landscape has been less able to absorb all the rain, helping to facilitate the widespread flooding. The storms’ intensity and back-to-back nature have also been factors. “While some of the forecast rain totals are impressive alone, it is important to note that what really sets this event apart are the antecedent conditions,” the National Weather Service office in San Francisco said. “Multiple systems over the past week have saturated soil, increased flow in rivers and streams, and truly set the stage for this to become a high impact event,” it continued. The National Weather Service also notes nearly all of California has seen much above average rainfall totals over the past several weeks, with totals 400-600 percent above average values.

While the current episode of heavy precipitation across California is beginning to wind down, the National Weather Service reports another system is quickly gathering strength off the West Coast and heading once again toward the state. The core of the system is expected to slam onshore with moderate to heavy rain resuming across much of California today through tonight. Additionally, the National Weather Service reports an enormous cyclone forming well off the coast of will bring yet another atmospheric river toward the West Coast – this time impacting areas further north from northern California northward up the coast of the Pacific Northwest on Wednesday.

Read more at the National Weather Service, the Los Angeles Times, the Associated Press, and CNN (articles one and two), and in the FEMA Daily Operations Briefing posted below.

January 5, 2023

The latest large storm being fed by an atmospheric river is moving across California and bringing excessive rainfall, flooding, debris flows and landslides, high winds, and more. The situation is exacerbated by recent storms that saturated soil in many of the affected areas and more heavy rain is expected in the days to come.

In California, power outages were affecting over 180,000 customers as of this morning. In the transportation sector, there are multiple road closures due to flooding, mudslides, and damage. In San Benito County, located south of San Francisco, officials had earlier warned of the possibility that a dam that had already been compromised was going to be overtopped by water and that surrounding areas would flood. They issued evacuation warnings as a result. More recently, they have indicated the water is receding, although they added they will keep monitoring the situation as more rain is expected. Forecasters say more than 10 inches of rain could fall in some parts of Northern California over the next week. In addition to the current storm, they are watching other systems out at sea that could also hit the region with more precipitation. According to the National Weather Service, “another system with a stream of moisture will arrive late tomorrow into the weekend for [California].”

California Governor Gavin Newsom declared a state of emergency yesterday to allow for a quick response and to aid in cleanup from the storm that hit just days earlier. “We anticipate that this may be one of the most challenging and impactful series of storms to touch down in California in the last five years,” said Nancy Ward, the new director of the California Governor’s Office of Emergency Services. In San Francisco, which has up to 6 inches of rain in the latest storm, Mayor London Breed said the city is “preparing for a war.”

The storm is also impacting areas of Southern California. In Santa Barbara County,  evacuations were ordered for those living in areas burned by three recent wildfires, where heavy rain forecast for overnight could cause widespread flooding and unleash debris flows. Read more at USA Today, the Associated Press, Newsweek, KSBW News, and in the FEMA Daily Operations Briefing posted below.

January 3, 2023

Parts of Northern California are continuing to respond to and recover from an atmospheric river that impacted the area beginning early Saturday, bringing high winds and flash flooding that has significantly affected the energy, transportation, and dams sectors. Meanwhile, a large and powerful cyclone is brewing in the Pacific and forecast to bring another episode of heavy precipitation tomorrow.

Sacramento County has been one of the hardest hit areas, where approximately 165,000 customers were without power on Saturday evening (that number has since decreased to about 2,400 as of this morning). In addition, the heavy precipitation caused flooding on many roadways and resulted in the failures of two private levees. The events spurred evacuation and shelter-in-place orders for many residents. Parts of Nevada and Arizona were also impacted. And there’s more severe, dangerous weather to come. The National Weather Service (NWS) predicts the Sacramento region could see up to 3 inches of rain and gusts up to 50 mph, again producing a high risk of widespread power outages and flooding in low-lying areas. It has issued a flood watch, in place from early Wednesday through Friday morning for most of interior Northern California, including the entire Sacramento Valley. The NWS also said more systems are expected to bring “moderate to heavy” precipitation to Northern California this coming weekend through next Monday, with details still “uncertain.” Read more at the Sacramento Bee (articles one, two, and three) and in the FEMA Daily Operations Briefing posted below.