The Bay Area is preparing for the second atmospheric river storm to soak the region this rainy season and alleviate the dire drought conditions in Northern California. There will be a slight chance of rain on Friday night into Saturday morning, with less than 0.10 of an inch forecasted in the North Bay, according to the National Weather Service.
Another series of storms is set to sweep through the Pacific Northwest and Northern California into next week and not only bring much-needed rain and mountain snow but also flooding concerns.
A dip in the jet stream across the Bering Sea through the northern Pacific Ocean will push waves of energy toward the Canadian Rocky Mountains and Northwest this week, according to AccuWeather Lead Long-Range Senior Meteorologist Paul Pastelok, who added that temperatures will be near to below normal.
Federal forecasters estimate that the atmospheric river storms that hit parts of northern and central California from October 23-26 dropped 7.6 trillion gallons of rain — which can also be expressed as 7,600,000,000,000.
“That’s enough water for over 244 million people for an entire year,” the National Weather Service’s Western Region Headquarters in Salt Lake City said in a statement.
On the Earth’s surface, the end of a drought is usually obvious. Rainfall arrives, streams and rivers increase in volume or begin to flow again, vegetation perks up, and parched soils regain their moisture. But what about below the earth’s surface? In particular, how does groundwater respond to the end of drought? Given the critical role that groundwater plays in many regions as a source of water for drinking and irrigation, understanding the effects of droughts on aquifers could help shape management decisions regarding these key resources.
The parade of storms that blasted California over the past week marked a strong start to the rainy season. Some parts of the state, including Napa, Santa Rosa and Sacramento, received half the rain in 24 hours that they got in all of the past year.
But with California locked in one of its worst droughts in modern history, and some areas short two years’ worth of water, a lot more wet weather is needed to mend the state’s water woes.
After nearly a year without rain, a series of potent Pacific storms are directed at Northern California this week, potentially bringing as much as a foot of rainfall and up to three feet of snow in the Sierra Nevada.
Multiple storms are expected to march into the West Coast this week, bringing along a changeable mixture of rain, wind and snow for many places. While a dent in the ongoing drought is expected, it will come at a cost.
This week has already kicked off with a storm marching into the Pacific Northwest. The grey skies and spits of rain that are typical of autumn led to a dreary end to the weekend along the Interstate 5 corridor across western Washington, Oregon and even Northern California.
The wet winter the American south-west has hoped for as it battles extreme drought and heat is increasingly unlikely to materialize as scientists now predict that a phenomenon known as La Niña will develop for the second year in a row.
The weather system could intensify the worst effects of the drought that much of the region already finds itself in, including higher wildfire risks and water shortages through 2022.
Though it’s unclear what the effects of the La Niña climate expected this winter will be for Northern California, drought-ending rain is likely not among them.
The climate pattern brought on by cooler-than-usual surface water in parts of the Pacific Ocean creates varying weather globally, but historically the phenomena has meant drier conditions in the southern part of the state and wetter conditions in the Pacific Northwest.
The Center for Western Weather and Water Extremes, or CW3E, at Scripps Institution of Oceanography, released its report October 11 on atmospheric rivers during Water Year 2021.
The report, “Distribution of Landfalling Atmospheric Rivers over the U.S. West Coast During Water Year 2021: End of Water Year Summary” shows that more atmospheric rivers landed on the U.S. West Coast in Water Year 2021 than in Water Year 2020. But the majority of those storms reached the Pacific Northwest, not California, where drought conditions have impacted water supply.
“The report on atmospheric rivers shows the variability in weather across the state from year to year,” said Jeff Stephenson, Water Resources Manager with the San Diego County Water Authority. “Through our partnership with CW3E and the AR forecasting tools they’ve developed, it better prepares us in management of our water resources using regional storage. This storage, in conjunction with developing multiple water supply sources in the San Diego region, has prepared us for years when rainfall levels are below normal in the region.”
Water Year 2021 experienced a total of 69 landfalling ARs over the U.S. West Coast, 4 more than Water Year 2020.
• While WY 2021 experienced more ARs, a much larger majority of the ARs only impacted the Pacific Northwest.
• California only experienced AR conditions (IVT >250 kg m–1 s–1) from 36 separate ARs during WY 2021, compared to 43
during WY 2020.
Distribution of Landfalling Atmospheric Rivers over the U.S. West Coast During Water Year 2021: End of Water Year Summary. Graphic: Center for Western Weather and Water Extremes
The lack of AR activity over California for two consecutive water years has resulted in a substantial lack of precipitation.
• A large portion of California received <30% of the normal precipitation for both Water Year 2020 and 2021.
• Coastal Washington and Oregon was the only location in the Western U.S. to receive near or above normal precipitation
during both water years, which is also the region that received a majority of the AR activity.
The San Diego County Water Authority partnered with the Scripps Institution of Oceanography, Center for Western Weather and Water Extremes, at UC San Diego in 2020 to better predict atmospheric rivers and improve water management before, during, and after those seasonal storms. The Center and its partners share best practices in forecast-informed reservoir operations, increased research around atmospheric rivers and droughts, and develop strategies for mitigating flood risk and increasing water supply reliability.
For additional details and graphics go to: https://bit.ly/3mKhkcR
