An incoming bomb cyclone is expected to hit the San Francisco Bay Area and the surrounding region on Wednesday before sweeping south, with forecasts warning that up to 10in of rain is possible in coastal mountain regions. Areas that will see lower rainfall, could still be disastrously affected due to the unfortunate timing and the compounding effect of the consecutive set of storms.
The NWS issued a warning for the risk of excessive rainfall impacting roughly 5 million people across the northern and central California, as agency meteorologists cautioned all who lay in the path of the “truly brutal system” to be prepared.
The impacts could include, “widespread flooding, roads washing out, hillsides collapsing, trees down (potentially full groves), widespread power outages, immediate disruption to commerce, and the worst of all, likely loss of human life”, according to a NWS Bay Area’s meteorologist, who wrote in a discussion on Monday that “this will likely be one of the most impactful systems on a widespread scale that [they had] seen in a long while”.
Pretty spectacular satellite imagery today of rapidly strengthening (“bomb”) cyclone out over the Pacific. This is the system that will bring widespread high wind and heavy rain to Northern California tomorrow, along with considerable risk of flooding/wind damage. #CAwx #CAwater
The historic storm broke levees in Sacramento county, submerging thousands of acres and stranding dozens of drivers who were caught in the deluge. Evacuations were ordered for two impacted communities and the Cosumnes River reportedly reached its highest level in history.
San Francisco, which recorded its second wettest day last weekend, also saw widespread flooding after more than 5in of rain hit the city. To the south, two separate sinkholes swallowed cars. By Tuesday morning, roughly 23,000 people were still without power across the state as officials raced to get impacted systems back up and running during a day of dry reprieve.
Officials confirmed Sunday that one person was discovered dead in a submerged car in Sacramento county. Another, to the south in Santa Cruz, was killed by a fallen tree. The NWS cautioned that, with conditions expected to escalate through the week, more life-threatening dangers loom.
A flood watch remains in effect with high risks from “extensive street flooding in portions of the Bay Area and Central coast”, the NWS said in a forecast discussion, adding that “these conditions will also lead to an increased threat for widespread shallow landslides”.
Along with the hazards, the heavy drenching will also deliver a solid dose of moisture for the drought-stricken state, but experts said the deluge will not be effective at combating long-term dryness. Even with a solid dump of snow at higher elevations – which helps replenish water systems during drier times – getting bursts of strong precipitation is far less helpful than lighter rains over longer periods.
“The significant Sierra snowpack is good news but unfortunately these same storms are bringing flooding to parts of California,” the director of the department of water resources Karla Nemeth said in a written statement issued with an update on the latest snow survey, which found levels were 177% of average before the big incoming storm. “This is a prime example of the threat of extreme flooding during a prolonged drought as California experiences more swings between wet and dry periods brought on by our changing climate.”
Last year showed a similar pattern, with a promising start that led into a long stretch of dry days. Weather whiplash, when strong rains delude parched systems, does less to aid in recovery, especially when storms are severe and destructive.
“We don’t want to get all the rainfall to eliminate the drought all at once,” said the NWS’ Bann. “The fact we have multiple days of this and heavy snow in the mountains will help alleviate some of these concerns – but we have a long way to go.”
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