A furious storm unleashed from a “bomb cyclone” over the Pacific Ocean slammed ashore Sunday in drought-plagued Northern California, blasting a wide swath of the West Coast with heavy rain, damaging winds, flooding and mudslides.
Flooding across the San Francisco Bay Area closed streets in Berkeley and inundated the Bay Bridge toll plaza in Oakland. The National Weather Service in Sacramento warned of “potentially historic” rain for the city’s downtown.
“Debris flows are currently occurring and already causing road closures,” the weather service tweeted. “If you are near a burn scar, it may be too late to evacuate. Do not attempt to cross a debris flow. Take shelter in the highest floor of your home.”
A bomb cyclone forms when air pressure rapidly drops as the storm explosively strengthens. The storm was forecast to pound some areas with a foot of rain while dumping up to 8 feet of snow over the mountains, forecasters said.
“Conditions will continue to deteriorate as the system approaches,” the National Weather Service’s Weather Prediction Center warned in a tweet. “Strong winds, high surf, and heavy rain will lead to major impacts. Heavy snow in the Sierra starting tonight.”
The bomb cyclone was pulling deep tropical moisture from the Pacific, creating an “atmospheric river,” AccuWeather Meteorologist Jon Porter said. He described the phenomenon as a “firehose of moisture in the sky” capable of unleashing intense rain and mountain snow.
“Flooding, rock slides, chain controls, overturned vehicles – and that was just this morning,” the California Transportation Department tweeted Sunday. “This atmospheric river storm is expected to intensify with heavy rain and significant snow into tomorrow. Do NOT drive if you don’t have to.”
The region needs the rain. Gov. Gavin Newsom just last week declared a drought emergency for the entire state, citing three years of drought across the West.
Seventeen major wildfires are burning in California, Idaho, Montana, Oregon and Washington, according to the National Interagency Fire Center. Wildfires have burned almost 2 million acres in California in 2021 alone. The storms will effectively end the wildfire season in much of the region, AccuWeather’s Porter said.
“This rainfall is coming about a month ahead of average and will be very welcome in fighting the remaining fires, particularly in Northern California,” Porter said.
Moisture from the developing atmospheric river is taking aim at the northern and central portions of California as well as part of southern Oregon, with the greatest intensity from this morning to Monday, he said.
Rainfall of up to 2 inches an hour may come “too fast and too furious,” leading to serious flooding and mudslides that could threaten lives and property, Porter added.
The National Weather Service Bay Area issued flash flood watches, tweeting: “Main concern will be 2020 burn scars but urban and small stream flooding likely as the heavy rain band passes through Sunday afternoon and night.”
Snow will begin to fall at elevations above 8,000 feet, but then drop down to elevations around 6,000 feet by Monday, AccuWeather said.
“Given the amount of moisture aiming at the northern and central Sierra Nevada, there can easily be 60-100 inches of snow at levels above 8,000 feet,” AccuWeather Senior Storm Warning Meteorologist Rich Putnam said.
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