Days after California was hit by its “most impressive storm in nearly 20 years,” the state – fully saturated in many places – is gearing up for another series of atmospheric river events this weekend, with flooding, hail, powerful gusts of wind and even possible funnel clouds in places.
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Another round of torrential rains is falling on Saturday in the Golden State, where extreme drought fueled by the climate crisis has given way in recent weeks to massive flooding amid a catastrophic sequence of very wet atmospheric rivers – long, narrow regions in the atmosphere that transport moisture for thousands of miles. Recent storms have killed at least 18 people and left tens of thousands without power.
More than 25 million people are again under flood watch over much of California’s central coast as well as the Sacramento and San Joaquin valleys. While this weekend’s rainfall totals will be lower than previous storms, the flood threshold is also much lower as the ground is fully saturated in many areas.
“This atmospheric river is more progressive than some of the other atmospheric rivers that have occurred in recent weeks, which should help limit the extent of flooding potential,” said the Weather Prediction Center. “Everything that has been said applies to almost all of California; from the coast and both the Shasta and Sierra Nevada south to the Transverse Range, they have soil moisture percentiles greater than 95%.
“Parts of the state have collected 15-20+” of rain and more than 600% of normal rainfall over the past two weeks, they added.
And unfortunately, the chances of rain don’t stop there: the next storm will bring new chances of rain and flooding across much of the state from Sunday afternoon to Monday morning before finally settling into drought next week.
“A more intense surge of moisture is expected Saturday ahead of a stronger Pacific storm system that will move inland throughout the day,” the forecast center said. “There is a broad, small risk of excessive precipitation both in northern California, where rainfall will continue from Friday, and in the higher Sierra regions.”
Rain and snow are also forecast to spread across the Pacific Northwest and Western Intermountain West from Saturday through Sunday.
Common rainfall totals on Monday will be 2 to 3 inches along the coast and interior valleys, with 4 to 6 inches possible in the San Francisco Bay Area and the nearby Santa Cruz and Santa Lucia Mountains. This is likely to lead to several instances of flooding, mudflows, rockfalls and landslides.
“Rain is assured with a 100% probability of rain across the area, and with expected deep moisture and heavy rainfall, flooding is becoming a problem again,” the San Francisco office of the National Weather Service said.
San Francisco has already recorded one of the 15 wettest winters on record, with more than a month left. If it gets 4 to 6 inches of rain over the next three days, the city will easily top the top five.
Slight Risk of Excessive Rain – Grade 2 of 4 – Alert in effect mainly due to extremely wet conditions preceding projected rainfall and leading to increased flood fears.
“Forecasted soundings showed some instability over the Central Valley behind the front Saturday afternoon and evening, with hail expected to accompany stronger thunderstorms and possibly funnel clouds,” the Sacramento weather services office said.
River flooding is also a big problem, especially around the Russian River in northern California and the Salinas River near Monterey. “Plan for additional disruptions to travel and mountain recreation over the weekend as periods of heavy snowfall return to the Sierra,” the Reno weather service office said.
Very heavy snowfall is also forecast for the Sierra, with 1 to 2 feet expected on Saturday and an additional 2 to 3 feet on Monday. “The heaviest snowfall will be on Saturday and Monday, with less heavy snowfall in between,” the Reno weather services office said.
Strong winds will also accompany this system, gusting up to 40 to 50 mph in the Sacramento Valley and up to 60 mph in the mountains. This can lead to fallen trees and power lines being placed in the currently very saturated soils.
“The system will pack a decent amount of southerly winds, and strong winds are in place in the mountains of San Luis Obispo and Santa Barbara counties – the same strong winds will move into Ventura and LA counties Saturday evening,” the Los Angeles office reported.
The good news is that by the end of the week, much drier conditions are forecast across California, allowing the ground to dry out and river levels to drop.
“It’s been a long time since Californians enjoyed an extended below-average precipitation forecast,” CNN meteorologist Brandon Miller told CNN. “But after the last three weeks, it definitely is.”