Atmospheric river to unleash deluge of rainfall across California this week
By late Tuesday, a moisture-filled pattern will start back up again along the West Coast, raising concerns for flooding from Central to Southern California.
AccuWeather Chief Meteorologist Jonathan Porter discusses the California rain and mudslide threat.
Following a brief lull in the stormy pattern, California residents are on track to be doused by another atmospheric river, AccuWeather meteorologists warn. Through early this week, the drier stretch will persist across much of the West coast; however, the next big weather-maker will arrive by late Tuesday night into Wednesday for places along the Central and Southern California coastline.
"California will be impacted by yet another atmospheric river this rainy season, delivering moisture to areas that have seen little of it this year," noted AccuWeather Meteorologist Jacob Hinson.
Hinson added that since Oct. 1 of last year, places like Fresno, California, have only recorded about 56% of their historical average rainfall. Locations farther south like Los Angeles are facing lower statistics, with only 22-32% of their typical rainfall recorded during that time frame.
Push of Arctic air early week
Ahead of the storms this week, forecasters say that a push of Arctic air will pulse southward out of Canada into the Northwest, challenging some daily overnight low records. During the coldest part of the week; however, conditions are expected to be mainly dry across the Pacific Northwest as storms may not reach that far north along the West coast until late week.
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Cities like Portland, Oregon, are forecast to have low temperatures ranging into the mid-20s Fahrenheit from early to midweek, roughly 10-15 degrees F below typical February minimum temperatures and approaching daily record lows.
Early Tuesday morning, AccuWeather RealFeel® Temperatures will trend even lower into the teens along the Washington and Oregon coastline. Farther inland, RealFeel®'s ranging in the single digits will be commonplace from Bend, Oregon, to Nampa, Idaho, located to the west of Boise.
Deluge of rain on the way for California
While the initial raindrops may arrive along the Central Coast and San Francisco Bay area by Tuesday, the primary push of moisture into the state may be late Wednesday night through Thursday.
"This atmospheric river will bring with it multiple inches of rain from the North Bay Area all the way down the coast to San Diego. For coastal areas, there will be a small amount of rain impacting from the South Bay Area down the coast to Point Conception overnight Tuesday, which then continues through Wednesday morning. The main event will be impacting sometime Wednesday night through Thursday morning," noted Hinson.
"Most areas will see 1-2 inches of rain from early Wednesday morning through Friday night. Typical upslope areas could see as much as 2-3 inches for the duration of the event," warned Hinson.
However, locally, much higher amounts can occur in the south-to-southwest-facing slopes of the coastal foothills and mountains with an AccuWeather Local StormMax™ rainfall of 11 inches.
Blizzard conditions possible for mountain locations
Hinson added that a decent amount of rain will be impacting the Sierra as well, dumping 2-4 inches of rain on the Foothills and 6-12 inches of snow along the range. Some areas of the mountains could receive up to 24 inches of snow, and with winds gusting to 40 mph on Thursday, blizzard conditions across the Sierra are not out of the question.
Travelers along portions of Interstate 80 through Donner Pass could face significant delays, particularly later this week, as snow spreads through the mountains.
In addition to the gusty winds in the mountainous terrain later this week, spots along the coast will have a chance to gust upwards of 25-35 mph at times Wednesday afternoon into early Thursday. Offshore winds can be even stronger, and mariners from Northern California to Point Conception should stay weather aware and pay mind to local advisories before taking to the seas.
Flooding concerns will be heightened across the region, not only for locations expected to receive over 2 inches of rainfall this week but for burn scar areas in Southern California recently impacted by the devastating fires over the last month.
"While this rain will be beneficial to areas like the Central Valley and L.A. Basin, it could be too much of a good thing in certain areas. We’re still concerned about burn scars getting enough rainfall to affect soil stability, thus causing landslides or debris flows. The amount of rain in the forecast can also cause issues where drainage systems aren’t adequate, causing localized flooding of streets and roadways," Hinson said.
Can Las Vegas break its dry streak?
The last time Las Vegas recorded more than a trace of rain dates back over 200 days, to the middle of July 2024. The upcoming pattern may finally allow them to break their streak and bring measurable precipitation to the region.
Portions of southern Nevada are currently facing levels of exceptional drought, according to the U.S. Drought Monitor. Later this week, as moisture advances across Southern California and into the desert regions of the Southwest, forecasters say that chances are increasing for a round of rain or showers to spread into Las Vegas.
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