Evacuation warnings were set to go into effect across Los Angeles County on Thursday evening as an atmospheric river approached Southern California, bringing with it the potential to put an early end to fire season while also bringing fresh risks of flooding and mudslides. <\/p>\n
Under the storm scenario deemed most likely by forecasters, downtown L.A. would see 2.62 inches of rain Thursday through Sunday, according to the National Weather Service. However, the forecast remains unsettled and varies widely.<\/p>\n
There\u2019s a roughly one-in-four chance of lower-but-still-notable precipitation, in the neighborhood of 1.39 inches, but an equal chance of a far-more-potent soaking of 4.81 inches over the same time period. <\/p>\n
Either way, as far as fire season is concerned, \u201cthis will certainly help,\u201d said Ryan Kittell, a meteorologist with the National Weather Service office in Oxnard.<\/p>\n
\u201cIf we do end up getting the rainfall that we expect, this will certainly get us close to the end of the fire season,\u201d Kittell said, and give Southern California a real buffer against a potential Santa Ana wind event. <\/p>\n
That would be a far cry from last year, when Southern California grappled with a record dry streak<\/a> over the fall and winter that left vegetation withered and primed to burn. Those \u201coff the charts\u201d conditions,<\/a> combined with exceptionally erratic<\/a> Santa Ana winds, fueled the rapid spread of the Eaton and Palisades fires, which rank among the deadliest and most destructive in California history. <\/p>\n Meteorologists say that Southern California needs 3 to 4 inches of widespread rain in the lower elevations for the high fire season to end. Downtown L.A. has already received 1.41 inches, almost all of it from just one stormy day in October. <\/p>\n Last year, downtown L.A. saw just 0.07 inches of rain from the start of October through mid-November. By Jan. 7 \u2014 the day the Eaton and Palisades fires roared to life<\/a> \u2014 downtown had only received a cumulative 0.16 inches. It wouldn\u2019t be until February, well after the blazes had already devastated Altadena, Pacific Palisades and Malibu, that the region saw enough rain to bring fire season to a close. <\/p>\n But the silver lining of the upcoming storm also carries a touch of gray. Rain of this magnitude could trigger damaging flows of mud and debris.<\/p>\n Evacuation warnings are in effect from 6 p.m. Thursday through 11 a.m. Sunday in areas near recent burn scars, due to the risk of mud and debris flows. This includes areas near the Palisades, Eaton, Kenneth, Sunset and Hurst fires that burned in January\u2019s firestorm<\/a>.<\/p>\n There are many reasons California has faced extraordinary fire risk in recent years. Climate change<\/a> has fueled increasingly extreme heat, withering shrubs and grasses. Residential development has increased in fire-prone wildlands. Power infrastructure<\/a> and failure to extinguish an arson-caused fire<\/a> have been the suspected culprits behind recent devastating blazes. <\/p>\n All this heightens the stakes of California\u2019s already delicate year-end dance between the Santa Ana winds<\/a> \u2014 the strength and heat of which have turbocharged many a fire \u2014 and the arrival of the rainy season. <\/p>\n The expectation for this autumn was considered grim with the return of La Ni\u00f1a in the central and eastern Pacific Ocean. Californians commonly think of La Ni\u00f1a, a natural climate pattern involving cooler sea surface temperatures, as a herald of drought, and the sibling El Ni\u00f1o pattern as synonymous with wet winters. <\/p>\n There\u2019s a reason for that. California saw epic rains during a significant<\/a> El Ni\u00f1o in 1982-83. Another in 1997-98 coincided with massive flooding all over the West Coast, as well as L.A.\u2019s wettest February on record. That was followed by a strong<\/a> La Ni\u00f1a in 1998-99, which was very dry. <\/p>\n More recently, 2020-21 and 2021-22 were both La Ni\u00f1a seasons, and were drier than normal for downtown Los Angeles. <\/p>\n But using La Ni\u00f1a as your only crystal ball can prove spectacularly disappointing<\/a>. As noted<\/a> by meteorologist Jan Null, two of California\u2019s costliest flood seasons \u2014 2016-17 and 2022-23 \u2014 were during La Ni\u00f1as.<\/p>\n This week\u2019s rains are not a definitive sign that the rest of this autumn and winter will be especially soggy. A number of La Ni\u00f1as have gotten off to wet starts only for the storm door to suddenly shut, according to Kittell. <\/p>\n There continues to be uncertainty regarding how intense this storm will be for Southern California, though expected rainfall totals have been rising as the system approaches. <\/p>\n Forecasters expect two peaks for the L.A. area \u2014 Thursday night into early Friday, and on Saturday, Kittell said. But it will still likely rain on Friday throughout the day and night. <\/p>\n The highest certainty of rain for Ventura County is Thursday night through Saturday night, and for L.A. County from Friday morning through Saturday night. There\u2019s also a 10% to 20% chance of thunderstorms Friday night and Saturday during the day, with a remote risk of localized damaging winds and even a tornado, the weather service said. <\/p>\n \u201cWe wouldn\u2019t be surprised if we hear a report of a tornado or two if that higher-end scenario plays out for Saturday,\u201d Kittell said. <\/p>\n