Southern California swings from Santa Ana winds and highs in the 80s to a 90%-plus chance of widespread rain from as early as Nov. 13

Southern California began the stretch with offshore Santa Ana winds and highs in the 80s, then faces a sharp reversal. The National Weather Service office in Los Angeles and Oxnard put the chance of widespread rain across the region above 90 percent, with the first drops possible as early as late Friday, Nov. 13. Cooling of about 10 degrees was expected to begin on Thursday.

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An earlier forecast had pointed to a single heavy storm on Nov. 15 to 17. By Nov. 9 the picture had changed to a series of upper-level lows with dry pauses between them, which lowers the odds of one dramatic downpour and raises the odds of a damp, drawn-out week.

Santa Ana gusts of 25 to 40 mph and highs in the 80s

The Los Angeles and Oxnard office’s forecast discussion of 5:39 a.m. PST on Nov. 8 described weak to moderate Santa Ana winds continuing overnight and each morning into midweek. Offshore pressure gradients of 3 to 4 millibars were expected to produce gusts of about 25 to 40 mph in the wind-prone corridor of Los Angeles and Ventura Counties, and the forecaster called for widespread 80s on the coasts and valleys, around 10 degrees above seasonal normals.

The weather service’s explainer on downslope winds describes the mechanism: high pressure over the dry desert Southwest pushes air toward low pressure off the coast, and the air warms as it compresses while descending the mountainsides. The season runs from September through May, and the dry air raises wildfire risk. That is why the same pattern that brings heat in November also brings fire-weather attention.

The 8:35 a.m. discussion on Nov. 9 put highs 10 to 15 degrees above normal through Wednesday and noted offshore flow continuing, with weak winds each morning and nothing near advisory levels.

A cooling trend and rain chances starting late Friday

By the Nov. 9 afternoon issuance, posted at 4:34 p.m. PST, Santa Ana winds were expected to strengthen slightly on Tuesday, pushing highs from the 80s to around 90 on coasts and valleys. A rapid cooling trend was set to start Thursday, with highs dropping about 10 degrees and returning to near normal by Friday.

The rain outlook in that text is built on probabilities. It put the chance of widespread rain across Southern California above 90 percent, with chances beginning as early as late Friday and continuing into the following week as at least three upper-level lows moved through. It also said there was at least a 50 percent chance of minimal amounts, under half an inch, through the middle of the following week, with dry breaks of one to three days.

From an inch-plus storm to minimal totals

The Nov. 8 discussion had raised a bigger possibility. It said a significant system with periods of heavy rainfall was possible, with 1 inch or more for the storm total, though some model solutions showed minimal rain, and it noted that totals had trended slightly higher with each update. The model runs at the time highlighted Sunday into the following Tuesday, Nov. 15 to 17.

The next day’s text moved the other way. The morning discussion on Nov. 9 said the storm was trending slower and more southerly, which lowered the chances of heavy rainfall rates and amounts, and it gave 30 to 40 percent chances of rain each day from Saturday through Monday. Forecast confidence was expected to improve by midweek.

High tides of 7.0 to 7.6 feet and flooding on west-facing shores

The coast faces its own hazards before any rain arrives. High tides peaking in the morning through Tuesday between 7.0 and 7.4 feet above the mean lower low water datum were forecast, and a west-to-northwest swell peaking Monday raised the risk of moderate coastal flooding on west-facing shores such as Oceano, Cayucos and the Ventura County coast. Forecasters said the tides would fall short of the record-setting ones two weeks earlier.

The office’s hazard map, updated at 7:08 p.m. PST on Nov. 9, listed tide levels of 7.1 to 7.6 feet for Ventura and Los Angeles, with surf of 6 to 9 feet in Ventura County and 4 to 6 feet in Los Angeles County, all in effect through noon on Tuesday.

When rain does arrive on burned or steep ground, the weather service’s flood safety guidance is blunt about water over a roadway: stay out of it on foot or by car, because the pavement underneath may already be gone.

The unresolved piece is the amount. A 90 percent chance of rain and a 50 percent chance of under half an inch can both hold at once, and the forecaster expected clarity on timing and totals by midweek. Until then, the practical range runs from a few damp hours between dry breaks to a soaking that approaches the inch-plus totals floated on Nov. 8, and the Los Angeles and Oxnard forecasters made clear that the models had not yet converged on either outcome.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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