Swell Matrix

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard Ca

402 am PDT Fri Sep 18 2026

Synopsis

17/740 PM.

Slight warming and a shrinking marine layer are expected Friday into the weekend. Temperatures will cool by a few degrees Sunday and Monday, then another gradual warming trend is likely through at least the middle of next week.

Short Term

(tdy-Sun), 18/142 AM.

Fairly benign conditions expected through the weekend. No hazard products expected. Warmest on Saturday, pushing close to 90s for some valley locations especially Salinas and Antelope Valleys. Marine layer stratus may return to portions of the LA Basin on Sat, and more likely on Sunday. There is potential of AM clouds reaching into San Gabriel/San Fernando Valleys on Sunday.

Long Term

(Mon-Thu), 18/214 AM.

A small trough moves into the area late Sunday into Monday. Interestingly enough, this feature is mostly expected to move eastward following the upper level flow, but a weaker portion is expected to split and become stationary, centering itself over the inner coastal waters by mid-week. This puts LA/VTA counties in a relatively favorable position for the influx of moisture and instability. However, confidence is low if these parameters along with lift will be sufficient enough for even a slight mention of showers and thunderstorms across the area. Details at this time are blurry, but the weak signal is strongest across typically favored mountain areas this time of year. Temperatures will warm some across the area, and humidity will increase some over the LA Basin.

Aviation

18/1101z.

At 0806Z at KLAX, the marine layer was 4000 ft deep. The top of the inversion was at 5000 ft with a temperature of 17 C.

High confidence in VFR TAFs for desert airfields (KPMD & KWJF).

For KPRB, KSBP, & KSMX: timing of CIG/VSBY restrictions may be off +/- 3 hrs and flight minimums by one category.

KLAX, Moderate confidence in TAF. Return of MVFR CIGs 015 (+/- 300 ft) should be accurate within +/- 2 hrs of fcst. No significant east wind component expected.

KBUR, Moderate confidence in TAF. No wind issues expected.

Marine

17/822 PM.

Moderate confidence in fairly typical Small Craft Advisory (SCA) northwest winds across the outer waters south and southwest of Point Sal, then higher confidence in more widespread SCA winds Friday afternoon through Sunday across the outer waters and nearshore waters along the Central Coast. Choppy, short period seas will develop.

Across the Santa Barbara Channel, there is a 30-40% chance of SCA winds Friday afternoon and evening, then a 40-60% chance Saturday and Sunday in the afternoon/evening hours. Local gusts near 20 knot will be common each afternoon and evening through the San Pedro Channel and Santa Monica Bay.

Watches, Warnings, Advisories

Ca, NONE. PZ, Small Craft Advisory in effect from 3 PM this afternoon to 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Sunday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Sunday for zones 673-676. (See LAXMWWLOX).

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