Swell Matrix

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard Ca

524 am PDT Tue may 17 2022


17/337 AM.

A persistent broad area of low pressure over the West will keep a northerly pressure difference across the state into Thursday and gusty northerly winds in place at times. While a marine layer will remain across the southern coastal areas and will keep temperatures near persistence at the beaches, a warming trend will develop away from the coast Wednesday and Thursday as weak high pressure builds in.

Short Term

(tdy-Thu), 17/258 AM.

Broad troughing will reinforce along the California coast this morning. A persistent northwest low-level will likely remain in place over the next couple of days, albeit weaker than the last several days. The low level flow will feed an eddy circulation and allow it to interact with the troughing digging down the state to deepen the marine layer some through tonight. Clouds will start to expand a little more across the South Coast of California as the eddy will remain intact over the coming days.

The trough axis will move over the region late tonight and shortwave ridging aloft will build in behind it. While the eddy circulation will remain in place, the shortwave ridge building into Central California will tighten the marine inversion. Many coastal areas south of Point Conception will struggle to clear Wednesday, and temperatures will remain on the cooler side of normal; however away from the coast and for the Central Coast, most areas will see temperatures will warm, and interior areas will warm well above normal as an offshore flow component establishes. For most South Coast beaches, the story will be one of May Gray over the coming days with clouds becoming well- entrenched across the southern California bight, a pattern very typically for this time of year.

Long Term

(Fri-Mon), 17/337 AM.

Deterministic solutions continue to indicate strong onshore trends developing for Friday and agree well with EPS ensemble members across the area. There are a few member solutions that indicate a warmer solution continuing and create a much wider spread for Friday, but a vast majority of the ensemble means trend toward the deterministic solutions. A +10 mb onshore push in the deterministic runs between KLAX-KDAG would produce gusty onshore winds out in the Antelope Valley, while very likely keeping the coastal and valley areas shrouded in clouds. NAM BUFR time height sections for KLAX double the marine layer depth between Thursday and Friday, quickly deepening it from around 1500 feet deep Thursday to near 3000 feet deep by Friday. The current forecast looks agreeable and no major tweaks were made. Low clouds and fog are likely to make a good push inland. EPS and NAEFS standardized anomalies suggest a strong westerly wind component toward Thursday afternoon and Friday morning, and this is reflected in some of the EPS ensemble members for wind gusts at KSDB, KPMD, and KWJF. Advisory level onshore winds remain a possibility for interior portions of the area.

The forecast after Friday get kind of muddled as a lot spread develop over the weekend between the EPS, GEFS, and CMC members. While the deterministic solutions want to develop a weak cut-off trough along the southern California coast, a shift of the pattern either 200 miles to the west or east will give quite different results. For the current time, the long term portion leans toward the NBM.



At 1105Z at KLAX, the marine layer was 1600 ft deep. The top of the inversion was around 3800 feet with a temperature of 18 C.

High confidence in desert TAFs, moderate confidence in all others. Timing of flight cat changes could be off by +/- 2 hours. There is 20% chance of brief IFR/LIFR at KPRB thru 16Z. There is a 20% chance that KOXR and KCMA remain VFR thru the 18Z. 40% Chance of BKN008 at KVNY and KBUR thru 16Z.

KLAX, Moderate confidence in TAF. Timing of flight cat changes could be off by +/- 2 hours. There is a 40% chance of an east wind component reaching 10 knots 10-15Z.

KBUR, Moderate confidence. Timing of flight cat changes could be off by +/- 2 hours. 40 percent chance of BKN008 thru 16Z.


17/339 AM.

An extended period of Gale force winds will be common through at least Thursday or Friday for the outer waters from the Central Coast to San Nicolas Island. This will create steep short period waves over all coastal waters through at least Thursday, with ample white caps for hazardous sea conditions.

For the nearshore waters along the Central Coast, Small Craft Advisory (SCA) level winds are likely each day through at least Thursday for the afternoon and evening hours.

For the Santa Barbara Channel, high confidence in SCA level winds confined to the western portion this afternoon and evening. Widespread steep waves likely. Winds are likely to remain below SCA level after tonight, however there is a possible of the extreme western portion reaching SCA levels at times.

For the Santa Monica Basin, San Pedro Channel, Orange County area, good confidence that winds will likely stay below SCA levels, with 10 to 15 kt westerlies each afternoon and evening across the western portion. Choppy seas likely each afternoon and night.

High confidence in all nearshore waters south of Point Conception will see moderate southeast winds each morning, with isolated 15 to 20 knots possible near San Pedro and Point Mugu.

Watches, Warnings, Advisories

Ca, Wind Advisory in effect until 3 AM PDT Wednesday for zones 53-54-349-351. (See LAXNPWLOX). Wind Advisory in effect from noon today to 9 PM PDT this evening for zone 59. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 2 PM this afternoon to 3 AM PDT Wednesday for zones 645-650. (See LAXMWWLOX). Small Craft Advisory in effect until 2 PM PDT this afternoon for zone 670. (See LAXMWWLOX). Gale Warning in effect from 2 PM this afternoon to 6 AM PDT Wednesday for zone 670. (See LAXMWWLOX). Gale Warning in effect until 6 AM PDT Wednesday for zones 673-676. (See LAXMWWLOX).

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