Swell Matrix

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard Ca

152 pm PST Tue Nov 12 2019


12/126 PM.

Above normal temperatures are expected with mostly sunny skies for this afternoon. Expect coastal clouds to move onshore overnight and linger for the morning on Wednesday. It will be cloudy and cooler for late Wednesday into Thursday. Temperatures will trend warmer Friday and into the weekend as clouds decrease.

Short Term

(tdy-Fri), 12/126 PM.

Temps warmed up several degrees inland today due to strong high pressure aloft and light offshore flow. However that influence was negligible at the coast where a cool sea breeze kept temps much closer to Monday's readings. High pressure will still dominate the weather tomorrow and maintain a shallow (<=1000') marine layer for coastal zones but onshore trends will likely result in a few degrees of cooling for coastal valleys. We'll also see increasing high clouds tomorrow from a system several hundred miles offshore but those won't initially have much impact.

Wednesday night into Thursday those high clouds are expected to thicken up quite a bit and keep skies mostly cloudy. Between that and the cooling aloft associated with the approaching trough temperatures area-wide are expected to cool several degrees, but more so across inland areas.

High clouds expected to move east of the area Friday but additional energy will drop into the trough west of the California coast resulting in the eventual formation of a cut off low about 1000 miles southwest of LAX. Skies will generally be clear after any morning marine layer but only a 1-2 degree warmup expected despite the increased sunshine.

Long Term

(Sat-Tue), 12/149 PM.

High pressure building over the eastern Pacific and west coast this weekend is expected to push the cut off low to the west rendering it a non-factor locally. At the same time gradients will be trending offshore again with a little upper support coming in Saturday night into early Sunday to kick up some Santa Ana winds. Temps will warm up several degrees over the weekend as a result with 80s common and possibly even some low 90s for the warmer valleys. Winds may reach low end advisory levels for parts of LA/Ventura Counties Sunday morning.

The ridge breaks down early next week as another trough approaches from the northwest. Cooler temps and the return of the marine layer are likely.

There are hints of a pattern change later next week but there's a lot of uncertainty in the models. The ECMWF ensembles seem to favor keeping the eastern Pacific ridge in place with inside sliders dropping out of Canada into the Great Basin. These still could bring some rain but generally systems from this pattern are lacking in moisture. In any case, there's pretty high confidence in a cooler pattern but low confidence on rain chances.



At 1705Z at KLAX, the marine layer was around 800 feet deep. The top of the inversion was at 2000 feet with a temperature of 23 C.

Low confidence in all coastal TAFs, but moderate confidence elsewhere. A very shallow marine layer combined with very weak pressure gradients and resultant winds will create persistent ceiling and visibility complexities after VFR conditions this afternoon. For tonight and Wednesday morning, IFR conditions will arrive in coastal sections early in the evening and steadily deteriorate to LIFR or VLIFR overnight before improving to IFR Wednesday morning. It also appears that the marine layer will again take quite a bit of time to clear Wednesday morning with many locations not clearing until after 18Z. KLAX, Low confidence in 18z TAF. Cigs may fluctuate between IFR and MVFR through 16Z. There is a 30% chance of 6SM HZ SCT010 conds at 17Z. Low confidence in timing of low clouds tonight. Good confidence that any east wind component will be 5 kt or less.

KBUR, Moderate confidence in 18z TAF. There is a 20% chance of low clouds tonight after 10Z.


12/129 PM.

For all of the coastal waters, high confidence that winds and seas will remain below Small Craft Advisory (SCA) level through Thursday. Moderate confidence that SCA level winds may impact the offshore waters along the Central Coast and southward towards San Nicolas Island on Friday and Saturday.

Patchy dense fog with visibility of one nautical mile may impact all of the coastal waters this morning.

A large and long period NW swell is likely to impact the coastal waters Friday into the weekend, but low confidence on timing and strength.

Watches, Warnings, Advisories


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